Outline of course, Part I: Divergence-measure fields, the solvability of divf = T and the dual of
|
|
- Mary Evans
- 5 years ago
- Views:
Transcription
1 Outline of course, Part I: Divergence-measure fields, the solvability of divf = T and the dual of BV Monica Torres Purdue University Outline of course, Part I: Divergence-measure fields, the solvability of divf = T and the dual ofbv p. 1/49
2 The equation divf = T The solvability of the equation divf = T is connected to the problem of characterizing BV, the dual of the space of functions of bounded variation, BV. Phuc-Torres, Annali de la Scuola Normale Superiore di Pisa, When the right hand side T is a measure µ, then F is called a divergence-measure field. Divergence-measure fields naturally appear in the field of hyperbolic conservation laws. Characterizations of the solvability of divf = µ in the spaces L p (R N ) or C(U): Phuc-T., IUMJ If F L p (R N ) and divf = µ, we can study properties of F. In particular, the existence of normal traces and Gauss-Green formulas for divergence-measure fields: Anzellotti, Anal. Mat. Pure Appl., 1983; Chen-Frid, ARMA 1999, Comm. Math. Phys., 2003; Chen-T., ARMA 2005; Chen-T.-Ziemer, CPAM, 2009; Šilhavý, Rend. Sem. Mat. Padova, 2005; Ambrosio-Crippa-Maniglia, Ann. Fac. Sci. Toulouse, 2005; Frid, 2014; Comi-Chen-Torres, 2017 Outline of course, Part I: Divergence-measure fields, the solvability of divf = T and the dual ofbv p. 2/49
3 The space BV Let Ω be any open set. The space of functions of bounded variation, denoted as BV(Ω), is defined as the space of all functions u L 1 (Ω) such that the distributional gradient Du is a finite vector-valued measure in Ω. The space BV(Ω) is a Banach space with the norm u BV (Ω) = u L 1 (Ω) + Du (Ω). For the case when Ω = R N we will equip BV(R N ) with the norm given by u BV (R N ) = Du (RN ). (1) Another BV -like space is BV N (R N ), defined as the space of all functions in L N (R N ) such that Du is a finite vector-valued measure. The space BV N (R N ) is a Banach space when equipped with the norm u BV N (R N ) = Du (RN ). We remark that BV(R N ) is not a Banach space with the norm (1). Outline of course, Part I: Divergence-measure fields, the solvability of divf = T and the dual ofbv p. 3/49
4 What is known about BV All positive measures in BV(R N ) were characterized by Meyers- Ziemer ( Amer. J. Math., 1977): µ BV(R N ) if and only if µ(b(x,r)) Mr for every r > 0 and x R N. All signed measures in BV(R N ) where characterized by Phuc-T. (IUMJ, 2008): A closed subspace of BV N (R N ), denoted as CH 0, was characterized in De Pauw-T. (Proceedings of the Royal Society of Edinburgh, 2011): Thierry De Pauw (IUMJ, 1998) studied the dual of SBV, the space of special functions of bounded variation. In Phuc-Torres (Annali de la Scuola Normale Superiore di Pisa, 2017) and motivated by image processing, we continued the analysis of BV (including bounded domains). In Fusco-Spector, submitted, 2017, the authors give an integral representation of elements of BV, but under the assumption of the continuum hypothesis. Outline of course, Part I: Divergence-measure fields, the solvability of divf = T and the dual ofbv p. 4/49
5 Image processing and BV The space BV is relevant in the field of image processing since the dual norm in BV is needed to estimate the noise of an image (see "Oscillating Patterns in Image Proccessing and Nonlinear Evolution Equations" by Yves Meyer ). Indeed, if f represents an image and the functions u, v are the cartoon and noise respectively, then the function f u v is the texture. The following expression needs to be computed f u v L 2 +λ u BV +µ v BV. Proper characterizations of BV would allow to precisely compute the noise v BV. Outline of course, Part I: Divergence-measure fields, the solvability of divf = T and the dual ofbv p. 5/49
6 Solvability of divf = f and the limiting cases. If u solves u = f L p (U) then N < p < u C 0,1 N p (U). McMullen and Preiss have shown that for some f s in L (even continuous f) the equation div F = f has no Lipschitz solution. For some f s in L 1, equation divf = f has no solution in BV and not even in L N/ (Bourgain-Brezis, JAMS 2003). The equation u = f L N admits a solution u W 2,N and therefore divf = f L N has a solution F W 1,N. However, since W 1,N is not contained in L (limiting case in the Sobolev imbbeding Theorem) one can not conclude that F L. Nirenberg gave the example u(x) = ϕ(x)x 1 log x α, 0 < α < N 1 N where ϕ is smooth supported near 0. One checks that u L N (R N ) and u L loc (RN ) Outline of course, Part I: Divergence-measure fields, the solvability of divf = T and the dual ofbv p. 6/49
7 Solvability of the equation divf = T Solvability of divf = f L N # ([0,1]N ) in the class L ([0,1] N ;R N ) (Bourgain-Brezis, JAMS 2003). Solvability of divf = f L N # ([0,1]N ) in the class L ([0,1] N ;R N ) W 1,N ([0,1] N ;R N ) (Bourgain-Brezis, JAMS 2003). Solvability of divf = T in the space of continuous vector fields C(U;R N ) (De Pauw-Pfeffer, CPAM 2008). They showed that: The equation has a continuous solution if and only if T belongs to a class of distributions, the space of strong charges, denoted as CH N (U). Moreover, L N (U) CH N (U) Outline of course, Part I: Divergence-measure fields, the solvability of divf = T and the dual ofbv p. 7/49
8 The space BV N (R N ) We let BV N (R N ) denote the linear subspace of L(R N N ) consisting of those functions u whose distributional gradient Du is a finite vector valued measure; i.e., Du M(R N ;R N ). { } Du M = Du (R N ) = sup udivf : F D(R N ;R N ) and F 1 R N <. BV N (R N ) is a Banach space with the norm u BV N (R N ) = u L N (R N )+ Du (R N ). We will work with the equivalent norm u BV N (R N ) := Du M. Outline of course, Part I: Divergence-measure fields, the solvability of divf = T and the dual ofbv p. 8/49
9 The space of charges vanishing at infinity CH 0 (R N ) Definition. Given a sequence{u j } inbv N (R N ) we writeu j 0 whenever sup j Du j M < ; u j 0 weakly inl N (R N ). A charge vanishing at infinity is a linear functionalf : BV N (R N ) R such that u j,f 0 wheneveru j 0. The collection of these is denotedch 0 (R N ). The compactness in BV N (R N ) implies F CH0 := sup{ u,f : u BV N (R N ) and Du M 1} <. and hence CH0 is a norm on CH 0 (R N ). CH 0 (R N ) BV N (R N ) CH 0 (R N ) with the norm CH0 is a Banach space. Outline of course, Part I: Divergence-measure fields, the solvability of divf = T and the dual ofbv p. 9/49
10 The divergence operator Define: div : C 0 (R N ;R N ) CH 0 (R N ) div(f) : BV N (R N ) R, F C 0 (R N ;R N ) div(f)(u) = F,d(Du), u BV N (R N ). R N Proposition. GivenF C 0 (R N ;R N ) one hasdiv(f) CH 0 (R N ) and div : C 0 (R N ;R N ) CH 0 (R N ) is a bounded linear operator: div(f) CH0 F. Question: Is the divergence operator on-to? Outline of course, Part I: Divergence-measure fields, the solvability of divf = T and the dual ofbv p. 10/49
11 Characterization of the solvability of divf = T in C 0 (R N,R N ) Theorem[DePauw-T.] There exists F C 0 (R N ;R N ) such that divf = T if and only if T CH 0 (R N ). Since CH 0 (R N ) BV N (R N ), we have then characterized a closed subspace of BV N (R N ). Since L N (R N ) CH 0 (R N ) the theorem implies that to each f L N (R N ) there corresponds a continuous vector field, vanishing at infinity, F C 0 (R N ;R N ) such that divf = f weakly. Outline of course, Part I: Divergence-measure fields, the solvability of divf = T and the dual ofbv p. 11/49
12 Proof of the theorem CH 0 (R N ) ev div C 0 (R N ;R N ) BV N (R N ) D M(R N ;R N ) Let {α j } be a sequence in CH 0 (R N ) such that div (α j ) µ. Let {u j } in BV N (R N ) such that α j = ev(u j ). div (α j ) M = (div ev)(u j ) M = Du j M. Since {Φ (α j )} is bounded then sup j Du j M <. Then, there exists a subsequence {u jk } and u BV N (R N ) such that u u jk 0. F,d(Du) = udivf = lim R N R N k u jk divf = lim R N k F,d(Du jk ). R N Then R N F,d(Du) = R N F,dµ since Du j µ. From here we conclude Du = µ. Outline of course, Part I: Divergence-measure fields, the solvability of divf = T and the dual ofbv p. 12/49
13 BVc (R N ) is dense in BV N (R N ) Lemma (Phuc-T). Let u BV N (R N ), u 0, and φ k C c (RN ) be a sequence of smooth functions satisfying: 0 φ k 1, φ k 1 onb k (0), φ k 0 onr N \B 2k (0) and Dφ k c/k. Then and for each fixed k > 0 we have lim k (φ ku) u BV N (R N ) = 0, lim j (φ ku) j φ k u BV N (R N ) = 0. In particular, BV c (R N ) is dense in BV N (R N ). Outline of course, Part I: Divergence-measure fields, the solvability of divf = T and the dual ofbv p. 13/49
14 Proof of the density The product rule for BV functions gives that φ k u BV N (R N ) and D(φ k u) = φ k Du+uDφ k (as measures). Thus R N D(uφ k u) = φ k Du Du+uDφ k R N φ k 1 Du + R N R N φ k 1 Du + c k R N φ k 1 Du + c k R N φ k 1 Du +c R N supp(dφ k ) u B 2k \B k ( ( B 2k \B k u B 2k \B k u u Dφ k ) N N ) N N. B 2k \B k 1 N Outline of course, Part I: Divergence-measure fields, the solvability of divf = T and the dual ofbv p. 14/49
15 Proof of the density On the other hand, the coarea formula for BV functions yields R N D(φ k u (φ k u) j) = = = = j H ( {φ k u (φ k u) j > t})dt H ( {φ k u j > t})dt H ( {φ k u > j +t})dt H ( {φ k u > s})ds. Here F stands for the reduced boundary of a set F. Since 0 H ( {φ k u > s})ds <, the Lebesgue dominated convergence theorem yields that the limit, as j, is 0 (for each fixed k > 0). By the triangle inequality, each nonnegativeu BV N (R N ) can be approximated by a function in BV c (R N ). By considering the positive and negative parts of a function u BV N (R N ), the density of BV c (RN ) in BV N (R N ) follows. Outline of course, Part I: Divergence-measure fields, the solvability of divf = T and the dual ofbv p. 15/49
16 BV(R N ) and BV N (R N ) are isometrically isomorphic BV(R N ) BV N (R N ) since u N L (R N ) C(N) Du (R N ), u BV(R N ) We define the map as S : BV N (R N ) BV(R N ) S(T) = T LBV(R N ) S is an isometry as a consequence of our Lemma: BV c (R N ) is dense inbv N (R N ) Notice also that BV c (RN ) is dense inbv(r N ). Outline of course, Part I: Divergence-measure fields, the solvability of divf = T and the dual ofbv p. 16/49
17 The Homogeneous Sobolev space Ẇ1,1 (R N ) Definition: Let Ẇ 1,1 (R N ) denote the space of all functions u L N (R N ) such that Du L 1 (R N ). Equivalently, the space Ẇ1,1 (R N ) can also be defined as the closure of C c (R N ) in BV N (R N ) (i.e. in the norm Du L 1 (R N ) ). Thus, u Ẇ1,1 (R N ) if and only if there exists a sequence u k C c (R N ) such that R N D(u k u) 0. We remark that Ẇ 1,1 (R N ) is denoted as G by Y. Meyer in his book Oscillating Patterns in Image Processing and Nonlinear Evolution Equations. The space G plays a key role in modeling the oscillatory nature of noise and texture in images. We have Ẇ 1,1 (R N ) BV N (R N ). It is noted in Meyer s book that, since the space G is simpler than BV N (R N ), the space G = Ẇ1,1 (R N ) is used instead of BV N (R N ). Our main theorem shows that the measures in G coincide with the measures in BV N (R N ). Moreover, all the (signed) measures in BV N (R N ) can be characterized. Outline of course, Part I: Divergence-measure fields, the solvability of divf = T and the dual ofbv p. 17/49
18 Measures in Ẇ1,1 (R N ) and BV N (R N ) Definition: We let M loc Ẇ 1,1 (R N ) := {T Ẇ 1,1 (R N ) : T(ϕ) = R N ϕdµ, µ M loc (R N ), ϕ C c (RN )}. Therefore, if µ M loc (R N ) Ẇ1,1 (R N ), the action < µ,u > can be uniquely defined for all u Ẇ1,1 (R N ) (because of the density of C c (RN ) in Ẇ1,1 (R N )). Definition: We let M loc BV N (R N ) := {T BV N (R N ) : T(ϕ) = R N ϕ dµ, µ M loc, ϕ BV c }, where ϕ is the precise representative in BV c (R N ). Thus, if µ M loc BV N (R N ), the action < µ,u > can be uniquely defined for all u BV N (R N ) Outline of course, Part I: Divergence-measure fields, the solvability of divf = T and the dual ofbv p. 18/49
19 Characterization of G = Ẇ1,1 (R N ) Theorem: The distribution T belongs to Ẇ1,1 (R N ) if and only if T = divf for some vector field F L (R N,R N ). Moreover, T Ẇ1,1 (R N ) = min{ F L (R N,R N ) }, where the minimum is taken over all F L (R N,R N ) such that divf = T. Here we use the norm F L (R N,R N ) := (F 2 1 +F F2 N )1/2 L (R N ) for F = (F 1,...,F N ). Proof: It is easy to see that if T = divf where F L (R N,R N ) then T Ẇ1,1 (R N ) with T Ẇ1,1 (R N ) F L (R N,R N ). Conversely, let T Ẇ1,1 (R N ). Define A : Ẇ 1,1 (R N ) L 1 (R N,R N ), A(u) = Du, Outline of course, Part I: Divergence-measure fields, the solvability of divf = T and the dual ofbv p. 19/49
20 Let T Ẇ1,1 (R N ). We have A : Ẇ 1,1 (R N ) L 1 (R N,R N ), A(u) = Du. The range of A, denoted as R(A), is a closed subspace of L 1 (R N,R N ) since Ẇ 1,1 (R N ) is complete. Define T 1 : R(A) R, T 1 (Du) = T(u), for each Du R(A). Then we have T 1 R(A) = T Ẇ1,1 (R N ). By Hahn-Banach Theorem there exists a norm-preserving extension T 2 of T 1 to all L 1 (R N,R N ). On the other hand, by the Riesz Representation Theorem for vector valued functions there exists a vector field F L (R N,R N ) such that T 2 (v) = R N F v, for every v L 1 (R N,R N ), and F L (R N,R N ) = T 2 L 1 (R N,R N ) = T 1 R(A) = T Ẇ1,1 (R N ). Outline of course, Part I: Divergence-measure fields, the solvability of divf = T and the dual ofbv p. 20/49
21 In particular, for each ϕ C c (RN ) we have T(ϕ) = T 1 (Dϕ) = T 2 (Dϕ) = R N F Dϕ, which yields with T = div( F), F L (R N,R N ) = T Ẇ 1,1 (R N ). Outline of course, Part I: Divergence-measure fields, the solvability of divf = T and the dual ofbv p. 21/49
22 Characterization of measures in BV N (R N ). Theorem 1 (Phuc-T.) Let µ M loc (R N ) be a locally finite signed measure. The following are equivalent: (i) There exists a vector field F L (R N,R N ) such that divf = µ in the sense of distributions. (ii) There is a constant C such that µ(u) CH ( U) for any smooth bounded open (or closed) set U with H ( U) < +. (iii) H (A) = 0 implies µ (A) = 0 for all Borel sets A and there is a constant C such that, < µ,u > := u dµ C Du, u BV R N R N c (R N ), where u is the representative in the class of u that is defined H -almost everywhere. (iv) µ BV N (R N ). The action of µ on any u BV N (R N ) is defined (uniquely) as < µ,u >:= lim < µ,u k >= u k R N k dµ, whereu k BVc (R N ),u k u inbv N (R N ) Outline of course, Part I: Divergence-measure fields, the solvability of divf = T and the dual ofbv p. 22/49
23 In particular, if u BV c (RN ) then < µ,u >= R N u dµ, and moreover, if µ is a non-negative measure then, for all u BV N (R N ), < µ,u >= R N u dµ. Outline of course, Part I: Divergence-measure fields, the solvability of divf = T and the dual ofbv p. 23/49
24 The measures in BV N (R N ) coincide with the measures in Ẇ1,1 (R N ) Theorem 1.2 (Phuc,T.): Let E := M loc (R N ) BV N (R N ) and F := M loc (R N ) Ẇ1,1 (R N ). Then E and F are isometrically isomorphic. Proof: We define S : E F, S(T) = T LẆ1,1. Clearly, T is a linear map. Assume that S(T) = 0 F for some T E. Then T(u) = 0, for all u Ẇ 1,1 (R N ). (2) Thus, if µ is the measure associated to T E, then R N ϕdµ = T(ϕ) = 0 for all ϕ C c (R N ), which implies thatµ = 0. (3) Now, by definition of E, we have T(u) = R N u dµ = 0, for all u BV c (RN ), and by density: T 0 on BV N (R N ). Outline of course, Part I: Divergence-measure fields, the solvability of divf = T and the dual ofbv p. 24/49
25 S is on-to Take H F. Thus, there exists µ M loc (R N ) such that ϕdµ = H(ϕ), for all ϕ C R N c (RN ), Since H Ẇ1,1 (R N ), there exists a bounded vector field F L (R N,R N ) such that divf = µ in the sense of distributions and H Ẇ1,1 (R N ) = µ Ẇ1,1 (R N ) = F L (R N,R N ) From our Theorem1: µ << H and µ(u) F H ( U), for all open sets U R N, (4) and u dµ F R N L (R N,R N ) u BVc (RN ), for all u BV c (R N ), (5) Outline of course, Part I: Divergence-measure fields, the solvability of divf = T and the dual ofbv p. 25/49
26 S is an isometry Hence, µ BV c (R N ) = F L (R N,R N ). From Theorem1, it follows that µ can be extended to a continuous linear functional ˆµ BV N (R N ) and clearly, S(ˆµ) = µ, which implies that T is surjective. This extension preserves the operator norm and thus S(ˆµ) Ẇ1,1 (R N ) = ˆµ BV N (R N ) = F L (R N,R N ), which shows that E and F are isometrically isomorphic. Outline of course, Part I: Divergence-measure fields, the solvability of divf = T and the dual ofbv p. 26/49
27 A formula to compute µ BV N (R N ) The space Ẇ1,1 (R N ) is denoted as the G space in image processing, and it plays a key role in modeling the noise of an image. It is more convenient to work with G instead of BV N (R N ). Indeed, the full characterization of BV N (R N ) is unknown. However, G can be easily characterized. Our previous results show that, when restricted to measures, both spaces coincide. Moreover, the norm of any (signed) measure µ G can be computed as µ G = sup U R N µ(u) H ( U), (6) where the sup is taken over all open sets U R N with smooth boundary and H ( U) < +. Hence, our results give an alternative to the more abstract computation of µ G : µ G = min{ F L (R N,R N ) }, where the minimum is taken over all F L (R N,R N ) such that divf = T. We refer the reader to Kindermann-Osher-Xu for an algorithm based on the level set method to compute (6) for the case when µ is a function f L 2 (R 2 ) with zero mean. Outline of course, Part I: Divergence-measure fields, the solvability of divf = T and the dual ofbv p. 27/49
28 The dual of BV 0 (Ω) Let Ω be a bounded open set with Lipschitz continuous boundary Ω and let u BV(Ω). Then, there exists a function ϕ L 1 ( Ω) such that, for H -almost every x Ω, lim r 0 r N B(x,r) Ω u(y) ϕ(x) dy = 0. From the construction of the trace ϕ, we see that ϕ is uniquely determined. Therefore, we have a well defined operator γ 0 : BV(Ω) L 1 ( Ω). We now define the space BV 0 (Ω) as follows: Definition: Let BV 0 (Ω) = ker(γ 0 ). Outline of course, Part I: Divergence-measure fields, the solvability of divf = T and the dual ofbv p. 28/49
29 Strict Convergence in BV(Ω) Definition: Let {u k } BV(Ω) and u BV(Ω). We say that u k converges to u in the sense of intermediate (or strict) convergence if u k u strongly inl 1 (Ω) and Ω Du k Ω Du. We also define another BV function space with a zero boundary condition. Definition: Let BV 0 (Ω) := C c (Ω), where the closure is taken with respect to the strict convergence of BV(Ω). The following well known results will be very useful: Theorem: The trace operator γ 0 is continuous from BV(Ω) equipped with the intermediate convergence onto L 1 ( Ω) equipped with the strong convergence. Theorem: The space C (Ω) BV(Ω) is dense in BV(Ω) equipped with the intermediate convergence. Outline of course, Part I: Divergence-measure fields, the solvability of divf = T and the dual ofbv p. 29/49
30 The space BV 0 (Ω) Theorem 2 (Phuc-T.): BV 0 (Ω) = BV 0 (Ω). Proof: Let u BV 0 (Ω). Thus, there exists a sequence {u k } C c (Ω) such that u k u in L 1 (Ω) and Du k Ω Ω Du Since u k C c (Ω) then γ 0 (u k ) 0. The continuity of the trace operator implies γ 0 (u k ) γ(u) in L 1 ( Ω), and hence γ(u) = 0 and u BV 0 (Ω). On the other direction, let u BV 0 (Ω). The key point in this proof is to show that BV c (Ω) is dense in BV 0 (Ω) in the strong topology of BV(Ω). Thus, there exists a sequence u k BV c (Ω) such that u k u inl 1 (Ω), lim k Ω Du k Du = 0 Outline of course, Part I: Divergence-measure fields, the solvability of divf = T and the dual ofbv p. 30/49
31 Given a sequence ε k 0, we consider the sequence of mollifications w k := u k ρ εk. We can choose ε k sufficiently small to have w k C c (Ω). Also, for each k, lim D(u k ρ ε ) = ε 0 Ω Ω Du k, lim u k ρ ε u k = 0. ε 0 Ω Thus we can choose ε k small enough so that, for each k, Ω D(u k ρ εk ) = Ω Du k +α(k), where α k 1 and 2k, Ω u k ρ εk u k 1 2 k Outline of course, Part I: Divergence-measure fields, the solvability of divf = T and the dual ofbv p. 31/49
32 lim w k u lim w k u k + lim u k u = 0. k Ω k Ω k Ω Also, letting k we obtain lim Dw k = lim D(u k ρ εk ) = k Ω k Ω Ω Du. we conclude that w k u in the strict convergence which implies that u BV 0 (Ω). Outline of course, Part I: Divergence-measure fields, the solvability of divf = T and the dual ofbv p. 32/49
33 BV c (Ω) is dense in BV 0 (Ω) Theorem: Let Ω be any bounded open set with Lipschitz boundary. Then BV c (Ω) is dense in BV 0 (Ω) in the strong topology of BV(Ω). Proof: We consider first the case u BV 0 (C R,T ), where C R,T is the open cylinder C R,T = B R (0,T), B R is an open ball of radius R in R, and supp(u) C R,T = supp(u) (B R {0}). A generic point in C R,T will be denoted by (x,t), with x B R and t (0,T). We can approximate u with a sequence of functions u k C (C R,T ) such that u k u inl 1 (C R,T ) and C R,T Du k C R,T Du. The condition supp(u) C R,T = supp(u) (B R {0}) implies that γ 0 (u k ) ( CR,T \(B R {0})) 0. By continuity of the trace operator, γ 0 (u k ) γ 0 (u) inl 1 ( C R,T ) and hence Outline of course, Part I: Divergence-measure fields, the solvability of divf = T and the dual ofbv p. 33/49
34 and hence, γ 0 (u k ) (BR {0}) = u k (BR {0}) 0 inl1 (B R {0}). u k (x,x n ) u k (x,0) = xn u k (x,x n ) u k (x,0) + We integrate both sides to obtain: B R u k (x,x n ) dx 0 u k x n (x,t)dt, x B R, 0 x n T xn 0 B R u k (x,0) dx + u k,(x,t) x dt. n xn 0 B R Du k (x,t) dx dt. Letting k we obtain u(x,x n ) dx B R xn 0 B R Du = Du (B R (0,x n )) for a.e. 0 < x n < T. Outline of course, Part I: Divergence-measure fields, the solvability of divf = T and the dual ofbv p. 34/49
35 Consider a function ϕ C c (R) such that ϕ is decreasing in [0,+ ) and satisfies ϕ 1 on[0,1],ϕ 0 onr\[ 1,2],0 ϕ 1. We define ϕ k (t) = ϕ(kt), k = 1,2,... v k (x,t) = (1 ϕ k (t))u(x,t) Moreover, v k t = (1 ϕ k ) u t kϕ (kt)u, D x v k = (1 ϕ k )D x u. Thus we have C R,T Dv k Du = = C R,T C R,T ( D x u ϕ k D x u, u t ϕ u ) ( k t kϕ (kt)u D x u, u ) t ( u ) ϕ k D x u, ϕ k t kϕ (kt)u. Outline of course, Part I: Divergence-measure fields, the solvability of divf = T and the dual ofbv p. 35/49
36 Since ϕ k (t) = 0 for t > 2 k we have the following: ( ) Dv k Du C ϕ k Du + k ϕ (kx n ) u C R,T C R,T C R,T C C C = C = C 2/k 0 2/k 0 2/k 0 2/k 0 2/k 0 Du +Ck B R Du +Ck B R 2/k 0 2/k 0 B R u(x,t) dx dt Du (B R (0,t))dt, Du +Ck Du (B R (0,2/k)) B R Du +Ck 2 2/k B R k Du 0 B R Du. B R 2/k 0 dt Outline of course, Part I: Divergence-measure fields, the solvability of divf = T and the dual ofbv p. 36/49
37 A Sobolev inequality for functions in BV 0 (Ω) As a corollary of our theorem we have: Theorem: Let u BV 0 (Ω). Then u L N (Ω) C Du (Ω) for a constant C = C(n). Remark 1: For the next theorems, we equip BV 0 (Ω) and W 1,1 0 (Ω) with the following equivalent norms: u BV0 (Ω) = Du (Ω), u W 1,1 0 (Ω) = Ω Du dx Remark 2: By truncating the function as before, we obtain that BVc (Ω) is dense in BV 0 (Ω). Outline of course, Part I: Divergence-measure fields, the solvability of divf = T and the dual ofbv p. 37/49
38 Measures in W 1,1 0 (Ω) and BV 0 (Ω) Definition. For a bounded open set Ω with Lipschitz boundary, we let M loc (Ω) W 1,1 0 (Ω) := {T W 1,1 0 (Ω) : T(ϕ) = Ω ϕdµ,µ M loc (Ω), ϕ C c (Ω)}. Therefore, if µ M loc (Ω) W 1,1 0 (Ω), then the action < µ,u > can be uniquely defined for all u W 1,1 0 (Ω) (because of the density of Cc (Ω) in W 1,1 0 (Ω)). Definition For a bounded open set Ω with Lipschitz boundary, we let M loc (Ω) BV 0 (Ω) := {T BV 0 (Ω) : T(ϕ) = Ω ϕ dµ,µ M loc (Ω), ϕ BV c (Ω)}, where ϕ is the precise representative of ϕ. Thus, if µ M loc (Ω) BV 0 (Ω), then the action < µ,u > can be uniquely defined for all u BV 0 (Ω) (because of the density of BV c (Ω) in BV 0(Ω)). Outline of course, Part I: Divergence-measure fields, the solvability of divf = T and the dual ofbv p. 38/49
39 Characterization of measures in BV 0 (Ω) Theorem 3 (Phuc,T.): Let Ω be any bounded open set with Lipschitz boundary and µ M loc (Ω). Then, the following are equivalent: (i) There exists a vector field F L (Ω,R n ) such that divf = µ. (ii) µ(u) C H n 1 ( U) for any smooth open (or closed) set U Ω with H n 1 ( U) < +. (iii) H n 1 (A) = 0 implies µ (A) = 0 for all Borel sets A Ω and there is a constant C such that, for all u BV c (Ω), < µ,u > := Ω u dµ C Ω Du, whereu is the representative in the class of u that is definedh n 1 -almost everywhere. (iv) µ BV 0 (Ω). The action of µ on any u BV 0 (Ω) is defined (uniquely) as < µ,u >:= lim < µ,u k >= lim u k dµ, k k Ω where u k BV c (Ω) converges to u in BV 0 (Ω). Outline of course, Part I: Divergence-measure fields, the solvability of divf = T and the dual ofbv p. 39/49
40 In particular, if u BVc (Ω) then < µ,u >= Ω u dµ, and moreover, if µ is a non-negative measure then, for all u BV 0 (Ω), < µ,u >= u dµ. Ω Outline of course, Part I: Divergence-measure fields, the solvability of divf = T and the dual ofbv p. 40/49
41 The measures in BV(Ω) coincide with the measures in W 1,1 0 (Ω) Theorem 3.1 (Phuc-T.): The normed spaces M loc (Ω) BV 0 (Ω) and M loc (Ω) W 1,1 0 (Ω) are isometrically isomorphic. The characterization of the measures in BV(Ω) is more challenging since, in this case, we need to consider the space BV(Ω) with the full norm: u BV (Ω) = u L ( Ω) + Du (Ω). However, we can prove the following: Theorem: Let µ be a finite signed measure in Ω. Extend µ by zero to R n \Ω by setting µ(r n \Ω) = 0. Then, µ BV(Ω) if and only if µ(u) C H n 1 ( U), for every smooth open set U R n and a constant C = C(Ω,µ). Outline of course, Part I: Divergence-measure fields, the solvability of divf = T and the dual ofbv p. 41/49
42 f BV(R N ) but f / BV(R N ) Proposition: Let f(x) = ǫ x 1 ǫ sin( x ǫ )+(n 1) x 1 cos( x ǫ ), where 0 < ǫ < n 1 is fixed. Then f(x) = div[x x 1 cos( x ǫ )]. Moreover, there exists a sequence {r k } decreasing to zero such that B rk (0) f + (x)dx cr n 1 ǫ k for a constant c = c(n,ǫ) > 0 independent of k. Here f + is the positive part of f. Thus by Theorem 1 we see that f belongs to BV(R N ), whereas f does not. This result resolves a question raised by Meyers and Ziemer in their classical paper " Integral inequalities of Poincare and Wirtinger type for BV functions", Amer. J. Math., Outline of course, Part I: Divergence-measure fields, the solvability of divf = T and the dual ofbv p. 42/49
43 A constructive approach of bounded solutions In the paper Hierarchical construction of bounded solutions in critical regularity spaces, CPAM), Tadmor presents another duality-based approach for the existence of bounded solutions to divf = f,f L N # ([0,1]N ). His approach is constructive, meaning that the solution F is constructed as a hierarchical sum, F = F j, where the {F j } s are computed recursively as appropiate minimizers, for j = 0,1,... F j+1 = arginf F F L +λ 1 2 j f div j k=1 F k divf N L N, Outline of course, Part I: Divergence-measure fields, the solvability of divf = T and the dual ofbv p. 43/49
44 Solvability of divf = µ in L p (R N,R N ), p. Theorem (Phuc-T.) div F = µ µ non-negative measure, has a global solution in F L p (R N,R N ), 1 p N, if and only if µ 0. Moreover, for N < p <, the equation has a solution if and only if I 1 µ L p (R N ), where I 1 µ is the Riesz potential of order 1 of µ defined by 1 I 1 µ(x) = R x y dµ(y), x RN. N Outline of course, Part I: Divergence-measure fields, the solvability of divf = T and the dual ofbv p. 44/49
45 Solvability for divf = µ in C(U;R N ) Theorem (Phuc-T.). Let µ be a non-negative measure on a nonempty open setu R N. Then the following are equivalent. The equationdivf = µ has a continuous solution F : U R N. Givenε > 0 and a compact setk U, there isθ > 0 such that ϕdµ ε ϕ dx+θ ϕ dx, ϕ C R R N N R N 0 (R N ), sptϕ K. For any compact setk U, lim r 0 µ(b r (x)) r = 0,x K, and this limit is uniform. Outline of course, Part I: Divergence-measure fields, the solvability of divf = T and the dual ofbv p. 45/49
46 Removable singularities of divf = 0 Given the space of vector fields F and S R N a closed set, it is said that the set S is F-removable for the equation divf = 0 if whenever F F satisfies divf = µ in R N \S, then divf = µ in R N. Outline of course, Part I: Divergence-measure fields, the solvability of divf = T and the dual ofbv p. 46/49
47 Application to the removable of singularities: L p case Theorem (Phuc-T): Let E be a compact set contained in an open set U R N. Let N µ M(U) such that µ(e) = 0, and let < p. If cap 1,p (E) = 0 then every solution F to divf = µ inu \E, F L p loc (U) (7) is a solution to divf = µ inu, F L p loc (U). (8) Conversely, assume there is at least one vector field F that solves (8) and suppose that every solution to (7) is also a solution to (8), then necessarily cap 1,p (E) = 0. We recall that cap 1,1 (E) = 0 if and only if H (E) = 0. Therefore, S is L -removable if and only if H (S) = 0. Outline of course, Part I: Divergence-measure fields, the solvability of divf = T and the dual ofbv p. 47/49
48 Application to the removable of singularities: continuous case Theorem (Phuc-T): Let E be a compact set contained in an open set U R N. Let µ M(U) such that µ(e) = 0. If H (E) = 0 then every solution F to divf = µ inu \E, F C(U) (9) is a solution to divf = µ inu, F C(U). (10) Conversely, assume there is at least one vector field F that solves (10) and suppose that every solution to (9) is also a solution to (10), then H +ǫ (E) = 0 for any ǫ > 0. That is, the Hausdorff dimension of E cannot exceed N 1. Outline of course, Part I: Divergence-measure fields, the solvability of divf = T and the dual ofbv p. 48/49
49 Related results in this direction Moonens, Real Anal. Exchange, Moonens-Valeriola, Removable sets for the flux of continuous vector fields, Proc. Amer. Math. Soc., 2010). Moonens-Russ-Tuominen, Removable singularities for div v = f in weighted Lebesgue spaces, Ponce, IUMJ, S is removable if and only if S is σ-finite with respect to H. Ponce-Spector, A boxing inequality for the fractional perimeter, Proved a fractional boxing inequality and used the existence theorems for divergence-measure fields to obtain a trace inequality in fractional Sobolev spaces. Outline of course, Part I: Divergence-measure fields, the solvability of divf = T and the dual ofbv p. 49/49
On the distributional divergence of vector fields vanishing at infinity
Proceedings of the Royal Society of Edinburgh, 141A, 65 76, 2011 On the distributional divergence of vector fields vanishing at infinity Thierry De Pauw Institut de Recherches en Mathématiques et Physique,
More informationFUNCTIONS OF BOUNDED VARIATION AND SETS OF FINITE PERIMETER
FUNCTIONS OF BOUNDED VARIATION AND SETS OF FINITE PERIMETER MONICA TORRES Abstract. We present in these notes some fine properties of functions of bounded variation and sets of finite perimeter, which
More informationDivergence-measure fields: an overview of generalizations of the Gauss-Green formulas
Divergence-measure fields: an overview of generalizations of the Gauss-Green formulas Giovanni E. Comi (SNS) PDE CDT Lunchtime Seminar University of Oxford, Mathematical Institute June, 8, 2017 G. E. Comi
More informationGIOVANNI COMI AND MONICA TORRES
ONE-SIDED APPROXIMATION OF SETS OF FINITE PERIMETER GIOVANNI COMI AND MONICA TORRES Abstract. In this note we present a new proof of a one-sided approximation of sets of finite perimeter introduced in
More informationRecall that if X is a compact metric space, C(X), the space of continuous (real-valued) functions on X, is a Banach space with the norm
Chapter 13 Radon Measures Recall that if X is a compact metric space, C(X), the space of continuous (real-valued) functions on X, is a Banach space with the norm (13.1) f = sup x X f(x). We want to identify
More informationSHARP BOUNDARY TRACE INEQUALITIES. 1. Introduction
SHARP BOUNDARY TRACE INEQUALITIES GILES AUCHMUTY Abstract. This paper describes sharp inequalities for the trace of Sobolev functions on the boundary of a bounded region R N. The inequalities bound (semi-)norms
More informationHOMEOMORPHISMS OF BOUNDED VARIATION
HOMEOMORPHISMS OF BOUNDED VARIATION STANISLAV HENCL, PEKKA KOSKELA AND JANI ONNINEN Abstract. We show that the inverse of a planar homeomorphism of bounded variation is also of bounded variation. In higher
More informationCharacterizations of the Existence and Removable Singularities of Divergence-measure Vector Fields
Characterizations of the Existence and Removable Singularities of Divergence-measure Vector Fields NGYEN CONG PHC & MONICA TORRES ABSTRACT. We study the solvability and removable singularities of the equation
More informationCAUCHY FLUXES AND GAUSS-GREEN FORMULAS FOR DIVERGENCE-MEASURE FIELDS OVER GENERAL OPEN SETS
CACHY FLXES AND GASS-GREEN FORMLAS FOR DIVERGENCE-MEASRE FIELDS OVER GENERAL OPEN SETS GI-QIANG G. CHEN, GIOVANNI E. COMI, AND MONICA TORRES In memoriam William P. Ziemer Abstract. We establish the interior
More informationRegularity and compactness for the DiPerna Lions flow
Regularity and compactness for the DiPerna Lions flow Gianluca Crippa 1 and Camillo De Lellis 2 1 Scuola Normale Superiore, Piazza dei Cavalieri 7, 56126 Pisa, Italy. g.crippa@sns.it 2 Institut für Mathematik,
More informationTHE L 2 -HODGE THEORY AND REPRESENTATION ON R n
THE L 2 -HODGE THEORY AND REPRESENTATION ON R n BAISHENG YAN Abstract. We present an elementary L 2 -Hodge theory on whole R n based on the minimization principle of the calculus of variations and some
More information3. (a) What is a simple function? What is an integrable function? How is f dµ defined? Define it first
Math 632/6321: Theory of Functions of a Real Variable Sample Preinary Exam Questions 1. Let (, M, µ) be a measure space. (a) Prove that if µ() < and if 1 p < q
More informationA NOTE ON THE INITIAL-BOUNDARY VALUE PROBLEM FOR CONTINUITY EQUATIONS WITH ROUGH COEFFICIENTS. Gianluca Crippa. Carlotta Donadello. Laura V.
Manuscript submitted to Website: http://aimsciences.org AIMS Journals Volume, Number, Xxxx XXXX pp. A NOTE ON THE INITIAL-BOUNDARY VALUE PROBLEM FOR CONTINUITY EQUATIONS WITH ROUGH COEFFICIENTS Gianluca
More informationPROBLEMS. (b) (Polarization Identity) Show that in any inner product space
1 Professor Carl Cowen Math 54600 Fall 09 PROBLEMS 1. (Geometry in Inner Product Spaces) (a) (Parallelogram Law) Show that in any inner product space x + y 2 + x y 2 = 2( x 2 + y 2 ). (b) (Polarization
More informationNonlinear aspects of Calderón-Zygmund theory
Ancona, June 7 2011 Overture: The standard CZ theory Consider the model case u = f in R n Overture: The standard CZ theory Consider the model case u = f in R n Then f L q implies D 2 u L q 1 < q < with
More informationBoundary measures, generalized Gauss Green formulas, and mean value property in metric measure spaces
Boundary measures, generalized Gauss Green formulas, and mean value property in metric measure spaces Niko Marola, Michele Miranda Jr, and Nageswari Shanmugalingam Contents 1 Introduction 2 2 Preliminaries
More informationDomains in metric measure spaces with boundary of positive mean curvature, and the Dirichlet problem for functions of least gradient
Domains in metric measure spaces with boundary of positive mean curvature, and the Dirichlet problem for functions of least gradient Panu Lahti Lukáš Malý Nageswari Shanmugalingam Gareth Speight June 22,
More informationReal Analysis Qualifying Exam May 14th 2016
Real Analysis Qualifying Exam May 4th 26 Solve 8 out of 2 problems. () Prove the Banach contraction principle: Let T be a mapping from a complete metric space X into itself such that d(tx,ty) apple qd(x,
More informationNECESSARY CONDITIONS FOR WEIGHTED POINTWISE HARDY INEQUALITIES
NECESSARY CONDITIONS FOR WEIGHTED POINTWISE HARDY INEQUALITIES JUHA LEHRBÄCK Abstract. We establish necessary conditions for domains Ω R n which admit the pointwise (p, β)-hardy inequality u(x) Cd Ω(x)
More informationb i (µ, x, s) ei ϕ(x) µ s (dx) ds (2) i=1
NONLINEAR EVOLTION EQATIONS FOR MEASRES ON INFINITE DIMENSIONAL SPACES V.I. Bogachev 1, G. Da Prato 2, M. Röckner 3, S.V. Shaposhnikov 1 The goal of this work is to prove the existence of a solution to
More informationA Concise Course on Stochastic Partial Differential Equations
A Concise Course on Stochastic Partial Differential Equations Michael Röckner Reference: C. Prevot, M. Röckner: Springer LN in Math. 1905, Berlin (2007) And see the references therein for the original
More informationGRAND SOBOLEV SPACES AND THEIR APPLICATIONS TO VARIATIONAL PROBLEMS
LE MATEMATICHE Vol. LI (1996) Fasc. II, pp. 335347 GRAND SOBOLEV SPACES AND THEIR APPLICATIONS TO VARIATIONAL PROBLEMS CARLO SBORDONE Dedicated to Professor Francesco Guglielmino on his 7th birthday W
More informationNONHOMOGENEOUS ELLIPTIC EQUATIONS INVOLVING CRITICAL SOBOLEV EXPONENT AND WEIGHT
Electronic Journal of Differential Equations, Vol. 016 (016), No. 08, pp. 1 1. ISSN: 107-6691. URL: http://ejde.math.txstate.edu or http://ejde.math.unt.edu ftp ejde.math.txstate.edu NONHOMOGENEOUS ELLIPTIC
More informationOverview of normed linear spaces
20 Chapter 2 Overview of normed linear spaces Starting from this chapter, we begin examining linear spaces with at least one extra structure (topology or geometry). We assume linearity; this is a natural
More informationSobolev Spaces. Chapter 10
Chapter 1 Sobolev Spaces We now define spaces H 1,p (R n ), known as Sobolev spaces. For u to belong to H 1,p (R n ), we require that u L p (R n ) and that u have weak derivatives of first order in L p
More informationContents: 1. Minimization. 2. The theorem of Lions-Stampacchia for variational inequalities. 3. Γ -Convergence. 4. Duality mapping.
Minimization Contents: 1. Minimization. 2. The theorem of Lions-Stampacchia for variational inequalities. 3. Γ -Convergence. 4. Duality mapping. 1 Minimization A Topological Result. Let S be a topological
More informationNotions such as convergent sequence and Cauchy sequence make sense for any metric space. Convergent Sequences are Cauchy
Banach Spaces These notes provide an introduction to Banach spaces, which are complete normed vector spaces. For the purposes of these notes, all vector spaces are assumed to be over the real numbers.
More informationEXISTENCE OF SOLUTIONS FOR KIRCHHOFF TYPE EQUATIONS WITH UNBOUNDED POTENTIAL. 1. Introduction In this article, we consider the Kirchhoff type problem
Electronic Journal of Differential Equations, Vol. 207 (207), No. 84, pp. 2. ISSN: 072-669. URL: http://ejde.math.txstate.edu or http://ejde.math.unt.edu EXISTENCE OF SOLUTIONS FOR KIRCHHOFF TYPE EQUATIONS
More informationMAT 578 FUNCTIONAL ANALYSIS EXERCISES
MAT 578 FUNCTIONAL ANALYSIS EXERCISES JOHN QUIGG Exercise 1. Prove that if A is bounded in a topological vector space, then for every neighborhood V of 0 there exists c > 0 such that tv A for all t > c.
More information3 (Due ). Let A X consist of points (x, y) such that either x or y is a rational number. Is A measurable? What is its Lebesgue measure?
MA 645-4A (Real Analysis), Dr. Chernov Homework assignment 1 (Due ). Show that the open disk x 2 + y 2 < 1 is a countable union of planar elementary sets. Show that the closed disk x 2 + y 2 1 is a countable
More informationHardy spaces associated to operators satisfying Davies-Gaffney estimates and bounded holomorphic functional calculus.
Hardy spaces associated to operators satisfying Davies-Gaffney estimates and bounded holomorphic functional calculus. Xuan Thinh Duong (Macquarie University, Australia) Joint work with Ji Li, Zhongshan
More informationl(y j ) = 0 for all y j (1)
Problem 1. The closed linear span of a subset {y j } of a normed vector space is defined as the intersection of all closed subspaces containing all y j and thus the smallest such subspace. 1 Show that
More informationBrunn-Minkowski inequality for the 1-Riesz capacity and level set convexity for the 1/2-Laplacian
Brunn-Minkowski inequality for the 1-Riesz capacity and level set convexity for the 1/2-Laplacian M. Novaga, B. Ruffini January 13, 2014 Abstract We prove that that the 1-Riesz capacity satisfies a Brunn-Minkowski
More informationON A MAXIMAL OPERATOR IN REARRANGEMENT INVARIANT BANACH FUNCTION SPACES ON METRIC SPACES
Vasile Alecsandri University of Bacău Faculty of Sciences Scientific Studies and Research Series Mathematics and Informatics Vol. 27207), No., 49-60 ON A MAXIMAL OPRATOR IN RARRANGMNT INVARIANT BANACH
More informationDuality in spaces of finite linear combinations of atoms
Duality in spaces of finite linear combinations of atoms arxiv:0809.1719v3 [math.fa] 24 Sep 2008 Fulvio Ricci and Joan Verdera Abstract In this note we describe the dual and the completion of the space
More informationOn uniqueness of weak solutions to transport equation with non-smooth velocity field
On uniqueness of weak solutions to transport equation with non-smooth velocity field Paolo Bonicatto Abstract Given a bounded, autonomous vector field b: R d R d, we study the uniqueness of bounded solutions
More informationBehaviour of Lipschitz functions on negligible sets. Non-differentiability in R. Outline
Behaviour of Lipschitz functions on negligible sets G. Alberti 1 M. Csörnyei 2 D. Preiss 3 1 Università di Pisa 2 University College London 3 University of Warwick Lars Ahlfors Centennial Celebration Helsinki,
More information2 (Bonus). Let A X consist of points (x, y) such that either x or y is a rational number. Is A measurable? What is its Lebesgue measure?
MA 645-4A (Real Analysis), Dr. Chernov Homework assignment 1 (Due 9/5). Prove that every countable set A is measurable and µ(a) = 0. 2 (Bonus). Let A consist of points (x, y) such that either x or y is
More informationEXISTENCE AND REGULARITY RESULTS FOR SOME NONLINEAR PARABOLIC EQUATIONS
EXISTECE AD REGULARITY RESULTS FOR SOME OLIEAR PARABOLIC EUATIOS Lucio BOCCARDO 1 Andrea DALL AGLIO 2 Thierry GALLOUËT3 Luigi ORSIA 1 Abstract We prove summability results for the solutions of nonlinear
More information2 A Model, Harmonic Map, Problem
ELLIPTIC SYSTEMS JOHN E. HUTCHINSON Department of Mathematics School of Mathematical Sciences, A.N.U. 1 Introduction Elliptic equations model the behaviour of scalar quantities u, such as temperature or
More informationCHAPTER V DUAL SPACES
CHAPTER V DUAL SPACES DEFINITION Let (X, T ) be a (real) locally convex topological vector space. By the dual space X, or (X, T ), of X we mean the set of all continuous linear functionals on X. By the
More informationON APPROXIMATE DIFFERENTIABILITY OF THE MAXIMAL FUNCTION
ON APPROXIMATE DIFFERENTIABILITY OF THE MAXIMAL FUNCTION PIOTR HAJ LASZ, JAN MALÝ Dedicated to Professor Bogdan Bojarski Abstract. We prove that if f L 1 R n ) is approximately differentiable a.e., then
More informationTHEOREMS, ETC., FOR MATH 515
THEOREMS, ETC., FOR MATH 515 Proposition 1 (=comment on page 17). If A is an algebra, then any finite union or finite intersection of sets in A is also in A. Proposition 2 (=Proposition 1.1). For every
More informationUniversität des Saarlandes. Fachrichtung 6.1 Mathematik
Universität des Saarlandes U N I V E R S I T A S S A R A V I E N I S S Fachrichtung 6.1 Mathematik Preprint Nr. 225 Estimates of the second-order derivatives for solutions to the two-phase parabolic problem
More informationP(E t, Ω)dt, (2) 4t has an advantage with respect. to the compactly supported mollifiers, i.e., the function W (t)f satisfies a semigroup law:
Introduction Functions of bounded variation, usually denoted by BV, have had and have an important role in several problems of calculus of variations. The main features that make BV functions suitable
More informationFREMLIN TENSOR PRODUCTS OF CONCAVIFICATIONS OF BANACH LATTICES
FREMLIN TENSOR PRODUCTS OF CONCAVIFICATIONS OF BANACH LATTICES VLADIMIR G. TROITSKY AND OMID ZABETI Abstract. Suppose that E is a uniformly complete vector lattice and p 1,..., p n are positive reals.
More informationTHE FORM SUM AND THE FRIEDRICHS EXTENSION OF SCHRÖDINGER-TYPE OPERATORS ON RIEMANNIAN MANIFOLDS
THE FORM SUM AND THE FRIEDRICHS EXTENSION OF SCHRÖDINGER-TYPE OPERATORS ON RIEMANNIAN MANIFOLDS OGNJEN MILATOVIC Abstract. We consider H V = M +V, where (M, g) is a Riemannian manifold (not necessarily
More informationFunctional Analysis I
Functional Analysis I Course Notes by Stefan Richter Transcribed and Annotated by Gregory Zitelli Polar Decomposition Definition. An operator W B(H) is called a partial isometry if W x = X for all x (ker
More informationCalculus of Variations. Final Examination
Université Paris-Saclay M AMS and Optimization January 18th, 018 Calculus of Variations Final Examination Duration : 3h ; all kind of paper documents (notes, books...) are authorized. The total score of
More informationLUSIN PROPERTIES AND INTERPOLATION OF SOBOLEV SPACES. Fon-Che Liu Wei-Shyan Tai. 1. Introduction and preliminaries
Topological Methods in Nonlinear Analysis Journal of the Juliusz Schauder Center Volume 9, 997, 63 77 LUSIN PROPERTIES AND INTERPOLATION OF SOBOLEV SPACES Fon-Che Liu Wei-Shyan Tai. Introduction and preliminaries
More informationFinite-dimensional spaces. C n is the space of n-tuples x = (x 1,..., x n ) of complex numbers. It is a Hilbert space with the inner product
Chapter 4 Hilbert Spaces 4.1 Inner Product Spaces Inner Product Space. A complex vector space E is called an inner product space (or a pre-hilbert space, or a unitary space) if there is a mapping (, )
More informationChapter 2 Metric Spaces
Chapter 2 Metric Spaces The purpose of this chapter is to present a summary of some basic properties of metric and topological spaces that play an important role in the main body of the book. 2.1 Metrics
More information6 Classical dualities and reflexivity
6 Classical dualities and reflexivity 1. Classical dualities. Let (Ω, A, µ) be a measure space. We will describe the duals for the Banach spaces L p (Ω). First, notice that any f L p, 1 p, generates the
More informationLecture No 1 Introduction to Diffusion equations The heat equat
Lecture No 1 Introduction to Diffusion equations The heat equation Columbia University IAS summer program June, 2009 Outline of the lectures We will discuss some basic models of diffusion equations and
More informationAppendix A Functional Analysis
Appendix A Functional Analysis A.1 Metric Spaces, Banach Spaces, and Hilbert Spaces Definition A.1. Metric space. Let X be a set. A map d : X X R is called metric on X if for all x,y,z X it is i) d(x,y)
More informationStrongly nonlinear parabolic initial-boundary value problems in Orlicz spaces
2002-Fez conference on Partial Differential Equations, Electronic Journal of Differential Equations, Conference 09, 2002, pp 203 220. http://ejde.math.swt.edu or http://ejde.math.unt.edu ftp ejde.math.swt.edu
More informationHARMONIC ANALYSIS. Date:
HARMONIC ANALYSIS Contents. Introduction 2. Hardy-Littlewood maximal function 3. Approximation by convolution 4. Muckenhaupt weights 4.. Calderón-Zygmund decomposition 5. Fourier transform 6. BMO (bounded
More informationOn Smoothness of Suitable Weak Solutions to the Navier-Stokes Equations
On Smoothness of Suitable Weak Solutions to the Navier-Stokes Equations G. Seregin, V. Šverák Dedicated to Vsevolod Alexeevich Solonnikov Abstract We prove two sufficient conditions for local regularity
More informationFunctional Analysis. Franck Sueur Metric spaces Definitions Completeness Compactness Separability...
Functional Analysis Franck Sueur 2018-2019 Contents 1 Metric spaces 1 1.1 Definitions........................................ 1 1.2 Completeness...................................... 3 1.3 Compactness......................................
More informationA Product Property of Sobolev Spaces with Application to Elliptic Estimates
Rend. Sem. Mat. Univ. Padova Manoscritto in corso di stampa pervenuto il 23 luglio 2012 accettato l 1 ottobre 2012 A Product Property of Sobolev Spaces with Application to Elliptic Estimates by Henry C.
More informationi=1 α i. Given an m-times continuously
1 Fundamentals 1.1 Classification and characteristics Let Ω R d, d N, d 2, be an open set and α = (α 1,, α d ) T N d 0, N 0 := N {0}, a multiindex with α := d i=1 α i. Given an m-times continuously differentiable
More informationProblem Set 6: Solutions Math 201A: Fall a n x n,
Problem Set 6: Solutions Math 201A: Fall 2016 Problem 1. Is (x n ) n=0 a Schauder basis of C([0, 1])? No. If f(x) = a n x n, n=0 where the series converges uniformly on [0, 1], then f has a power series
More informationLORENTZ ESTIMATES FOR ASYMPTOTICALLY REGULAR FULLY NONLINEAR ELLIPTIC EQUATIONS
Electronic Journal of Differential Equations, Vol. 27 27), No. 2, pp. 3. ISSN: 72-669. URL: http://ejde.math.txstate.edu or http://ejde.math.unt.edu LORENTZ ESTIMATES FOR ASYMPTOTICALLY REGULAR FULLY NONLINEAR
More informationMATHS 730 FC Lecture Notes March 5, Introduction
1 INTRODUCTION MATHS 730 FC Lecture Notes March 5, 2014 1 Introduction Definition. If A, B are sets and there exists a bijection A B, they have the same cardinality, which we write as A, #A. If there exists
More informationFriedrich symmetric systems
viii CHAPTER 8 Friedrich symmetric systems In this chapter, we describe a theory due to Friedrich [13] for positive symmetric systems, which gives the existence and uniqueness of weak solutions of boundary
More informationWavelets and modular inequalities in variable L p spaces
Wavelets and modular inequalities in variable L p spaces Mitsuo Izuki July 14, 2007 Abstract The aim of this paper is to characterize variable L p spaces L p( ) (R n ) using wavelets with proper smoothness
More informationTHE HARDY LITTLEWOOD MAXIMAL FUNCTION OF A SOBOLEV FUNCTION. Juha Kinnunen. 1 f(y) dy, B(x, r) B(x,r)
Appeared in Israel J. Math. 00 (997), 7 24 THE HARDY LITTLEWOOD MAXIMAL FUNCTION OF A SOBOLEV FUNCTION Juha Kinnunen Abstract. We prove that the Hardy Littlewood maximal operator is bounded in the Sobolev
More informationAN INTRODUCTION TO GEOMETRIC MEASURE THEORY AND AN APPLICATION TO MINIMAL SURFACES ( DRAFT DOCUMENT) Academic Year 2016/17 Francesco Serra Cassano
AN INTRODUCTION TO GEOMETRIC MEASURE THEORY AND AN APPLICATION TO MINIMAL SURFACES ( DRAFT DOCUMENT) Academic Year 2016/17 Francesco Serra Cassano Contents I. Recalls and complements of measure theory.
More informationCompactness in Ginzburg-Landau energy by kinetic averaging
Compactness in Ginzburg-Landau energy by kinetic averaging Pierre-Emmanuel Jabin École Normale Supérieure de Paris AND Benoît Perthame École Normale Supérieure de Paris Abstract We consider a Ginzburg-Landau
More informationSTOKES PROBLEM WITH SEVERAL TYPES OF BOUNDARY CONDITIONS IN AN EXTERIOR DOMAIN
Electronic Journal of Differential Equations, Vol. 2013 2013, No. 196, pp. 1 28. ISSN: 1072-6691. URL: http://ejde.math.txstate.edu or http://ejde.math.unt.edu ftp ejde.math.txstate.edu STOKES PROBLEM
More informationApplied Analysis (APPM 5440): Final exam 1:30pm 4:00pm, Dec. 14, Closed books.
Applied Analysis APPM 44: Final exam 1:3pm 4:pm, Dec. 14, 29. Closed books. Problem 1: 2p Set I = [, 1]. Prove that there is a continuous function u on I such that 1 ux 1 x sin ut 2 dt = cosx, x I. Define
More informationFact Sheet Functional Analysis
Fact Sheet Functional Analysis Literature: Hackbusch, W.: Theorie und Numerik elliptischer Differentialgleichungen. Teubner, 986. Knabner, P., Angermann, L.: Numerik partieller Differentialgleichungen.
More informationNew estimates for the div-curl-grad operators and elliptic problems with L1-data in the whole space and in the half-space
New estimates for the div-curl-grad operators and elliptic problems with L1-data in the whole space and in the half-space Chérif Amrouche, Huy Hoang Nguyen To cite this version: Chérif Amrouche, Huy Hoang
More informationON BOUNDEDNESS OF MAXIMAL FUNCTIONS IN SOBOLEV SPACES
Annales Academiæ Scientiarum Fennicæ Mathematica Volumen 29, 2004, 167 176 ON BOUNDEDNESS OF MAXIMAL FUNCTIONS IN SOBOLEV SPACES Piotr Haj lasz and Jani Onninen Warsaw University, Institute of Mathematics
More informationSome lecture notes for Math 6050E: PDEs, Fall 2016
Some lecture notes for Math 65E: PDEs, Fall 216 Tianling Jin December 1, 216 1 Variational methods We discuss an example of the use of variational methods in obtaining existence of solutions. Theorem 1.1.
More informationBasic Properties of Metric and Normed Spaces
Basic Properties of Metric and Normed Spaces Computational and Metric Geometry Instructor: Yury Makarychev The second part of this course is about metric geometry. We will study metric spaces, low distortion
More informationAsymptotic behavior of infinity harmonic functions near an isolated singularity
Asymptotic behavior of infinity harmonic functions near an isolated singularity Ovidiu Savin, Changyou Wang, Yifeng Yu Abstract In this paper, we prove if n 2 x 0 is an isolated singularity of a nonegative
More informationJUHA KINNUNEN. Harmonic Analysis
JUHA KINNUNEN Harmonic Analysis Department of Mathematics and Systems Analysis, Aalto University 27 Contents Calderón-Zygmund decomposition. Dyadic subcubes of a cube.........................2 Dyadic cubes
More informationInequalities of Babuška-Aziz and Friedrichs-Velte for differential forms
Inequalities of Babuška-Aziz and Friedrichs-Velte for differential forms Martin Costabel Abstract. For sufficiently smooth bounded plane domains, the equivalence between the inequalities of Babuška Aziz
More informationINF-SUP CONDITION FOR OPERATOR EQUATIONS
INF-SUP CONDITION FOR OPERATOR EQUATIONS LONG CHEN We study the well-posedness of the operator equation (1) T u = f. where T is a linear and bounded operator between two linear vector spaces. We give equivalent
More informationCAPACITIES ON METRIC SPACES
[June 8, 2001] CAPACITIES ON METRIC SPACES V. GOL DSHTEIN AND M. TROYANOV Abstract. We discuss the potential theory related to the variational capacity and the Sobolev capacity on metric measure spaces.
More informationTHE ALTERNATIVE DUNFORD-PETTIS PROPERTY FOR SUBSPACES OF THE COMPACT OPERATORS
THE ALTERNATIVE DUNFORD-PETTIS PROPERTY FOR SUBSPACES OF THE COMPACT OPERATORS MARÍA D. ACOSTA AND ANTONIO M. PERALTA Abstract. A Banach space X has the alternative Dunford-Pettis property if for every
More informationA GAGLIARDO NIRENBERG INEQUALITY, WITH APPLICATION TO DUALITY-BASED A POSTERIORI ESTIMATION IN THE L 1 NORM
27 Kragujevac J. Math. 30 (2007 27 43. A GAGLIARDO NIRENBERG INEQUALITY, WITH APPLICATION TO DUALITY-BASED A POSTERIORI ESTIMATION IN THE L 1 NORM Endre Süli Oxford University Computing Laboratory, Wolfson
More informationFonctions on bounded variations in Hilbert spaces
Fonctions on bounded variations in ilbert spaces Newton Institute, March 31, 2010 Introduction We recall that a function u : R n R is said to be of bounded variation (BV) if there exists an n-dimensional
More informationTitle: Localized self-adjointness of Schrödinger-type operators on Riemannian manifolds. Proposed running head: Schrödinger-type operators on
Title: Localized self-adjointness of Schrödinger-type operators on Riemannian manifolds. Proposed running head: Schrödinger-type operators on manifolds. Author: Ognjen Milatovic Department Address: Department
More informationNONTRIVIAL SOLUTIONS TO INTEGRAL AND DIFFERENTIAL EQUATIONS
Fixed Point Theory, Volume 9, No. 1, 28, 3-16 http://www.math.ubbcluj.ro/ nodeacj/sfptcj.html NONTRIVIAL SOLUTIONS TO INTEGRAL AND DIFFERENTIAL EQUATIONS GIOVANNI ANELLO Department of Mathematics University
More informationNew York Journal of Mathematics. A Refinement of Ball s Theorem on Young Measures
New York Journal of Mathematics New York J. Math. 3 (1997) 48 53. A Refinement of Ball s Theorem on Young Measures Norbert Hungerbühler Abstract. For a sequence u j : R n R m generating the Young measure
More informationELLIPTIC EQUATIONS WITH MEASURE DATA IN ORLICZ SPACES
Electronic Journal of Differential Equations, Vol. 2008(2008), No. 76, pp. 1 10. ISSN: 1072-6691. URL: http://ejde.math.txstate.edu or http://ejde.math.unt.edu ftp ejde.math.txstate.edu (login: ftp) ELLIPTIC
More informationREPRESENTABLE BANACH SPACES AND UNIFORMLY GÂTEAUX-SMOOTH NORMS. Julien Frontisi
Serdica Math. J. 22 (1996), 33-38 REPRESENTABLE BANACH SPACES AND UNIFORMLY GÂTEAUX-SMOOTH NORMS Julien Frontisi Communicated by G. Godefroy Abstract. It is proved that a representable non-separable Banach
More informationTotal Variation Theory and Its Applications
Total Variation Theory and Its Applications 2nd UCC Annual Research Conference, Kingston, Jamaica Peter Ndajah University of the Commonwealth Caribbean, Kingston, Jamaica September 27, 2018 Peter Ndajah
More informationASYMPTOTIC BEHAVIOUR OF NONLINEAR ELLIPTIC SYSTEMS ON VARYING DOMAINS
ASYMPTOTIC BEHAVIOUR OF NONLINEAR ELLIPTIC SYSTEMS ON VARYING DOMAINS Juan CASADO DIAZ ( 1 ) Adriana GARRONI ( 2 ) Abstract We consider a monotone operator of the form Au = div(a(x, Du)), with R N and
More informationFolland: Real Analysis, Chapter 7 Sébastien Picard
Folland: Real Analysis, Chapter 7 Sébastien Picard Problem 7.2 Let µ be a Radon measure on X. a. Let N be the union of all open U X such that µ(u) =. Then N is open and µ(n) =. The complement of N is called
More informationEXISTENCE RESULTS FOR QUASILINEAR HEMIVARIATIONAL INEQUALITIES AT RESONANCE. Leszek Gasiński
DISCRETE AND CONTINUOUS Website: www.aimsciences.org DYNAMICAL SYSTEMS SUPPLEMENT 2007 pp. 409 418 EXISTENCE RESULTS FOR QUASILINEAR HEMIVARIATIONAL INEQUALITIES AT RESONANCE Leszek Gasiński Jagiellonian
More informationMath The Laplacian. 1 Green s Identities, Fundamental Solution
Math. 209 The Laplacian Green s Identities, Fundamental Solution Let be a bounded open set in R n, n 2, with smooth boundary. The fact that the boundary is smooth means that at each point x the external
More informationLecture 9 Metric spaces. The contraction fixed point theorem. The implicit function theorem. The existence of solutions to differenti. equations.
Lecture 9 Metric spaces. The contraction fixed point theorem. The implicit function theorem. The existence of solutions to differential equations. 1 Metric spaces 2 Completeness and completion. 3 The contraction
More informationTHEOREMS, ETC., FOR MATH 516
THEOREMS, ETC., FOR MATH 516 Results labeled Theorem Ea.b.c (or Proposition Ea.b.c, etc.) refer to Theorem c from section a.b of Evans book (Partial Differential Equations). Proposition 1 (=Proposition
More informationESTIMATES FOR ELLIPTIC HOMOGENIZATION PROBLEMS IN NONSMOOTH DOMAINS. Zhongwei Shen
W,p ESTIMATES FOR ELLIPTIC HOMOGENIZATION PROBLEMS IN NONSMOOTH DOMAINS Zhongwei Shen Abstract. Let L = div`a` x, > be a family of second order elliptic operators with real, symmetric coefficients on a
More informationRENORMALIZED SOLUTIONS ON QUASI OPEN SETS WITH NONHOMOGENEOUS BOUNDARY VALUES TONI HUKKANEN
RENORMALIZED SOLTIONS ON QASI OPEN SETS WITH NONHOMOGENEOS BONDARY VALES TONI HKKANEN Acknowledgements I wish to express my sincere gratitude to my advisor, Professor Tero Kilpeläinen, for the excellent
More informationRegularizations of Singular Integral Operators (joint work with C. Liaw)
1 Outline Regularizations of Singular Integral Operators (joint work with C. Liaw) Sergei Treil Department of Mathematics Brown University April 4, 2014 2 Outline 1 Examples of Calderón Zygmund operators
More informationThe Banach Tarski Paradox and Amenability Lecture 20: Invariant Mean implies Reiter s Property. 11 October 2012
The Banach Tarski Paradox and Amenability Lecture 20: Invariant Mean implies Reiter s Property 11 October 2012 Invariant means and amenability Definition Let be a locally compact group. An invariant mean
More information