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Miami 2010, Ft. Lauderdale, Dec. 19, 2010 1/20 Niayesh Afshordi, Perimeter Institute/U-Waterloo...
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Transcript of Miami 2010, Ft. Lauderdale, Dec. 19, 2010 1/20 Niayesh Afshordi, Perimeter Institute/U-Waterloo...
![Page 1: Miami 2010, Ft. Lauderdale, Dec. 19, 2010 1/20 Niayesh Afshordi, Perimeter Institute/U-Waterloo Missing Baryons!! Gonzalez, Zaritsky, & Zabludoff 2007.](https://reader036.fdocuments.us/reader036/viewer/2022062518/56649de85503460f94ae1faf/html5/thumbnails/1.jpg)
Miami 2010, Ft. Lauderdale, Dec. 19, 2010 1/20Niayesh Afshordi, Perimeter Institute/U-Waterloo
Missing Baryons!!
Gonzalez, Zaritsky, & Zabludoff 2007 NA, Lin, Nagai, & Sanderson 2007
27% § 8% of baryons are neither in stars or gas!Recently confirmed by Atacama Cosmology Telescope & South Pole telescope
X-rays++ Sunyaev-Zel’dovich (WMAP3)
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Miami 2010, Ft. Lauderdale, Dec. 19, 2010 2/20Niayesh Afshordi, Perimeter Institute/U-Waterloo
Dark Energy, Black Hole Entropy, and the First Precision Measurement in
Quantum Gravity!
Niayesh Afshordi
![Page 3: Miami 2010, Ft. Lauderdale, Dec. 19, 2010 1/20 Niayesh Afshordi, Perimeter Institute/U-Waterloo Missing Baryons!! Gonzalez, Zaritsky, & Zabludoff 2007.](https://reader036.fdocuments.us/reader036/viewer/2022062518/56649de85503460f94ae1faf/html5/thumbnails/3.jpg)
Miami 2010, Ft. Lauderdale, Dec. 19, 2010 3/20Niayesh Afshordi, Perimeter Institute/U-Waterloo
Outline
• Motivation: Reviving Gravitational Aether– Horava-Lifshitz (Quantum) Gravity– Cosmological Constant Problem
• Black Hole/Dark Energy connection– Thermodynamic argument– Trans-Planckian Ansatz
• Observations, Puzzles and Problems• Conclusions
NA 2010, arXiv:1004.2901
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Miami 2010, Ft. Lauderdale, Dec. 19, 2010 4/20Niayesh Afshordi, Perimeter Institute/U-Waterloo
Reviving Aether I:Horava-Lifshitz Gravity
• Gravity is (power-counting) renormalizable if – frequency / wavelength-3 (! / k3); Horava 09
• Lorentz invariance is broken at high energies• Preferred frame behaves like Aether• Michaelson-Morely experiment++ Aether should
decouple from matter at low energies• At low energies:
General Relativitymean extrinsic curvature of spatial hypersurfaces
local aether expansion (Hubble) rate
Behaves as an incompressible fluid (NA 2009)
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Miami 2010, Ft. Lauderdale, Dec. 19, 2010 5/20Niayesh Afshordi, Perimeter Institute/U-Waterloo
Reviving Aether II: Cosmological Constant Problems
• Old Cosmological Constant Problem (Pauli 1920’s)
– |½vac| ¿ 1033 kg/m3 (Standard Model of Particle Physics)
• New Cosmological Constant Problem: Dark Energy
– ½vac = (7.1 § 0.9) £ 10-27 kg/m3
• Coincidence Problem –½vac ' 2.7 ½m,0
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Miami 2010, Ft. Lauderdale, Dec. 19, 2010 6/20Niayesh Afshordi, Perimeter Institute/U-Waterloo
Quantum Gravity vs. Aether
Old CC problemNew CC problem
Coincidence problem
(UV-complete ) Quantum Gravity
Incompressible Gravitational Aether
Miaralda-Escude 2010
Horava 2009; NA 2009, …
NA 2008Prescod-Weinstein, NA, & Balogh 2009NA 2010
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Miami 2010, Ft. Lauderdale, Dec. 19, 2010 7/20Niayesh Afshordi, Perimeter Institute/U-Waterloo
Outline
• Motivation: Reviving Gravitational Aether– Horava-Lifshitz (Quantum) Gravity– Cosmological Constant Problem
• Black Hole/Dark Energy connection– Thermodynamic argument– Trans-Planckian Ansatz
• Observations, Puzzles and Problems: • Conclusions
![Page 8: Miami 2010, Ft. Lauderdale, Dec. 19, 2010 1/20 Niayesh Afshordi, Perimeter Institute/U-Waterloo Missing Baryons!! Gonzalez, Zaritsky, & Zabludoff 2007.](https://reader036.fdocuments.us/reader036/viewer/2022062518/56649de85503460f94ae1faf/html5/thumbnails/8.jpg)
Miami 2010, Ft. Lauderdale, Dec. 19, 2010 8/20Niayesh Afshordi, Perimeter Institute/U-Waterloo
Return of the Cosmological Constant!
(M, DE )(M, DE )(M, DE )
Supernovae Ia (Wood-Vasey et al. 2007)redshift /velocity
Accelerating Universe (post 1998)
Decelerating Universe (pre 1998)Lo
g (
dis
tance
)
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Miami 2010, Ft. Lauderdale, Dec. 19, 2010 9/20Niayesh Afshordi, Perimeter Institute/U-Waterloo
How Black Holes lead to cosmic acceleration
• Gravitational Aether:
space
z~ 20, stellar black holes form
z~ 0.5, aether pressure dominates cosmic expansion
acceleration time
Gravitational aether is sourced at black hole horizons
Why should black holes source Aether?
z~ 1000, Aether is uniform
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Miami 2010, Ft. Lauderdale, Dec. 19, 2010 10/20Niayesh Afshordi, Perimeter Institute/U-Waterloo
Aether: a thermodynamic theory?
• Black Hole Thermodynamics:– Bardeen, Carter, & Hawking 1973; Bekenstein 1973
• Einstein’s gravity and 2nd law: – TdS = dQ G¹º = T¹º (Jacobson 1995)
– Newtonian gravity as an entropic force (Verlinde 2010)
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Miami 2010, Ft. Lauderdale, Dec. 19, 2010 11/20Niayesh Afshordi, Perimeter Institute/U-Waterloo
Back Hole Entropy and Dark Energy
!
Horizon Temperature ¿ Planck Energy = 1
• What if gravitational aether has a thermal pressure?
• Let’s consider QG corrections to BH thermal properties (c.f. entanglement entropy) : – Entropy:– Energy/Mass:– Volume:
• Pressure becomes:
• Could astrophysical Black Holes source Dark Energy?!• Cosmic Acceleration, first precision measurement in Quantum Gravity!
® = (-3.1 § 0.4) £ 10-3 [MBH/10 M¯]-3
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Miami 2010, Ft. Lauderdale, Dec. 19, 2010 12/20Niayesh Afshordi, Perimeter Institute/U-Waterloo
Outline
• Motivation: Reviving Gravitational Aether– Horava-Lifshitz (Quantum) Gravity– Cosmological Constant Problem
• Black Hole/Dark Energy connection– Thermodynamic argument– Trans-Planckian Ansatz
• Observations, Puzzles and Problems• Conclusions
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Miami 2010, Ft. Lauderdale, Dec. 19, 2010 13/20Niayesh Afshordi, Perimeter Institute/U-Waterloo
Aether pressure at large distances
Aether/Black Hole spacetime
• Aether (½ = 0) around a spherical Black Hole:
• Limits far from and close to the horizon:
r À 2m
r -2m ¿ 2m
C. Prescod-Weinstein
Prescod-Weinstein, NA, & Balogh 2009
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Miami 2010, Ft. Lauderdale, Dec. 19, 2010 14/20Niayesh Afshordi, Perimeter Institute/U-Waterloo
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Miami 2010, Ft. Lauderdale, Dec. 19, 2010 15/20Niayesh Afshordi, Perimeter Institute/U-Waterloo
Stellar BH’s and cosmic acceleration
• The same integration constant describes solution close to and far from the BH “horizon”
UV-IR coupling• Maximum redshift: 1/(-32¼p0m2)• Assuming this to be = Planck Energy/Hawking Temp.
p0 = -1/(256 ¼2m3) = - observed ½DE for m = 73 M¯ !!!!
Formation of stellar Black Holes can trigger late-time cosmic acceleration
Cosmic acceleration: first concrete signature of quantum gravity!
Trans-Planckian ansatz quantum gravity near BH horizon
Prescod-Weinstein, NA, & Balogh 2009
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Miami 2010, Ft. Lauderdale, Dec. 19, 2010 16/20Niayesh Afshordi, Perimeter Institute/U-Waterloo
Outline
• Motivation: Reviving Gravitational Aether– Horava-Lifshitz (Quantum) Gravity– Cosmological Constant Problem
• Black Hole/Dark Energy connection– Thermodynamic argument– Trans-Planckian Ansatz
• Observations, Puzzles and Problems • Conclusions
![Page 17: Miami 2010, Ft. Lauderdale, Dec. 19, 2010 1/20 Niayesh Afshordi, Perimeter Institute/U-Waterloo Missing Baryons!! Gonzalez, Zaritsky, & Zabludoff 2007.](https://reader036.fdocuments.us/reader036/viewer/2022062518/56649de85503460f94ae1faf/html5/thumbnails/17.jpg)
Miami 2010, Ft. Lauderdale, Dec. 19, 2010 17/20Niayesh Afshordi, Perimeter Institute/U-Waterloo
Multiple BH’s and Effective Dark Energy
• multiple black holes:log m* = hlog mimass weighted
• As super-massive BH’s grow, the effective ½DE / m*
-3 decreases• Using a model for
formation of stars/SMBH’s
mea
n BH
mas
s (m
*)
WMAP5+BAO+SN
Prescod-Weinstein, NA, & Balogh 2009
2(ln P + Á) = 0
∆
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Miami 2010, Ft. Lauderdale, Dec. 19, 2010 18/20Niayesh Afshordi, Perimeter Institute/U-Waterloo
Joint Dark Energy Missions (WFIRST, LSST, EUCLID)
• Probe Dark Energy history with incredible precision over the next decade
confirm/rule out aether predictions
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Miami 2010, Ft. Lauderdale, Dec. 19, 2010 19/20Niayesh Afshordi, Perimeter Institute/U-Waterloo
Problems and Puzzles
• Formation of a Black Hole with Aether• Fundamental Theory and/or Action• Cosmological Structure Formation/Evolution• Coupling of Aether to Matter• Predictions for DE need formation history of
Astrophysical Black Hole: • Star Formation history• Initial Mass Function• AGN accretion history
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Miami 2010, Ft. Lauderdale, Dec. 19, 2010 20/20Niayesh Afshordi, Perimeter Institute/U-Waterloo
Conclusions
• Revival of Gravitational Aether has lead to novel solutions to the problems of Qunatum Gravity and Cosmological Constant
• Quantum Gravity Corrections to thermodynamics of astrophysical black holes can source Dark Energy– Observable connection between history of astrophysical BH’s and
DE evolution– Only (falsifiable) Dark Energy model without fine-tuning (to my
knowledge)! – First precision measurement in Quantum Gravity ?!
• Many questions remain: BH collapse, cosmological structure formation, Action, coupling to matter …FIN!
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Miami 2010, Ft. Lauderdale, Dec. 19, 2010 21/20Niayesh Afshordi, Perimeter Institute/U-Waterloo
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Miami 2010, Ft. Lauderdale, Dec. 19, 2010 22/20Niayesh Afshordi, Perimeter Institute/U-Waterloo
Late-time Acceleration scenario
• g00 around the black hole (m ¿ r ¿ H-1) looks like de-Sitter space, so slow-moving particles (i.e. stars/galaxies) accelerate away from the center
• As this happens around every BH, the coarse-grained universe should look like ¤ + matter with ½¤= -p0
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Miami 2010, Ft. Lauderdale, Dec. 19, 2010 23/20Niayesh Afshordi, Perimeter Institute/U-Waterloo
“But to claim that dark energy represents a profound mystery, is, in our opinion, nonsense. “Dark energy” is just a catch name for the observed acceleration of the universe, which is a phenomenon well described by currently accepted theories, and predicted by these theories, whose intensity is determined by a fundamental constant, now being measured. The measure of the acceleration only determines the value of a constant that was not previously measured. We have only discovered that a constant that so far (strangely) appeared to be vanishing, in fact is not vanishing. Our universe is full of mystery, but there is no mystery here.”
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Miami 2010, Ft. Lauderdale, Dec. 19, 2010 24/20Niayesh Afshordi, Perimeter Institute/U-Waterloo
Thanks to Marcelo Gleiser!
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Miami 2010, Ft. Lauderdale, Dec. 19, 2010 25/20Niayesh Afshordi, Perimeter Institute/U-Waterloo
Cosmological Constant and Technical Naturalness
Thanks to Marcelo Gleiser!
• A technically natural effective theory is insensitive to the cut-off• e.g. Newton’s laws, Standard Model (except for Higgs)• A theory that is not technically natural requires fine-tuning• A small (or zero) cosmological constant IS NOT technically natural
momentum
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Miami 2010, Ft. Lauderdale, Dec. 19, 2010 26/20Niayesh Afshordi, Perimeter Institute/U-Waterloo
Landscape/Multiverse “solution” to the CC problem
• All the possible choices of CC are realized in the multiverse, and we happen to live in the regions that are habitable
• “Critics claim that many of these theories lack empirical testability, and without hard physical evidence are unfalsifiable; outside the methodology of scientific investigation to confirm or disprove.” wikipedia
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Miami 2010, Ft. Lauderdale, Dec. 19, 2010 27/20Niayesh Afshordi, Perimeter Institute/U-Waterloo
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Miami 2010, Ft. Lauderdale, Dec. 19, 2010 28/20Niayesh Afshordi, Perimeter Institute/U-Waterloo
Gravitational Aether: (NA 2008)
solves the old cosmological constant problem
• The metric is now blind to vacuum energy:
• In order to satisfy the Bianchi identity:
• Further assume incompressible fluid/aether:
Motivation: Tests of gravity severely constrain new deg’s of freedom+ Horava-Lifshitz gravity
NA 2008
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Miami 2010, Ft. Lauderdale, Dec. 19, 2010 29/20Niayesh Afshordi, Perimeter Institute/U-Waterloo
Cosmology with Gravitational Aether
• Friedmann equation (NA 2008):
i.e., effective G depends on the Eq. of state.• Radiation vs. Matter era:• BBN (4He abundance) (Cyburt, Fields, Olive, & Skillman 2005)
(but 7Li prefers lower values)
• Ly-®+WMAP3 (Seljak, Slosar, McDonald 2006):
p/½ for matter
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Miami 2010, Ft. Lauderdale, Dec. 19, 2010 30/20Niayesh Afshordi, Perimeter Institute/U-Waterloo
How does aether affect tests of gravity?
• If:– Aether tracks matter– Internal pressure is negligible
Aether is indistinguishable from GR• But:– Cosmological Tests: BBN (He, Li), CMB, Ly-®– Aether is irrotational (?) e.g. gravitomagnetic effect due
to earth rotation can test it (Gravity Probe B, LAGEOS) – Self-gravitating objects with relativistic pressure (e.g.
neutron stars, supernovae) will be sensitive to aetherNA 2008; Aslanbeigi ,et al., in preparation
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Miami 2010, Ft. Lauderdale, Dec. 19, 2010 31/20Niayesh Afshordi, Perimeter Institute/U-Waterloo
Example of model predictions:Ly-® forest + WMAP5
GR
Aether
WMAP5
WMAP5+Ly-®
Aether is preferred to GR
G. Robbers
NA, Foster, Kohri, & Robbers, in preparation
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Miami 2010, Ft. Lauderdale, Dec. 19, 2010 32/20Niayesh Afshordi, Perimeter Institute/U-Waterloo
The Real BBN Constraints
General Relativity
Gravitational Aether
7Li prefers Aether to GR4He prefers GR to Aether
NA, Foster, Kohri, & Robbers, in preparation
baryon to photon ratio