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

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? ......

What is Quantum Gravity?What is Quantum Gravity?

C. Rovelli, “Notes for a brief history of Quantum Gravity”, gr-qc/0006061

NOBODY NOWS

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

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

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

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)(

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

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

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

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

tΣ=M R

Σ t

tim

e

(Choptuik, PRL 1993)

Naked singularity

SPECIAL initial conditions

Naked singularity Naked singularity fromfrom matter matter collapse?collapse?

M = R×Σ t

Σ t

tim

e

GENERIC initial conditions

Naked singularity Naked singularity fromfrom matter matter collapse?collapse?

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?

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)

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?

The backreaction issueThe backreaction issue

(Hod, PRL 2008)

(GEAM, Richartz, Saa, da Silva, Vanzella, submitted to publication)

(Richartz & Saa, PRD 2008)

Quantum GravityQuantum Gravityfinal veredictumfinal veredictum

Generalized second lawGeneralized second law

2222 / MJ+QM 2222 / MJ+QM

Naked singularity/elementary particle Naked singularity/elementary particle conjectureconjecture

This is time to reflect on how risky our bets towards Quantum Gravity should be