We would like to give a Lagrangian formulation of electrodynamics.
|
|
- Daniel Cook
- 5 years ago
- Views:
Transcription
1 Chapter 7 Lagrangian Formulation of Electrodynamics We would like to give a Lagrangian formulation of electrodynamics. Using Lagrangians to describe dynamics has a number of advantages It is a exceedingly compact notation of describing dynamics. Recall for example, that a symmetry of the Lagrangian generally leads to conservation law and this is one method of learning about what quantities are conserved. Also from the Lagrangian one can constrtuct the Hamiltonian and H is essential in doing quantum mechanics. In fact in Feynman path integral formulation of quantum mechanics, one can express q.m. using only the Lagrangian. In conventional Lagrangian analysis one sets up the action integral A = t 2 t 1 Ldt and the dynamics law arise from varyoing it:δa = 0 Now if we wish the laws of physics to be the same in any inertial frame, we need to have δa to be Poincare invariant and this will be accomplished if A is invariant under Poincare transformation: A = A; x µ = Λ µ αx α + a µ up to a time derivative in L (which does not contribute to the equation of motion), Let us first look at equations of motion for the point 51
2 charges. The form of A = t 2 t 1 Ldt does not look Lorentz invariant since dt = dx 0 /c is really the fourth component of a vector. As in the equations of motion, this suggest for Poincare inavriance we should use τ instead of t to write. Assume dτ = dτ A = τ2 τ 1 Ldτ; L = scalar (7.1) wher L L (for v/c << 1). Now we had that the Lorentz force depends on the 4-velocity u µ = dx µ (τ)/dτ and so we expect L to be linear in this. But we must form a scalar from this and the E.M. field. The only vector to dot this out is A µ, i.e., u µ A µ ; A µ = η µν A µ (7.2) Since the alternative involving F µν itself is: u µ u ν F µν = 0 (7.3) This we suggest L = a + bu µ A µ ; a, b = const. (7.4) and A = dτ(a + bu µ A µ ) (7.5). The a term involves and expanding for small v/c adτ = dt dτ dt a = dt c a (7.6) 2 adτ = adt(1 1 v 2 2 c ) (7.7) 2 Thus if we choose a = m (7.8) 52
3 This corresponds to a non-relativistic Lagrangian of L = m mv (7.9) which gives the cortrect kinetic energy. The constant m does not contribute to the equation of motion. Hence we have A = dtl (7.10) where and writing out L = m L = m + b(dxµ dt A µ) (7.11) + b(ca 0 + v i A i ) (7.12) where A 0 = φ. The Lagrange equation reads Recall d dt ( ) L v j x i ( ) L x j v i = 0 (7.13) A i = A i (x i (t), t), φ = φ(x i (t), t) (7.14) Hence we get or Hence d ( vj dt ( mc2 ) d dt ( mv j ) + b(v i Aj φ + ba j ) b( c x + A j vi i x ) = 0 (7.15) j + A i x i t d dt ( mv j ) + b(v i Aj v i A i φ ) + bc( 1 x i xj x + 1 j c v2 ) + bc φ x j bvi A i x j = 0 (7.16) A i t ) = 0 (7.17) 53
4 Now recall Hence we can write u µ = dxµ dτ = 1 (c, v i ) (7.18) d dt (muj ) = b c u µf jµ 2 (7.19) and finally since we get d dt = dτ dt d dτ = d dτ (7.20) m duj dτ = bu µf jµ (7.21) which is correct with the choice b = e c (7.22) Our Lagrangian is this L = m + e c dx µ dt A µ (7.23) which generates what about the last equation to get u 0 : m duj dτ = e c u µf jµ (7.24) m du0 dτ = e c u µf 0µ (7.25) we know that this is just a equation to get the relation between t and τ which can alternately gotten from integarting dτ = dt (7.26) Hence Eq.7.25 and Eq.7.26 gives us the full dynamics or alternately with Eq.7.17 with b = e/c does. 54
5 We can construct the Hamiltonian from Eq.7.23 in the usual fashion. Writing Then the canonical momentum is and the Hamiltonian is L = m p i = L v i = + ea 0 + e c v. A (7.27) mvi e + 1 c A i (7.28) v2 H = p. v L (7.29) or H = p. v e c v. A + m + eφ (7.30) c2 Let us assume π i = p i e c Ai (7.31) Then Eq.7.28 reads and π i = H = π i v i + m mvi (7.32) + eφ (7.33) c2 In the Hamiltonian we eliminate v i in terms of p i. So we first solve Eq.7.32 backward. Thus squaring gives and hence π 2 = m2 v 2 (7.34) v 2 = π 2 π 2 + m 2 (7.35) 55
6 or and so = mc π2 + m 2 (7.36) v i c = π (7.37) π2 + m 2 Inserting Eq.7.36, Eq.7.37 into H of Eq.7.30 gives H = π 2 c π2 + m 2 c + m 2 c 3 + eφ (7.38) 2 π2 + m 2 c2 or H = π 2 + m 2 c 4 + eφ; π = p e c A (7.39) which is the Hamiltonian for a charge in the presence of an e.m. field characterized by A and φ. The second term is just the electrostatic energy while the first term coincides with the magnetic contribution. Expanding for π << mc gives H = m + π2 + eφ +.. (7.40) 2m which aside from the rest energy m is the usual non-relativistic Hamiltonian. In general, the Hamiltonian represents the energy of a particle when one is in an inertial frame. Let us look at the case of a free particle A µ = 0; H = E = p 2 + m 2 c 4 (7.41) The monemtim is then given by Eq.7.28 for the free particle p = m v ; v i = dx i dt (7.42) 56
7 Eliminating p in terms of v in Eq.7.41 gives E = m 2 v 2 + m 2 c 4 = mc2 We can write Eq.7.42 and Eq.7.43 in terms of 4-vector momentum. define (7.43) p µ = ( E c, pi ) (7.44) Then we have and p i = m dxi dt = m dx i ; dτ = dt (7.45) dτ and so p 0 = mc dx 0 = m dτ (7.46) p µ = m dxµ dτ = muµ (7.47) Thus p µ is a Lorentz 4-vector, i.e., energy and momentum in special relativity form a 4-vector. Note that the parameter m is constant associated with the particle, i.e., it is an intrinsic property of the particle (just as charge is). One recall m = rest mass of particle (7.48) and from Eq energy in frame at rest with respect to particle is just E rest = m (7.49) If one goes to a moving frame Then p µ transforms as a 4-vector p µ = Λ µ αp α (7.50) 57
8 and so the energy increases,i.e., if p µ : (mc, 0) then E = p 0 c = Λ 0 0p 0 c + Λ 0 ip i c = γm = mc2 (7.51) which is just Eq It is not the mass that changes, but rather the energy that changes as one goes to the moving frame. Similarly for the frame with relative velocity v: p i = Λ i 0p 0 + Λ i jp j = Λ i 0p 0 = γ( vi c )mc = γmvi = just as in Eq Note p µ p µ = m2 v 2 1 v2 m2 c4 1 v2 a free particle is represented by a plane wave mvi (7.52) = m 2 and m is invariant. Note that in q.m. ψ = e i (p.r Et) (7.53) we can write this as ψ = e i (p ix i E c ct) = e i (p ix i +p 0 x 0) ; p µ = η µν p ν = ( p 0, p i ) (7.54) Hence ψ = e i pµxµ (7.55) If we go to a new inertial frame Then x µ = Λ µ αx α + a µ = x µ x α xα + a µ ; p µ = (Λ 1 ) α µ p α; p µ = xβ x µ p β (7.56) ψ e i p µ x µ = e i p β xβ x µ x µ x α x α x +p β β x µ a µ now use xβ x α = δ β α Hence ψ e i pαxα e iφ, φ = p β x β x µ aµ (7.57) 58
9 Thus ψ changes by just a phase at most which does not change the physical content of the wavefunction. Thus the conventional plane wave of q.m. generalizes to Lorentz covariant form. Let us now return to our charges interacting with the e.m. field. We have obtained a Lagrangian for the particle and its interaction with the e.m. field. To complete prescription we had Lagrangian for the e.m. field itself. To see how that might go we can rewrite our interaction between the charge and the field in a more covariant looking form. We had from Eq.7.23: and so L = m + e c dx µ dτ c A 2 µ (7.58) A = dtl = m dt + e c dt dxµ dτ c A 2 µ = A part + A int (7.59) where A int = e c dτu µ A µ (x i (t), t(τ)) (7.60) we can rewrite this as A int = e c d 4 xdτu µ (τ)a µ (x α )δ 4 (x α x α (τ)) (7.61) Recall we had j µ (x) = e dτu µ (τ)δ 4 (x x(τ)) (7.62) So we have A int = 1 c d 4 xl int = dt d 3 xl int (7.63) 59
10 where L int = 1 c jµ (x)a µ (x) = interaction Lagrangian density (7.64) Eqs.7.63,7.64 suggest what the form of the action should be for a field system, i.e., it should be the volume integral of the Lagrangian density: A = 1 c d 4 xl (7.65) we saw that d 4 x is a scalar and so if A is to be invariant, i.e., A = A (7.66) so that the equations of motion look the same in all frame, we require L int = scalar (7.67) This precisely what L int is (which gives the coupling of the e.m. field to the charges). Of course when we vary A we must get from the requirement that δa vanishes, the field eqns. for the fields. Let us first therefore investigate the general form Lagrange s eqns. will take for a field system. We assume in general there are a set of fields Φ A (x) = fields (7.68) and an action where A = t2 d 3 x dtl(x) (7.69) t 1 L(x) = L(φ A (x), µ (φ A (x)) (7.70) 60
11 f df t 1 t 2 X Figure 7.1: We assume that under variations of φ A δφ A (x) = arbitrary with boundary condition; δφ A 0(r ), δφ A (r, t i ) 0(t i t 1, t 2 ) (7.71) That the action is an extrema, i.e., δa = 0 (7.72) To vary A explicitly gives δa = t2 d 3 x dt[ L(x) δφ A + L(x) t 1 φ A ( µ φ A ) µδφ A ] (7.73) Now L(x) ( µ φ A ) µδφ A = µ ( L(x) ( µ φ A ) δφ A) x ( L(x) µ ( µ φ A ) )δφ A (7.74) The first term vanishes since d 3 x dt µ F µ = dt d 3 x.f + t2 d 3 1 x t 1 c F 0 dt (7.75) t and both terms vanish by our b.c. in Eq Thus δa = 1 c [ L(x) φ A µ L(x) ( µ φ A ) ] φ A (7.76) 61
12 and since δa = 0 for arbitrary δφ A = 0 we get L(x) φ A µ L(x) ( µ φ A ) = 0 (7.77) These are the Lagranages equations for the system. We wish now to choose L such that Eq.7.76 yields Maxwell equation ν F µν = 1 c jµ (7.78) F µν = µ A ν ν A µ (7.79) Eqs.7.78,7.79 are first order differential equations. Since Eq.7.76 contains single derivative, L can be at most first order in field derivative and linear in these derivatives and at most quadratic in the fields since Eqs.7.78,7.79 are linear. Thus L can be constructed from F µν, A µ, µ A ν, λ F µν (7.80) Finally L must be Poincare scalar, so all the indices must be dotted out. The possibilities are F µν F µν ; F µν A µ A ν ; F µν µ A ν ; A µ A µ (7.81) i.e., other possibities are either quadratic in derivative (e.g.,( λ F µν )( λ F µν ) )or cubic or higher (e.g., A λ µ A ν λ F µν ) Now the second possibility vanishes identically F µν A µ A ν 0 (7.82) and the last possibility can be written as 1 2 F µν ( µ A ν ν A µ ) F µν ( µ A ν + ν A µ ) (7.83) (The last term is 0) Hence there are only to possibilities are (we neglect A µ A µ as it is not gauge inavriant); L em = 1 4 F µν F µν 1 2 F µν ( µ A ν ν A µ ) (7.84) 62
13 where we have chosen the constants as we will see to correctly give Maxwell equations. The total part of the Lagrangian is then L = L em + L int = 1 4 F µν F µν 1 2 F µν ( µ A ν ν A µ ) + 1 c jµ A µ (7.85) Our set of fields for Eq.7.76 are then {φ A } = {F µν, A µ } (7.86) and so we get the equations and L F L µν λ ( λ F µν ) = 0 (7.87) L L µ A ν ( µ A ν ) = 0 (7.88) we first consider Eq.7.87 and note that L does not depend on λ F µν so that we have To take the derivative of L w.r.t F µν, i.e., L = 0 (7.89) F µν F µν = η µα η νβ F αβ (7.90) we take the derivative by first varying w.r.t F µν δ F L = 1 4 δf µν F µν F µν η µα η νβ δf αβ 1 2 δf µν ( µ A ν ν A µ ) (7.91) In the second term we can write since all indices are summed F µν η µα η νβ δf αβ = F αβ η αµ η βν δf µν = F µν δf µν (7.92) So that the the first two terms combine to give δ F L = 1 2 δf µν F µν 1 2 δf µν ( µ A ν ν A µ ) (7.93) 63
14 The derivative is L F µν = δ F L δf µν = 1 2 (F µν ( µ A ν ν A µ )) (7.94) and hence Eq.7.87 reads F µν = µ A ν ν A µ (7.95) which is correct. To calculate Eq.7.88, we need first and to get the second term we first vary: L A ν = 1 c jν (7.96) δ A L = 1 2 F µν (δ( µ A ν ) F µν (δ( ν A µ ) (7.97) Hence and putting into Eq.7.88 gives L ( µ A ν ) = F µν (7.98) 1 c jν + µ F µν = 0 (7.99) or µ F νµ = 1 c jν (7.100) which is correctly Eq We can now generalize to a system with an arbitrary number of charged particles. The action that characterizes the dynmaics is then A = dt a ( m a a(t) )+ 1 c d 4 xj µ (x)a µ + 1 c d 4 x[ 1 4 F µν F µν 1 2 F µν ( µ A ν ν A µ )] (7.101) where j µ = c a e a dτu µ a(τ)δ 4 (x x a (τ)) (7.102) 64
15 In general we know that Maxwell s theory is gauge invariant and a gauge transformation is given in 4-vector form by A µ A µ + µ Λ(x); F µν F µν F µν (7.103) It is clear from Eq that the term µ A ν ν A µ is gauge invariant since µ A ν ν A µ ( µ A ν + µ ν Λ) ( ν A µ + µ ν Λ) = µ A ν ν A µ (7.104) But what about the interaction term 1 c d 4 xj µ A µ 1 c d 4 xj µ A µ + 1 c d 4 xj µ µ Λ (7.105) The last term can be written as (2) = 1 c d 4 x µ (j µ Λ) 1 c d 4 x( µ j µ )Λ (7.106) (2) = 1 c d 3 xj(r, t) 0 Λ(r, t)] t=t 1 1 t=t 2 c d 4 x( µ j µ )Λ (7.107) We are free to choose Λ to be arbitrary at any interior point and vanish at end point. Then (2 ) = 1 c d 4 x( µ j µ )Λ (7.108) But µ j µ = 0 is conservation of charge. Hence 1 c d 4 xj µ A µ = gauge invariant (7.109) for any arbitrary gauge transformation for t 2 < t < t 1. Gauge invariance is thus a consequence of conservation of charge. 65
Lecture 16 March 29, 2010
Lecture 16 March 29, 2010 We know Maxwell s equations the Lorentz force. Why more theory? Newton = = Hamiltonian = Quantum Mechanics Elegance! Beauty! Gauge Fields = Non-Abelian Gauge Theory = Stard Model
More informationContinuity Equations and the Energy-Momentum Tensor
Physics 4 Lecture 8 Continuity Equations and the Energy-Momentum Tensor Lecture 8 Physics 4 Classical Mechanics II October 8th, 007 We have finished the definition of Lagrange density for a generic space-time
More informationDynamics of Relativistic Particles and EM Fields
October 7, 2008 1 1 J.D.Jackson, Classical Electrodynamics, 3rd Edition, Chapter 12 Lagrangian Hamiltonian for a Relativistic Charged Particle The equations of motion [ d p dt = e E + u ] c B de dt = e
More informationFYS 3120: Classical Mechanics and Electrodynamics
FYS 3120: Classical Mechanics and Electrodynamics Formula Collection Spring semester 2014 1 Analytical Mechanics The Lagrangian L = L(q, q, t), (1) is a function of the generalized coordinates q = {q i
More informationÜbungen zur Elektrodynamik (T3)
Arnold Sommerfeld Center Ludwig Maximilians Universität München Prof. Dr. Ivo Sachs SoSe 08 Übungen zur Elektrodynamik (T3) Lösungen zum Übungsblatt 7 Lorentz Force Calculate dx µ and ds explicitly in
More informationPhysics 411 Lecture 22. E&M and Sources. Lecture 22. Physics 411 Classical Mechanics II
Physics 411 Lecture 22 E&M and Sources Lecture 22 Physics 411 Classical Mechanics II October 24th, 2007 E&M is a good place to begin talking about sources, since we already know the answer from Maxwell
More informationThe Lorentz Force and Energy-Momentum for Off-Shell Electromagnetism
TAUP 1824-90 The Lorentz Force and Energy-Momentum for Off-Shell Electromagnetism M.C. Land 1 and L.P. Horwitz 2 School of Physics and Astronomy Raymond and Beverly Sackler Faculty of Exact Sciences Tel
More informationPhysics 214 Examples of four-vectors Winter 2017
Physics 214 Examples of four-vectors Winter 2017 1. The velocity four-vector The velocity four-vector of a particle is defined by: u µ = dxµ dτ = γc; γ v), 1) where dτ = γ 1 is the differential proper
More informationSolution to Problem Set 4
Solution to Problem Set 4 October 017 Pb 1. 0 pts. There are many ways of doing this problem but the easiest would be â α =â ˆD(α) 0 = â exp ( αâ α â ) 0 = â e α α/ e αâ 0 = α + α e α α/ e αâ 0 = α + α
More information2.3 Calculus of variations
2.3 Calculus of variations 2.3.1 Euler-Lagrange equation The action functional S[x(t)] = L(x, ẋ, t) dt (2.3.1) which maps a curve x(t) to a number, can be expanded in a Taylor series { S[x(t) + δx(t)]
More informationVector Fields. It is standard to define F µν = µ ϕ ν ν ϕ µ, so that the action may be written compactly as
Vector Fields The most general Poincaré-invariant local quadratic action for a vector field with no more than first derivatives on the fields (ensuring that classical evolution is determined based on the
More informationGeneral Relativity (j µ and T µν for point particles) van Nieuwenhuizen, Spring 2018
Consistency of conservation laws in SR and GR General Relativity j µ and for point particles van Nieuwenhuizen, Spring 2018 1 Introduction The Einstein equations for matter coupled to gravity read Einstein
More informationIntroduction to Covariant Formulation
Introduction to Covariant Formulation by Gerhard Kristensson April 1981 (typed and with additions June 2013) 1 y, z y, z S Event x v S x Figure 1: The two coordinate systems S and S. 1 Introduction and
More informationChapter 10 Operators of the scalar Klein Gordon field. from my book: Understanding Relativistic Quantum Field Theory.
Chapter 10 Operators of the scalar Klein Gordon field from my book: Understanding Relativistic Quantum Field Theory Hans de Vries November 11, 2008 2 Chapter Contents 10 Operators of the scalar Klein Gordon
More informationOverthrows a basic assumption of classical physics - that lengths and time intervals are absolute quantities, i.e., the same for all observes.
Relativistic Electrodynamics An inertial frame = coordinate system where Newton's 1st law of motion - the law of inertia - is true. An inertial frame moves with constant velocity with respect to any other
More informationLecture 4. Alexey Boyarsky. October 6, 2015
Lecture 4 Alexey Boyarsky October 6, 2015 1 Conservation laws and symmetries 1.1 Ignorable Coordinates During the motion of a mechanical system, the 2s quantities q i and q i, (i = 1, 2,..., s) which specify
More informationElectric and Magnetic Forces in Lagrangian and Hamiltonian Formalism
Electric and Magnetic Forces in Lagrangian and Hamiltonian Formalism Benjamin Hornberger 1/26/1 Phy 55, Classical Electrodynamics, Prof. Goldhaber Lecture notes from Oct. 26, 21 Lecture held by Prof. Weisberger
More informationWe begin our discussion of special relativity with a power point presentation, available on the website.
Special Relativity We begin our discussion of special relativity with a power point presentation, available on the website.. Spacetime From the power point presentation, you know that spacetime is a four
More informationQuantum Field Theory II
Quantum Field Theory II T. Nguyen PHY 391 Independent Study Term Paper Prof. S.G. Rajeev University of Rochester April 2, 218 1 Introduction The purpose of this independent study is to familiarize ourselves
More informationScalar Fields and Gauge
Physics 411 Lecture 23 Scalar Fields and Gauge Lecture 23 Physics 411 Classical Mechanics II October 26th, 2007 We will discuss the use of multiple fields to expand our notion of symmetries and conservation.
More informationRelativistic Mechanics
Physics 411 Lecture 9 Relativistic Mechanics Lecture 9 Physics 411 Classical Mechanics II September 17th, 2007 We have developed some tensor language to describe familiar physics we reviewed orbital motion
More informationLecture: Lorentz Invariant Dynamics
Chapter 5 Lecture: Lorentz Invariant Dynamics In the preceding chapter we introduced the Minkowski metric and covariance with respect to Lorentz transformations between inertial systems. This was shown
More informationWeek 1, solution to exercise 2
Week 1, solution to exercise 2 I. THE ACTION FOR CLASSICAL ELECTRODYNAMICS A. Maxwell s equations in relativistic form Maxwell s equations in vacuum and in natural units (c = 1) are, E=ρ, B t E=j (inhomogeneous),
More information(a p (t)e i p x +a (t)e ip x p
5/29/3 Lecture outline Reading: Zwiebach chapters and. Last time: quantize KG field, φ(t, x) = (a (t)e i x +a (t)e ip x V ). 2Ep H = ( ȧ ȧ(t)+ 2E 2 E pa a) = p > E p a a. P = a a. [a p,a k ] = δ p,k, [a
More informationQuantum Field Theory I Examination questions will be composed from those below and from questions in the textbook and previous exams
Quantum Field Theory I Examination questions will be composed from those below and from questions in the textbook and previous exams III. Quantization of constrained systems and Maxwell s theory 1. The
More information3 Quantization of the Dirac equation
3 Quantization of the Dirac equation 3.1 Identical particles As is well known, quantum mechanics implies that no measurement can be performed to distinguish particles in the same quantum state. Elementary
More informationRelativistic Dynamics
Chapter 4 Relativistic Dynamics The most important example of a relativistic particle moving in a potential is a charged particle, say an electron, moving in an electromagnetic field, which might be that
More information2.4 Parity transformation
2.4 Parity transformation An extremely simple group is one that has only two elements: {e, P }. Obviously, P 1 = P, so P 2 = e, with e represented by the unit n n matrix in an n- dimensional representation.
More informationQuantization of scalar fields
Quantization of scalar fields March 8, 06 We have introduced several distinct types of fields, with actions that give their field equations. These include scalar fields, S α ϕ α ϕ m ϕ d 4 x and complex
More informationPROBLEM SET 1 SOLUTIONS
MASSACHUSETTS INSTITUTE OF TECHNOLOGY Physics Department 8.323: Relativistic Quantum Field Theory I Prof.Alan Guth February 29, 2008 PROBLEM SET 1 SOLUTIONS Problem 1: The energy-momentum tensor for source-free
More informationRelativistic Quantum Mechanics
Physics 342 Lecture 34 Relativistic Quantum Mechanics Lecture 34 Physics 342 Quantum Mechanics I Wednesday, April 30th, 2008 We know that the Schrödinger equation logically replaces Newton s second law
More informationGENERAL RELATIVITY: THE FIELD THEORY APPROACH
CHAPTER 9 GENERAL RELATIVITY: THE FIELD THEORY APPROACH We move now to the modern approach to General Relativity: field theory. The chief advantage of this formulation is that it is simple and easy; the
More informationTHE QFT NOTES 5. Badis Ydri Department of Physics, Faculty of Sciences, Annaba University, Annaba, Algeria. December 9, 2011
THE QFT NOTES 5 Badis Ydri Department of Physics, Faculty of Sciences, Annaba University, Annaba, Algeria. December 9, 2011 Contents 1 The Electromagnetic Field 2 1.1 Covariant Formulation of Classical
More informationSpecial Relativity - QMII - Mechina
Special Relativity - QMII - Mechina 2016-17 Daniel Aloni Disclaimer This notes should not replace a course in special relativity, but should serve as a reminder. I tried to cover as many important topics
More informationPhysics on Curved Spaces 2
Physics on Curved Spaces 2 May 11, 2017 2 Based on: General Relativity M.P.Hobson, G. Efstahiou and A.N. Lasenby, Cambridge 2006 (Chapter 6 ) Gravity E. Poisson, C.M. Will, Cambridge 2014 Physics on Curved
More informationQuantum Electrodynamics Test
MSc in Quantum Fields and Fundamental Forces Quantum Electrodynamics Test Monday, 11th January 2010 Please answer all three questions. All questions are worth 20 marks. Use a separate booklet for each
More informationLinearized Gravity Return to Linearized Field Equations
Physics 411 Lecture 28 Linearized Gravity Lecture 28 Physics 411 Classical Mechanics II November 7th, 2007 We have seen, in disguised form, the equations of linearized gravity. Now we will pick a gauge
More informationMaxwell s equations. electric field charge density. current density
Maxwell s equations based on S-54 Our next task is to find a quantum field theory description of spin-1 particles, e.g. photons. Classical electrodynamics is governed by Maxwell s equations: electric field
More informationNewton s Second Law is Valid in Relativity for Proper Time
Newton s Second Law is Valid in Relativity for Proper Time Steven Kenneth Kauffmann Abstract In Newtonian particle dynamics, time is invariant under inertial transformations, and speed has no upper bound.
More informationWeek 1. 1 The relativistic point particle. 1.1 Classical dynamics. Reading material from the books. Zwiebach, Chapter 5 and chapter 11
Week 1 1 The relativistic point particle Reading material from the books Zwiebach, Chapter 5 and chapter 11 Polchinski, Chapter 1 Becker, Becker, Schwartz, Chapter 2 1.1 Classical dynamics The first thing
More information2 Feynman rules, decay widths and cross sections
2 Feynman rules, decay widths and cross sections 2.1 Feynman rules Normalization In non-relativistic quantum mechanics, wave functions of free particles are normalized so that there is one particle in
More information752 Final. April 16, Fadeev Popov Ghosts and Non-Abelian Gauge Fields. Tim Wendler BYU Physics and Astronomy. The standard model Lagrangian
752 Final April 16, 2010 Tim Wendler BYU Physics and Astronomy Fadeev Popov Ghosts and Non-Abelian Gauge Fields The standard model Lagrangian L SM = L Y M + L W D + L Y u + L H The rst term, the Yang Mills
More information221A Lecture Notes Electromagnetic Couplings
221A Lecture Notes Electromagnetic Couplings 1 Classical Mechanics The coupling of the electromagnetic field with a charged point particle of charge e is given by a term in the action (MKSA system) S int
More informationAs usual, these notes are intended for use by class participants only, and are not for circulation. Week 6: Lectures 11, 12
As usual, these notes are intended for use by class participants only, and are not for circulation Week 6: Lectures, The Dirac equation and algebra March 5, 0 The Lagrange density for the Dirac equation
More information3.3 Lagrangian and symmetries for a spin- 1 2 field
3.3 Lagrangian and symmetries for a spin- 1 2 field The Lagrangian for the free spin- 1 2 field is The corresponding Hamiltonian density is L = ψ(i/ µ m)ψ. (3.31) H = ψ( γ p + m)ψ. (3.32) The Lagrangian
More informationPhysics on Curved Spaces 2
Physics on Curved Spaces 2 November 29, 2017 2 Based on: General Relativity M.P.Hobson, G. Efstahiou and A.N. Lasenby, Cambridge 2006 (Chapter 6 ) Gravity E. Poisson, C.M. Will, Cambridge 2014 Physics
More informationContravariant and covariant vectors
Faculty of Engineering and Physical Sciences Department of Physics Module PHY08 Special Relativity Tensors You should have acquired familiarity with the following ideas and formulae in attempting the questions
More informationAttempts at relativistic QM
Attempts at relativistic QM based on S-1 A proper description of particle physics should incorporate both quantum mechanics and special relativity. However historically combining quantum mechanics and
More informationPhysics 582, Problem Set 1 Solutions
Physics 582, Problem Set 1 Solutions TAs: Hart Goldman and Ramanjit Sohal Fall 2018 1. THE DIRAC EQUATION [20 PTS] Consider a four-component fermion Ψ(x) in 3+1D, L[ Ψ, Ψ] = Ψ(i/ m)ψ, (1.1) where we use
More informationVectors in Special Relativity
Chapter 2 Vectors in Special Relativity 2.1 Four - vectors A four - vector is a quantity with four components which changes like spacetime coordinates under a coordinate transformation. We will write the
More informationConstruction of Field Theories
Physics 411 Lecture 24 Construction of Field Theories Lecture 24 Physics 411 Classical Mechanics II October 29th, 2007 We are beginning our final descent, and I ll take the opportunity to look at the freedom
More informationQuantum Field Theory Notes. Ryan D. Reece
Quantum Field Theory Notes Ryan D. Reece November 27, 2007 Chapter 1 Preliminaries 1.1 Overview of Special Relativity 1.1.1 Lorentz Boosts Searches in the later part 19th century for the coordinate transformation
More informationGeneral Relativity (225A) Fall 2013 Assignment 2 Solutions
University of California at San Diego Department of Physics Prof. John McGreevy General Relativity 5A) Fall 13 Assignment Solutions Posted October 3, 13 Due Monday, October 15, 13 1. Special relativity
More informationetc., etc. Consequently, the Euler Lagrange equations for the Φ and Φ fields may be written in a manifestly covariant form as L Φ = m 2 Φ, (S.
PHY 396 K. Solutions for problem set #3. Problem 1a: Let s start with the scalar fields Φx and Φ x. Similar to the EM covariant derivatives, the non-abelian covariant derivatives may be integrated by parts
More informationContinuous Symmetries and Conservation Laws. Noether s Theorem
As far as the laws of mathematics refer to reality, they are not certain; and as far as they are certain, they do not refer to reality. Albert Einstein (1879-1955) 3 Continuous Symmetries and Conservation
More informationSpecial classical solutions: Solitons
Special classical solutions: Solitons by Suresh Govindarajan, Department of Physics, IIT Madras September 25, 2014 The Lagrangian density for a single scalar field is given by L = 1 2 µφ µ φ Uφ), 1) where
More informationMaxwell s equations. based on S-54. electric field charge density. current density
Maxwell s equations based on S-54 Our next task is to find a quantum field theory description of spin-1 particles, e.g. photons. Classical electrodynamics is governed by Maxwell s equations: electric field
More informationGravitation: Special Relativity
An Introduction to General Relativity Center for Relativistic Astrophysics School of Physics Georgia Institute of Technology Notes based on textbook: Spacetime and Geometry by S.M. Carroll Spring 2013
More informationIntroduction to gauge theory
Introduction to gauge theory 2008 High energy lecture 1 장상현 연세대학교 September 24, 2008 장상현 ( 연세대학교 ) Introduction to gauge theory September 24, 2008 1 / 72 Table of Contents 1 Introduction 2 Dirac equation
More informationSpecial Relativity-General Discussion
Chapter 1 Special Relativity-General Discussion Let us consider a space-time event. By this we mean a physical occurence at some point in space at a given time. In order to characterize this event we introduce
More informationMechanics Physics 151
Mechanics Physics 151 Lecture 15 Special Relativity (Chapter 7) What We Did Last Time Defined Lorentz transformation Linear transformation of 4-vectors that conserve the length in Minkowski space Derived
More informationProperties of Traversable Wormholes in Spacetime
Properties of Traversable Wormholes in Spacetime Vincent Hui Department of Physics, The College of Wooster, Wooster, Ohio 44691, USA. (Dated: May 16, 2018) In this project, the Morris-Thorne metric of
More information8.821 F2008 Lecture 12: Boundary of AdS; Poincaré patch; wave equation in AdS
8.821 F2008 Lecture 12: Boundary of AdS; Poincaré patch; wave equation in AdS Lecturer: McGreevy Scribe: Francesco D Eramo October 16, 2008 Today: 1. the boundary of AdS 2. Poincaré patch 3. motivate boundary
More informationB(r) = µ 0a 2 J r 2ρ 2
28 S8 Covariant Electromagnetism: Problems Questions marked with an asterisk are more difficult.. Eliminate B instead of H from the standard Maxwell equations. Show that the effective source terms are
More informationLagrangian. µ = 0 0 E x E y E z 1 E x 0 B z B y 2 E y B z 0 B x 3 E z B y B x 0. field tensor. ν =
Lagrangian L = 1 4 F µνf µν j µ A µ where F µν = µ A ν ν A µ = F νµ. F µν = ν = 0 1 2 3 µ = 0 0 E x E y E z 1 E x 0 B z B y 2 E y B z 0 B x 3 E z B y B x 0 field tensor. Note that F µν = g µρ F ρσ g σν
More informationLecture 13 Notes, Electromagnetic Theory II Dr. Christopher S. Baird, faculty.uml.edu/cbaird University of Massachusetts Lowell
Lecture 13 Notes, Electromagnetic Theory II Dr. Christopher S. Baird, faculty.uml.edu/cbaird University of Massachusetts Lowell 1. Covariant Geometry - We would like to develop a mathematical framework
More informationVariational Principle and Einstein s equations
Chapter 15 Variational Principle and Einstein s equations 15.1 An useful formula There exists an useful equation relating g µν, g µν and g = det(g µν ) : g x α = ggµν g µν x α. (15.1) The proof is the
More informationMATH 423 January 2011
MATH 423 January 2011 Examiner: Prof. A.E. Faraggi, Extension 43774. Time allowed: Two and a half hours Full marks can be obtained for complete answers to FIVE questions. Only the best FIVE answers will
More informationClassical Field Theory
Classical Field Theory Asaf Pe er 1 January 12, 2016 We begin by discussing various aspects of classical fields. We will cover only the bare minimum ground necessary before turning to the quantum theory,
More informationMSci EXAMINATION. Date: XX th May, Time: 14:30-17:00
MSci EXAMINATION PHY-415 (MSci 4242 Relativistic Waves and Quantum Fields Time Allowed: 2 hours 30 minutes Date: XX th May, 2010 Time: 14:30-17:00 Instructions: Answer THREE QUESTIONS only. Each question
More informationOutline. Basic Principles. Extended Lagrange and Hamilton Formalism for Point Mechanics and Covariant Hamilton Field Theory
Outline Outline Covariant Hamiltonian Formulation of Gauge Theories J. 1 GSI Struckmeier1,, D. Vasak3, J. Kirsch3, H. 1 Basics:,, General Relativity 3 Global symmetry of a dynamical system Local symmetry
More informationScalar Electrodynamics. The principle of local gauge invariance. Lower-degree conservation
. Lower-degree conservation laws. Scalar Electrodynamics Let us now explore an introduction to the field theory called scalar electrodynamics, in which one considers a coupled system of Maxwell and charged
More informationThe Klein-Gordon equation
Lecture 8 The Klein-Gordon equation WS2010/11: Introduction to Nuclear and Particle Physics The bosons in field theory Bosons with spin 0 scalar (or pseudo-scalar) meson fields canonical field quantization
More informationSPECIAL RELATIVITY AND ELECTROMAGNETISM
SPECIAL RELATIVITY AND ELECTROMAGNETISM MATH 460, SECTION 500 The following problems (composed by Professor P.B. Yasskin) will lead you through the construction of the theory of electromagnetism in special
More informationPHY 396 K. Problem set #3. Due September 29, 2011.
PHY 396 K. Problem set #3. Due September 29, 2011. 1. Quantum mechanics of a fixed number of relativistic particles may be a useful approximation for some systems, but it s inconsistent as a complete theory.
More informationSymmetry and Duality FACETS Nemani Suryanarayana, IMSc
Symmetry and Duality FACETS 2018 Nemani Suryanarayana, IMSc What are symmetries and why are they important? Most useful concept in Physics. Best theoretical models of natural Standard Model & GTR are based
More informationChapter 3: Duality Toolbox
3.: GENEAL ASPECTS 3..: I/UV CONNECTION Chapter 3: Duality Toolbox MIT OpenCourseWare Lecture Notes Hong Liu, Fall 04 Lecture 8 As seen before, equipped with holographic principle, we can deduce N = 4
More informationQFT Perturbation Theory
QFT Perturbation Theory Ling-Fong Li (Institute) Slide_04 1 / 43 Interaction Theory As an illustration, take electromagnetic interaction. Lagrangian density is The combination L = ψ (x ) γ µ ( i µ ea µ
More informationLecture 5: Sept. 19, 2013 First Applications of Noether s Theorem. 1 Translation Invariance. Last Latexed: September 18, 2013 at 14:24 1
Last Latexed: September 18, 2013 at 14:24 1 Lecture 5: Sept. 19, 2013 First Applications of Noether s Theorem Copyright c 2005 by Joel A. Shapiro Now it is time to use the very powerful though abstract
More informationRelativistic Electrodynamics
Relativistic Electrodynamics Notes (I will try to update if typos are found) June 1, 2009 1 Dot products The Pythagorean theorem says that distances are given by With time as a fourth direction, we find
More informationPhysics 452 Lecture 33: A Particle in an E&M Field
Physics 452 Lecture 33: A Particle in an E&M Field J. Peatross In lectures 31 and 32, we considered the Klein-Gordon equation for a free particle. We would like to add a potential to the equation (since
More informationLecture 9: RR-sector and D-branes
Lecture 9: RR-sector and D-branes José D. Edelstein University of Santiago de Compostela STRING THEORY Santiago de Compostela, March 6, 2013 José D. Edelstein (USC) Lecture 9: RR-sector and D-branes 6-mar-2013
More informationbe stationary under variations in A, we obtain Maxwell s equations in the form ν J ν = 0. (7.5)
Chapter 7 A Synopsis of QED We will here sketch the outlines of quantum electrodynamics, the theory of electrons and photons, and indicate how a calculation of an important physical quantity can be carried
More informationNumber-Flux Vector and Stress-Energy Tensor
Massachusetts Institute of Technology Department of Physics Physics 8.962 Spring 2002 Number-Flux Vector and Stress-Energy Tensor c 2000, 2002 Edmund Bertschinger. All rights reserved. 1 Introduction These
More information8.821 String Theory Fall 2008
MIT OpenCourseWare http://ocw.mit.edu 8.81 String Theory Fall 008 For information about citing these materials or our Terms of Use, visit: http://ocw.mit.edu/terms. 8.81 F008 Lecture 1: Boundary of AdS;
More informationRelativistic Kinematics
Chapter 3 Relativistic Kinematics Recall that we briefly discussed Galilean boosts, transformation going from one inertial frame to another one, the first moving with an infinitesimal velocity δv with
More informationE & M Qualifier. January 11, To insure that the your work is graded correctly you MUST:
E & M Qualifier 1 January 11, 2017 To insure that the your work is graded correctly you MUST: 1. use only the blank answer paper provided, 2. use only the reference material supplied (Schaum s Guides),
More informationÜbungen zur Elektrodynamik (T3)
Arnold Sommerfeld Center Ludwig Maximilians Universität München Prof. Dr. Ivo Sachs SoSe 17 Übungen zur Elektrodynamik T3) Lösungen zum Übungsblatt 6 1 Lorentz Force The equations of motion for the trajectory
More informationLecturer: Bengt E W Nilsson
2009 05 07 Lecturer: Bengt E W Nilsson From the previous lecture: Example 3 Figure 1. Some x µ s will have ND or DN boundary condition half integer mode expansions! Recall also: Half integer mode expansions
More informationHamiltonian Field Theory
Hamiltonian Field Theory August 31, 016 1 Introduction So far we have treated classical field theory using Lagrangian and an action principle for Lagrangian. This approach is called Lagrangian field theory
More informationYang-Mills Gravity and Accelerated Cosmic Expansion* (Based on a Model with Generalized Gauge Symmetry)
review research Yang-Mills Gravity and Accelerated Cosmic Expansion* (Based on a Model with Generalized Gauge Symmetry) Jong-Ping Hsu Physics Department, Univ. of Massachusetts Dartmouth, North Dartmouth,
More informationSpecial Relativity-General Discussion
Chapter 1 Special Relativity-General Discussion Let us consider a spacetime event. By this we mean a physical occurence at some point in space at a given time. in order to characterize this event we introduce
More informationOutline 1. Introduction 1.1. Historical Overview 1.2. The Theory 2. The Relativistic String 2.1. Set Up 2.2. The Relativistic Point Particle 2.3. The
Classical String Theory Proseminar in Theoretical Physics David Reutter ETH Zürich April 15, 2013 Outline 1. Introduction 1.1. Historical Overview 1.2. The Theory 2. The Relativistic String 2.1. Set Up
More information4-Vector Notation. Chris Clark September 5, 2006
4-Vector Notation Chris Clark September 5, 2006 1 Lorentz Transformations We will assume that the reader is familiar with the Lorentz Transformations for a boost in the x direction x = γ(x vt) ȳ = y x
More informationClassical Physics. SpaceTime Algebra
Classical Physics with SpaceTime Algebra David Hestenes Arizona State University x x(τ ) x 0 Santalo 2016 Objectives of this talk To introduce SpaceTime Algebra (STA) as a unified, coordinate-free mathematical
More informationCovariant electrodynamics
Lecture 9 Covariant electrodynamics WS2010/11: Introduction to Nuclear and Particle Physics 1 Consider Lorentz transformations pseudo-orthogonal transformations in 4-dimentional vector space (Minkowski
More informationPhysics 217 FINAL EXAM SOLUTIONS Fall u(p,λ) by any method of your choosing.
Physics 27 FINAL EXAM SOLUTIONS Fall 206. The helicity spinor u(p, λ satisfies u(p,λu(p,λ = 2m. ( In parts (a and (b, you may assume that m 0. (a Evaluate u(p,λ by any method of your choosing. Using the
More informationClassical and Quantum Mechanics of a Charged Particle Moving in Electric and Magnetic Fields
Classical Mechanics Classical and Quantum Mechanics of a Charged Particle Moving in Electric and Magnetic Fields In this section I describe the Lagrangian and the Hamiltonian formulations of classical
More informationParticle Notes. Ryan D. Reece
Particle Notes Ryan D. Reece July 9, 2007 Chapter 1 Preliminaries 1.1 Overview of Special Relativity 1.1.1 Lorentz Boosts Searches in the later part 19th century for the coordinate transformation that
More informationPhysics 214 UCSD Lecture 7 Halzen & Martin Chapter 4
Physics 214 UCSD Lecture 7 Halzen & Martin Chapter 4 (Spinless) electron-muon scattering Cross section definition Decay rate definition treatment of identical particles symmetrizing crossing Electrodynamics
More information