J. Goodman – May 2003 Quarknet Symposium May 2003 Neutrinos, Dark Matter and the Cosmological Constant The Dark Side of the Universe Jordan Goodman University of Maryland

J. Goodman – May 2003 Outline Why do we care about neutrinos? Why do we think there is dark matter? Could some of it be neutrinos? The search for neutrino mass – Solar Neutrinos –Super-K –SNO –Kamland The accelerating Universe - Dark Energy –SCP –WMAP

J. Goodman – May 2003 Seeing Big Picture

J. Goodman – May 2003 Why do we think there is dark matter? Isn’t obvious that most of the matter in the Universe is in Stars? Spiral Galaxy

J. Goodman – May 2003 Why do we think there is dark matter? In a gravitationally bound system out past most of the mass V ~ 1/r 1/2 We can look at the rotation curves of other galaxies –They should drop off But they don’t!

J. Goodman – May 2003 Why do we think there is dark matter? There must be a large amount of unseen matter in the halo of galaxies –Maybe 20 times more than in the stars! –Our galaxy looks 30 kpc across but recent data shows that it looks like it’s 200 kpc across

J. Goodman – May 2003 Measuring the energy in the Universe We can measure the mass of clusters of galaxies with gravitational lensing These measurements give  mass ~0.3 We also know (from the primordial deuterium abundance) that only a small fraction is nucleons  nucleons < ~0.04 Gravitational lensing

J. Goodman – May 2003 What is this ghostly matter? Could it be neutrinos? How much neutrino mass would it take? –Proton mass is 938 MeV –Electron mass is 511 KeV –Neutrino mass of 2eV would solve the galaxy rotation problem – 20eV would close the Universe Theories say it can’t be all neutrinos –They have difficulty forming the kinds of structure observed. The structures they create are too large and form too late in the history of the universe

J. Goodman – May 2003 Super-Kamiokande

J. Goodman – May 2003 Super-Kamiokande

J. Goodman – May 2003 Cherenkov Radiation Boat moves through water faster than wave speed. Bow wave (wake)

J. Goodman – May 2003 Cherenkov Radiation Faster than wave speed Slower than wave speed

J. Goodman – May 2003 Cherenkov Radiation Aircraft moves through air faster than speed of sound. Sonic boom

J. Goodman – May 2003 Cherenkov Radiation When a charged particle moves through transparent media faster than speed of light in that media. Cherenkov radiation Cone of light

J. Goodman – May 2003 Cherenkov Radiation

J. Goodman – May 2003 Hubble Law

J. Goodman – May 2003 The expanding Universe The Universe is expanding Everything is moving away from everything Hubble’s law says the faster things are moving away the further they are away

J. Goodman – May 2003 The expanding Universe

J. Goodman – May 2003 Supernova Cosmology Project Set out to directly measure the deceleration of the Universe Measure distance vs brightness of a standard candle (type Ia Supernova) The Universe seems to be accelerating! Doesn’t fit Hubble Law (at 99% c.l.)

J. Goodman – May 2003 The expanding Universe

J. Goodman – May 2003 Energy Density in the Universe    may be made up of 2 parts a mass term and a “dark energy”  term (Cosmological Constant)    mass  energy Einstein invented  to keep the Universe static He later rejected it when he found out about Hubble expansion He called it his “biggest blunder”  m   

J. Goodman – May 2003 The Cosmological Constant

J. Goodman – May 2003 What is the “Shape” of Space? Closed Universe   >1 – C < 2  R Open Universe   <1 –Circumference (C) of a circle of radius R is C > 2  R Flat Universe   =1 – C = 2  R – Euclidean space

J. Goodman – May 2003 Results of SN Cosmology Project The Universe is accelerating The data require a positive value of  “Cosmological Constant” If    =1 then they find    ~ 0.7 ± 0.1

J. Goodman – May 2003 Accelerating Universe

J. Goodman – May 2003 Accelerating Universe

J. Goodman – May 2003 Measuring the energy in the Universe Studying the Cosmic Microwave radiation looks back at the radiation from 400,000 years after the “Big Bang”. This gives a measure of  0

J. Goodman – May 2003 Recent Results  0 =1  nucleon

J. Goodman – May 2003 WMAP -2003

J. Goodman – May 2003 WMAP

J. Goodman – May 2003 WMAP Results Universe is 13.7 billion years old with a margin of error of close to 1% Content of the Universe: 4% Atoms, 23% Cold Dark Matter, 73% Dark energy. Fast moving neutrinos do not play any major role in the evolution of structure in the universe. Expansion rate (Hubble constant) value: H o = 71 km/sec/Mpc (with a margin of error of about 5%) New evidence for Inflation (in polarized signal)

J. Goodman – May 2003 What does all the data say? Three pieces of data come together in one region    ~ 0.73  m ~ 0.27 (uncertainty  ~0.04) Universe is expanding & won’t collapse Only ~1/6 of the dark matter is ordinary matter (atoms) A previously unknown and unseen “dark energy” pervades all of space and is causing it to expand and accelerate

J. Goodman – May 2003 What do we know about “Dark Energy” It emits no light It acts like a large negative pressure P x ~ -  x It is approximately homogenous –At least it doesn’t cluster like matter Calculations of this pressure from first principles fail miserably – assuming it’s vacuum energy you predict a value of   ~ Bottom line – we know very little!

J. Goodman – May 2003 Conclusion  tota l = 1.02 ± 0.02 –The Universe is flat! The Universe is : ~1/2% Stars ~1/2% Neutrinos ~27% Dark Matter (only 4% is ordinary matter) ~73% Dark Energy We can see ~1/2% We can measure ~1/2% We can see the effect of ~27% (but don’t know what most of it is) And we are pretty much clueless about the other 3/4 of the Universe There is still a lot of Physics to learn!