A Potential Astrophysical Test of Quantum Gravity

A Potential Astrophysical Test of Quantum Gravity

Ue-Li Pen CITA

November 12, 2013

Overview

I First pulsar orbiting black discovered in 2013!

I Hawking Information problem

I Fuzzballs

I Pulsar lensing

Magnetar PSR J1745-2900

(credit: MPIfR/Ralph Eatough) mysterious discovery in 2013, orbiting galactic center black hole. Rafikov-Lai (2006): precision GR test?

Black Hole Information

Hawking (1974): black holes radiate: T = hc/k_Br_s ∼ µK. High entropy:

number of photons emitted S /kB ∼ 10⁷⁷. Very slow: one photon of λ ∼ rs ∼ km each λ/c ∼ms. (1981): information loss? Evaporation is a Schwinger mechanism, does not depend on inside of black hole.

Dilemma

I No Hair: all black holes look identical after a short time (hour?)

I radiation only depends on outside of BH

I emitted radiation does not depend on formation history

I leads to microscopic time irreversibility of physics!

I breakdown of causality/unitarity?

I An initial pure state evolves into mixed state after a Page time (half the mass is lost).

Entropy solution

I string theory to the rescue!

I Strominger-Vafa (1996): counting of microstates

I unitarity saved?

I Stringy counting not possible in classical limit: what happens with Hawking’s argument?

Fuzzballs

Samir Mathur+ (2002+): solutions to Hawking problem must be either non-local or hairy.

Orders of orders of magnitude

I Saha, partition function: ^P(n_P(n¹⁾

0) = ^g_g¹

0exp



−_k^∆E

BT



I probability to observe in substantially non-schwarzschild state:

I ∆E ∼ mc²

I ∆E

kBT ∼ 10⁷⁷

I S1 ∼ k_Blog g1& 10⁷⁷

I no-hair may be a great mis-estimate, off by 10⁷⁷ orders of magnitude!

Fuzzballs

I round black holes have minimum surface, are most unlikely!

I constructive stringy solutions of some eigenstates: no horizon for no entropy

I classical Black Holes are superpositions of “naked”

microstates

I evades Hawking’s argument: no scharzschild background

I multipole deviation from GR ∼ (r_S/r )^{l +2}

Landscape

I Firewall: aging of BH, destruction of observer

I remnants (Cornucopions)

I loops

I loss of unitarity/causality

I scientific test?

Lens

(credit: wikipedia) multiple imaging of pulsars: Boyle+ (2011+), Pen+ (2011+): interference of lensed images. Measure space-time metric to ∼ mm at Einstein radius.

Lensing Prospects

I ideal setup: pulsar orbiting BH at ∼ 10, 000r_S

I inclination similar to Einstein radius ∼ 1^o

I two main images form double slit interferometer (Young) near conjunction

I quantum lens: expect image decoherence ∼ 10⁻⁶rS ∼ cm

I order unity effect in scintillation pattern

New surveys

11 pulsar-neutron star binaries, 1 pulsar-BH binary known. New surveys (e.g. SKA, CHIME+) will increase number 10-fold.

Conclusions

I Astrophysical test of quantum gravity?

I Promising future if high inclination BH-PSR binaries are discovered

I large cylinder telescopes (e.g. CHIME+) for searching

I scientific test for some scenarios of quantum gravity:

coherence of pulsar scintillation