Lecture 13. Problems with the standard Model

Transcription

1 Lecture 13 Problems with the standard Model

2 Problems with the standard model 1: The horizon problem 2: The flatness problem 3: The defect problem 4: The structural scale problem 5: The expansion question 6: The black hole problem

3 The horizon problem (also called the isotropy problem) How can the CMB has such a uniform temperature across the whole sky when different direction so the sky are not in causal contact? Solution 1: The universe was formed at a uniform temperature.

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6 The horizon problem (also called the isotropy problem) How can the CMB has such a uniform temperature across the whole sky when different direction so the sky are not in causal contact? Solution 1: The universe was formed at a uniform temperature. (unsatisfactory)

7 The flatness problem Why should k = 0 (as measured from the CMB) Perhaps space has to be flat curved three dimensional space simply is aphysical Remember, curvature = contraction expansion This implies that a perfect balance exists, why?

8 The defect problem When matter is first created in the earliest times of the universe (well before nucleosynthesis), why were no anomalies formed that we can detect? Particle physics predicts their existence rare, but non-zero Defects include monopoles, strings and branes

9 Defects Perhaps the physics of formation (from energy to mass) is poorly understood, and no anomalies formed (i.e. we don t understand particle physics at super high energies)

10 The structural problem The size and magnitude of the fluctuations in the CMB are extremely well matched to the structures we see today, but are much larger than the random fluctuations we would expect in the universe at an age of 350,000 years Do we have the age of the CMB wrong? Are the fluctuations not random

11 The expansion problem Why is the universe expanding in the first place? Is it simply the nature of space to expand?

12 The black hole problem If going back in time leads me to a universe that is getting denser and denser, at some poit the mass inside a certain volume but be sufficient to be a black hole. If the universe was once a black hole how did it get out? A) We are still in the black hole B) We have the picture wrong in the very early universe

13 Brain Break

14 Egyptians: Established the zodiacal signs (very ancient) Marked the new year by the heliacal rising of Sirius, which presaged the flooding of the Nile

15 But they probably understood precession This may have been the great secret of the Egyptian priests

16 Precession

17 Precession of the equinoxes Precession of the zodiac 23,000 year cycle The sun now rises where it once set

18 More speculative: Are the monuments of Egypt (the pyramids in particular) representations of the sky or even great calendars?

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26 1882

27 1920

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29 Angkor Wat

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34 Navigation by the stars Latitude: easy Longitude: hard need a clock

35 Piri Reis Map (1513)

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39 1532

40 1532 Today

41 The solution: Inflation Inflation solves these problems but creates a whole new set of problems. Inflation assumes that VERY early in the history of the universe, space underwent superluminal expansion: causing regions within casual contact to leave casual contact (normally forbidden by special relativity)

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44 Inflation it neatly solves the horizon problem But introduces several new problems 1) Superluminal expansion!!! 2) Why would this expansion even occur?

45 Problems with the standard model 1: The horizon problem 2: The flatness problem 3: The defect problem 4: The structural scale problem 5: The expansion question 6: The black hole problem

46 Inflation makes the universe so large that the local observable universe appears flat

47 Problems with the standard model 1: The horizon problem 2: The flatness problem 3: The defect problem 4: The structural scale problem 5: The expansion question 6: The black hole problem

48 Defects The defects that would have been created are rare and unusual. Because the space we can currently observe arises from a tiny original volume, the odds that it would contain a defect are vanishingly small Expected number of monopoles in the observable universe today < 1

49 Problems with the standard model 1: The horizon problem 2: The flatness problem 3: The defect problem 4: The structural scale problem 5: The expansion question 6: The black hole problem

50 The structural scale problem The size of the fluctuations seen at the time of recombination are too large by a factor of e 60 This is assumed to be the value of the amount of expansion that occurred during inflation. e 60 = 1.1 x = 100 million billion billion In about seconds!

51 Problems with the standard model 1: The horizon problem 2: The flatness problem 3: The defect problem 4: The structural scale problem 5: The expansion question 6: The black hole problem

52 Expansion The speed of expansion at the end of inflation is simply the speed of expansion at the start of our observable universe Inflation caused the universe to be expanding

53 Expansion The speed of expansion at the end of inflation is simply the speed of expansion at the start of our observable universe Inflation caused the universe to be expanding (but what caused inflation?)

54 Problems with the standard model 1: The horizon problem 2: The flatness problem 3: The defect problem 4: The structural scale problem 5: The expansion question 6: The black hole problem

55 The black hole problem Our equation for a black whole assumed that space was static and the only force acting on it was gravity expanding space has a different solution, and the expansion allows the material to get outside the event horizon

56 Problems with the standard model 1: The horizon problem 2: The flatness problem 3: The defect problem 4: The structural scale problem 5: The expansion question 6: The black hole problem

57 However. This only adds a new set of questions: Why did the universe expand like that, and why did it stop? (what is the inflaton field?) What was the universe like before inflation?