First up today, the final Thursday of the conference, is Pedro Alevino with "Dark matter and dark energy: a review and prospects"
9.05 He is not a nuclear physicist - he's a cosmologist.
9.11 Hubble expansion implies an age of the universe of 14Gyr. Completely wrong of course - Genesis tells us it's only around 6,000 yrs old. I've seen the dinosaur footprints next to the human footprints.
9.13 Need an accelerating universe to give an age of universe greater than 10Gyr. This is puzzling to me - from my cosmology course I distinctly remembering solving the Friedmann-Robertson-Walker equations and getting a universe age of 13Gyr without any dark energy. Hmmmm...
9.14 And now the FRW equations and EoS of the universe are flashed up. We're introduced to omegas:
Omega_m - density of matter/critical density of matter
Omega_e - density of dark energy/critical density of matter
9.16 Critical density: smaller - expand forever, greater - collapses at some point. This is without dark energy.
9.17 Dark energy has already been assumed to exist. Evidence to follow...
9.20 Primordial nucleosynthesis, when T < 0.1MeV. From nucleosynthesis, we can derive that 5% of matter density of universe is baryonic.
9.24 Cosmic Microwave Background is shown. Most perfect black body spectrum known. Not totally perfect though, there are observed temperature fluctuations due to density fluctuations in the plasma of the early universe.
9.25 Size of fluctuations consistent with flat universe.
9.26 These fluctuations are responsible for large scale structure formation - we can see their echo in the distribution of galaxies.
9.27 I get the feeling that the speaker is going for a shock and awe approach to the talk. Cosmologists do simulations with more particles than there are people on Earth!
9.29 Here comes the Type Ia SN evidence. He skips over the fact that the data appears consistent with no dark energy as well as dark energy.
9.31 Dark matter! Evidence: rotation curves of galaxies. He mentions changing gravity, but this doesn't work in explaining galaxy cluster collisions (e.g. the Bullet cluster). I have been to talks by Modified Gravity people claiming that it can.
9.36 The next slide loses me, partly because I missed the definition of the 'w' parameter which tells us about the dark energy EoS. 9.37 More long equations. Shock and awe.
9.38 Not natural to have w = constant, apparently. Indeed, it's illegal in 13 states in the US.
9.39 What the ?&$%? I wouldn't want to look at that slide on hallucenogenics. I'm stuggling with just coffee.
9.40 I have absolutely no idea what these domain wall networks are. But they can provide dark energy.
9.41 Relativistic and non-relativistic colored splotches are shown. They both look the same. Nevertheless one is ruled out.
9.42 Unified dark matter and dark energy! What are we going to call this unholy union?
9.45 The Planck satellite is going to constrain some of this stuff by measuring the CMB to unprecedented accuracy.
9.46 Summary: everything is known, except for what is dark matter and dark energy?
9.47 I'm waiting for the promised connection to nuclear physics in any useful way for this audience.
9.50 Questions. Modifying gravity is asked about. Its is more complicated, but it can be made to explain observations - this is a little different to what was said earlier.
9.52 Carlos asks about the black hole contribution to dark matter. The black hole mas in the universe is rather uncertain.
9.54 Some English dude asks about the Type Ia supernovae data - that the data, by eye, appears to be consistent with no-dark energy as well as dark energy. He agrees, but statistically, when combined with other data, it favors dark energy. So its no good on its own, apparently.
9.56 Unbelievable - the same English dude has sneaked a second question in. He asks about the reason for the historical preference for dark matter rather than MOND. Why has, overwhelmingly, so much more effort has been devoted to dark matter than modifying gravity? Is it philosophical? The answer refers to modern evidence, which rather misses the point.
9.58 The English guy has finally shut up, and the talk ends.
9.05 He is not a nuclear physicist - he's a cosmologist.
9.06 The beginning of dark energy: Einstein's famous 'greatest mistake'- the cosmological constant introduced into his gravitational field equations to give a static universe. By doing this he missed the opportunity to theoretically predict the expanding universe discovered by Hubble in 1929 from redshifted spectral lines from galaxies. Einstein really was a bit dim, wasn't he?
9.11 Hubble expansion implies an age of the universe of 14Gyr. Completely wrong of course - Genesis tells us it's only around 6,000 yrs old. I've seen the dinosaur footprints next to the human footprints.
9.13 Need an accelerating universe to give an age of universe greater than 10Gyr. This is puzzling to me - from my cosmology course I distinctly remembering solving the Friedmann-Robertson-Walker equations and getting a universe age of 13Gyr without any dark energy. Hmmmm...
9.14 And now the FRW equations and EoS of the universe are flashed up. We're introduced to omegas:
Omega_m - density of matter/critical density of matter
Omega_e - density of dark energy/critical density of matter
9.16 Critical density: smaller - expand forever, greater - collapses at some point. This is without dark energy.
9.17 Dark energy has already been assumed to exist. Evidence to follow...
9.20 Primordial nucleosynthesis, when T < 0.1MeV. From nucleosynthesis, we can derive that 5% of matter density of universe is baryonic.
9.24 Cosmic Microwave Background is shown. Most perfect black body spectrum known. Not totally perfect though, there are observed temperature fluctuations due to density fluctuations in the plasma of the early universe.
9.25 Size of fluctuations consistent with flat universe.
9.26 These fluctuations are responsible for large scale structure formation - we can see their echo in the distribution of galaxies.
9.27 I get the feeling that the speaker is going for a shock and awe approach to the talk. Cosmologists do simulations with more particles than there are people on Earth!
9.29 Here comes the Type Ia SN evidence. He skips over the fact that the data appears consistent with no dark energy as well as dark energy.
9.31 Dark matter! Evidence: rotation curves of galaxies. He mentions changing gravity, but this doesn't work in explaining galaxy cluster collisions (e.g. the Bullet cluster). I have been to talks by Modified Gravity people claiming that it can.
9.36 The next slide loses me, partly because I missed the definition of the 'w' parameter which tells us about the dark energy EoS. 9.37 More long equations. Shock and awe.
9.38 Not natural to have w = constant, apparently. Indeed, it's illegal in 13 states in the US.
9.39 What the ?&$%? I wouldn't want to look at that slide on hallucenogenics. I'm stuggling with just coffee.
9.40 I have absolutely no idea what these domain wall networks are. But they can provide dark energy.
9.41 Relativistic and non-relativistic colored splotches are shown. They both look the same. Nevertheless one is ruled out.
9.42 Unified dark matter and dark energy! What are we going to call this unholy union?
9.45 The Planck satellite is going to constrain some of this stuff by measuring the CMB to unprecedented accuracy.
9.46 Summary: everything is known, except for what is dark matter and dark energy?
9.47 I'm waiting for the promised connection to nuclear physics in any useful way for this audience.
9.50 Questions. Modifying gravity is asked about. Its is more complicated, but it can be made to explain observations - this is a little different to what was said earlier.
9.52 Carlos asks about the black hole contribution to dark matter. The black hole mas in the universe is rather uncertain.
9.54 Some English dude asks about the Type Ia supernovae data - that the data, by eye, appears to be consistent with no-dark energy as well as dark energy. He agrees, but statistically, when combined with other data, it favors dark energy. So its no good on its own, apparently.
9.56 Unbelievable - the same English dude has sneaked a second question in. He asks about the reason for the historical preference for dark matter rather than MOND. Why has, overwhelmingly, so much more effort has been devoted to dark matter than modifying gravity? Is it philosophical? The answer refers to modern evidence, which rather misses the point.
9.58 The English guy has finally shut up, and the talk ends.
No comments:
Post a Comment
Post a comment