Transcript No Slide Title

LCDM: Beyond the Standard Model
Rocky Kolb, University of Chicago
Venice
March 2007
Precision cosmology
Radiation:
0.005%
Chemical Elements:
(other than H & He) 0.025%



Neutrinos:
0.47%
Stars:
0.5%
LCDM
Free H
& He:
4%
Cold Dark Matter:
25%
+ inflationary perturbations
+ baryo/lepto genesis
Dark Energy (L):
70%
LCDM: reality or substitute for it?
The construction of a model … consists of snatching from the
enormous and complex mass of facts called reality a few simple,
easily managed key points which, when put together in some
cunning way, becomes for certain purposes a substitute for reality
itself.
Evsey Domar
Essays on the Theory of Economic Growth
It hardly matters to me whether he [Copernicus] claims that Earth
moves or that it is immobile, so long as we get an absolutely exact
knowledge of the movements of the stars and the periods of their
movements, so long as both are reduced to altogether exact
calculation.
Gemma Frisius
16th century Dutch astronomer
Standard cosmological model*
• Radiation
• Bright baryons
• Neutrinos
• Dark baryons
• Baryo/leptogenesis
• Inflation
• Hypotheses?
• Dark matter
• Saving the appearances?
• Dark energy
• Epicycles?
* Do we want one? The goal is not a standard one, but the correct one!
Radiation:
0.005%
Chemical Elements:
(other than H & He) 0.025%



Neutrinos:
0.47%
It’s OK in practice, but…
LCDM
How does it work in theory?
Stars:
0.5%
Free H
& He:
4%
Cold Dark Matter:
25%
+ inflationary perturbations
+ baryo/lepto genesis
Dark Energy (L):
70%
Epicycle I – Dark Energy
What is the nature of dark energy
“In questions like this,
truth is only to be had by
laying together many
variations of error.”
-- Virginia Woolf
A Room of Ones Own
High-z SNe are fainter than expected in the Einstein-deSitter model
confusing astronomical notation
related to supernova brightness
Einstein-de Sitter:
spatially flat
matter-dominated model
(maximum theoretical bliss)
Astier et al. (2006)
SNLS
LCDM
supernova redshift z
The case for L:
1) Hubble diagram
2) subtraction
3) age of the universe
4) structure formation
Subtraction
Wi  rirC
dynamics
rC  3H02 8pG
lensing
x-ray gas
simulations
cmb
power
spectrum
WTOTAL = 1 (CMB)
WM = 0.3
1 - 0.3 = 0.7
WTOTAL - WM = WL
How do we “know” there is dark energy?
• Assume model cosmology:
– Einstein equation + symmetry  Friedmann equation: H(z)
– Energy (and pressure) content: matter, radiation, Lambda 
– Input or integrate over cosmological parameters: H0, WB, etc.
• Calculate H(z)
• Calculate observables: dL(z) , dA( z ), …
• Compare to observations
• Model cosmology fits with L, but not without
All evidence for dark energy is indirect: observed expansion
history is not as calculated from the Einstein-de Sitter model
(homogeneous, matter-dominated, spatially flat model w/o L)
Evolution of H (in z or t) is a key quantity
Many observables based on H(z)
•
Luminosity distance
Flux = (Luminosity / 4p dL2)
•
Angular diameter distance
a = Physical size / dA
•
Volume (number counts)
N / V -1(z)
•
Age of the universe
•
Distances
Take sides!
•
Can’t hide from the data – LCDM too good to ignore
– SNIa
– Subtraction: 1.0 - 0.3 = 0.7 H(z) not given by
– Age
Einstein–de Sitter
– Large-scale structure
– …
G00  8p G T00(matter)
•
Dark energy, rL (modify right-hand side of Einstein equations)
1. Constant (“just” Einstein’s cosmological constant L)
2. Not constant (dynamics driven by scalar field: M ~ 10-33 eV)
•
Gravity (modify left-hand side of Einstein equations)
3. Beyond Einstein (non-GR: branes, etc.)
4. (Just) Einstein (GR: back reaction of inhomogeneities)
Tools for the right-hand side
scalar fields
(quintessence)
anthropic principle
(the landscape)
Modifying the left-hand side
• Braneworld modifies Friedmann equation
Binetruy, Deffayet, Langlois
• Gravitational force law modified at large distance
Five-dimensional at cosmic distances
• Tired gravitons
Deffayet, Dvali
& Gabadadze
Gregory, Rubakov & Sibiryakov;
Dvali, Gabadadze & Porrati
Gravitons metastable - leak into bulk
• Gravity repulsive at distance R  Gpc
Csaki, Erlich, Hollowood & Terning
• n = 1 KK graviton mode very light, m  (Gpc)-1
Kogan, Mouslopoulos,
Papazoglou, Ross & Santiago
• Einstein & Hilbert got it wrong
S = 16p G )
-1
d
4
x -g  R -  R )
4
• Backreaction of inhomogeneities
Carroll, Duvvuri, Turner, Trodden
Räsänen; Kolb, Matarrese, Notari & Riotto;
Notari; Kolb, Matarrese & Riotto
Acceleration from inhomogeneities
• Most conservative approach — nothing new
– no new fields (like 10-33 eV mass scalars)
– no extra long-range forces
– no modification of general relativity
– no modification of gravity at large distances
– no Lorentz violation
– no extra dimensions, bulks, branes, etc.
– no anthropic/landscape/faith-based reasoning
• Magnitude?: calculable from observables related to r r
• Why now?: acceleration triggered by era of non-linear structure
Acceleration from inhomogeneities
Homogeneous model
Inhomogeneous model
rh
ri  x )
a  Vh
a  Vi
3
h
H h = ah ah
3
i
H i = ai ai
r h = r i  x )  H h = Hi ?
We think not!
Epicycle II – Dark matter
What is dark matter?
“In questions like this, truth is only to be had
by laying together many variations of error.”
-- Virginia Woolf
A Room of Ones Own
WM ~ 0.04
dynamics
lensing
x-ray gas
simulations
cmb
power
spectrum
WB ~ 0.04
QSO
1937-1009
WMAP: WBh = 0.0224  0.0009
2
Tytler
Burles et al.
Dark Matter?
• Modified Newtonian dynamics (MOND)
MOND Takes a Bullet
Dark Matter?
• Modified Newtonian dynamics (MOND)
• Planets
• Dwarf
Size challenged
stars
stars
brown red white
• Black holes
• Beyond the standard model (WIMP)
Dark Matter?
• neutrinos
(hot dark matter)
WMAP + LSS
Dark Matter?
• neutrinos
(hot dark matter)
• sterile neutrinos, gravitinos
• LSP (neutralino, axino, …)
(warm dark matter)
(cold dark matter)
• LKP (lightest Kaluza-Klein particle)
• axions, axion clusters
• solitons (Q-balls; B-balls; Odd-balls, Screw-balls….)
• supermassive wimpzillas
Mass range
Interaction strength range
10-6 eV (10 -40 g) axions
10-8 M (10 25 g) axion clusters
Noninteracting: wimpzillas
Strongly interacting: B balls
Disturbing the Vacuum
Particle creation in an external electric field
e+
e+
e-
E
e-
Particle creation if energy gained in acceleration over a
Compton wavelength exceeds the particle’s rest-mass
Expanding Universe
Particle Creation
Arnowit, Birrell, Bunch, Davies, Deser, Ford, Fulling, Grib, Hu, Kofman, Lukash,
Mostepanenko, Page, Parker, Starobinski, Unruh, Vilenkin, Wald, Zel’dovich,…
It’s not a bug, it’s a feature!
first application:
density perturbations from inflation
gravitational waves from inflation
(Guth & Pi; Starobinski; Bardeen, Steinhardt, & Turner; Hawking; Rubakov;
Fabbi & Pollack; Allen)
new application:
dark matter
(Chung, Kolb, & Riotto; Kuzmin & Tkachev)
• require (super)massive particle “X”
• stable (or at least long lived)
Wimpzilla Characteristics:
• supermassive: 109 - 1019 GeV (~ 1012 GeV ?)
• abundance may depend only on mass
• abundance may be independent of interactions
– sterile?
– electrically charged?
– strong interactions?
– weak interactions?
•
unstable (lifetime > age of the universe)?
– UHE cosmic rays?
WIMP
or
WIMPZILLA
The nature of dark matter is a complex
natural phenomenon.
The neutralino is a simple, elegant,
compelling explanation.
“For every complex natural phenomenon
there is a simple, elegant, compelling,
wrong explanation.”
- Tommy Gold
LCDM: Beyond the Standard Model
(OR NOT!)
Rocky Kolb, University of Chicago
Venice
March 2007