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![Page 1: George E. A. Matsas Instituto de Física Teórica/ Unesp Search for low-energy semi-classical gravity effects.](https://reader035.fdocuments.us/reader035/viewer/2022070401/56649f175503460f94c2dcf9/html5/thumbnails/1.jpg)
George E. A. MatsasGeorge E. A. Matsas
Instituto de Física Teórica/ Instituto de Física Teórica/ UnespUnesp
Search for low-energy Search for low-energy semi-classical gravity semi-classical gravity
effectseffects
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Challenges of new physics in Challenges of new physics in spacespace
for quantum gravityfor quantum gravity
Is the big bang a true singularity?Is the big bang a true singularity? What is the physics of super-hot universe:What is the physics of super-hot universe: T> 10 T> 101919 GeV GeV? ? Is dark energy a (low-energy) quantum gravity effect? Is dark energy a (low-energy) quantum gravity effect? Do black holes Do black holes reallyreally evaporate? (transplanckian modes issue)evaporate? (transplanckian modes issue) What is the final stage of black hole evaporation? What is the final stage of black hole evaporation? Is there any black hole information paradox?Is there any black hole information paradox? Are there naked singularities and are they really “singular”?Are there naked singularities and are they really “singular”? Can quantum gravity fool the cosmic censor?Can quantum gravity fool the cosmic censor? ......
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What is Quantum Gravity?What is Quantum Gravity?
C. Rovelli, “Notes for a brief history of Quantum Gravity”, gr-qc/0006061
NOBODY NOWS
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Necessary condition: Quantum Gravity includes observables which depend simultaneously on c, h and G
(in CGS units).
Quantum gravity effect space
Complexity (# of parameters)
Energy
238
8
)/(101cM
MMPl
bhsun
2cM Pl
Semiclassical gravity regime
Full quantum gravity regime
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Semiclassical gravity regime
Full quantum gravity regime
Semiclassical gravitySemiclassical gravity(quantum field theory in curved spacetimes + (quantum field theory in curved spacetimes +
backreaction effects)backreaction effects)
Globally hiperbolic spacetimes
TG 8
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Stanford Linear Accelerator Center cortesy
Hawking effect Hawking effect (Nature 248(1974)30)(Nature 248(1974)30)
Semiclassical gravity regime
Full quantum gravity regime
238
8
)/(101cM
MMkT Pl
bhsunH
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Stanford Linear Accelerator Center cortesy
Unruh effect Unruh effect (Phys. Rev. D 14(1976)870)(Phys. Rev. D 14(1976)870)
251
2
)/(103cM
gakT PlU
D. Vanzella, GEAM, Phys.Rev.Lett. 87 (2001) 151301
Semiclassical gravity regime
Full quantum gravity regime
Elementary particle concept
Crispino, GEAM, Higuchi, Rev.Mod.Phys. 80(2008)787
enp 0
0)( nepv
0)( nepvii
enpvi 0)(
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Semiclassical gravity regime
Full quantum gravity regime
Unruh effect
Hawking effect
“Go slow to arrive the soonest”
KMMT bhsunH )/(106 8
KgaTU )/(104 20
Old physics on Earth helps new physics in Old physics on Earth helps new physics in spacespace
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Sonic holesSonic holes (Unruh, Phys. Rev. D 46(1981)1351)(Unruh, Phys. Rev. D 46(1981)1351)
Problem: Transplanckian modes
Solution(?): Is the spacetime like a fluid? Question: Do we loose Lorentz invariance at Planck scale?
Semiclassical gravity regime
Full quantum gravity regime
hydrodynamics
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Cosmic Censorship ConjectureCosmic Censorship Conjecture
Weak Cosmic Censorship ConjectureWeak Cosmic Censorship Conjecture
If one starts out with an initially non-singular asymptotically flat situation, any If one starts out with an initially non-singular asymptotically flat situation, any singularities which subsequently develop due to gravitational collapse will be singularities which subsequently develop due to gravitational collapse will be hidden from the view of an observer at infinity by the event horizon of a black hidden from the view of an observer at infinity by the event horizon of a black
hole hole
(Penrose, Nuovo Cimento 1969)(Penrose, Nuovo Cimento 1969)
unpredictable
Naked singularities are so imoral that there may exist cosmic censors to dress them all (but the big
bang) with event horizons.
Semiclassical gravity regime
Full quantum gravity regime
Particle physics
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ANTI-Cosmic Censorship ANTI-Cosmic Censorship ConjectureConjecture
ANTI-Cosmic Censorship ConjectureANTI-Cosmic Censorship Conjecture
Because quantum gravity should unveil the physics of naked singularities and recover the predictability of the Universe, there must exist anti-cosmic censors guarantying the existence of
naked-singularity quantum generation mechanisms
Made predictable by quantum mechanics
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tΣ=M R
Σ t
tim
e
(Choptuik, PRL 1993)
Naked singularity
SPECIAL initial conditions
Naked singularity Naked singularity fromfrom matter matter collapse?collapse?
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M = R×Σ t
Σ t
tim
e
GENERIC initial conditions
Naked singularity Naked singularity fromfrom matter matter collapse?collapse?
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Black Holes and Naked Black Holes and Naked SingularitiesSingularities
2222 / MJ+QM 2222 / MJ+QM
Question: Is it possible to overspin or overcharge a black hole stripping bare a
black hole to reveal its singularity?
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Throwing a Throwing a classicalclassical particle particle into an extreme black holeinto an extreme black hole
2222 / E)+(ML)+(J+q)+(QE)+(M
E , q , L
2222 / MJ+QM
(Wald, Ann. Phys. 74)
Gra
vit
ati
onal Pote
nti
al
r
)(max LV particle
particle
For related work with further developments see “Overcharging a black hole and cosmic
censorship”. (Hubeny, PRD 99)
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r
)(max LV
(G.E.A.M. & A.R.R. da Silva, Phys. Rev. Lett 2007)[comments also in Nature, 450, 147 (2007)]
particle
Gra
vit
ati
on
al Pote
nti
al
Overspinning a charged black Overspinning a charged black hole via quantum tunneling?hole via quantum tunneling?
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The backreaction issueThe backreaction issue
(Hod, PRL 2008)
(GEAM, Richartz, Saa, da Silva, Vanzella, submitted to publication)
(Richartz & Saa, PRD 2008)
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Quantum GravityQuantum Gravityfinal veredictumfinal veredictum
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Generalized second lawGeneralized second law
2222 / MJ+QM 2222 / MJ+QM
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Naked singularity/elementary particle Naked singularity/elementary particle conjectureconjecture
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This is time to reflect on how risky our bets towards Quantum Gravity should be