Physics Letters B 797 (2019) 134881
Contents lists available at ScienceDirect
Physics Letters B
www.elsevier.com/locate/physletb
Modifications of the Page Curve from correlations within Hawking
radiation
Mishkat Al Alvi
a
, Mahbub Majumdar
b
, Md. Abdul Matin
c,1
, Moinul Hossain Rahat
d,∗
,
Avik Roy
e
a
Department of Physics and Astronomy, University of Minnesota, Duluth, MN 55812, USA
b
BRAC University, 66 Mohakhali, Dhaka 1212, Bangladesh
c
Bangladesh University of Engineering & Technology, Dhaka 1000, Bangladesh
d
Institute for Fundamental Theory, Department of Physics, University of Florida, Gainesville, FL 32611, USA
e
Center for Particles and Fields, Department of Physics, University of Texas at Austin, Austin, TX 78712, USA
a r t i c l e i n f o a b s t r a c t
Article history:
Received
19 August 2019
Accepted
20 August 2019
Available
online 22 August 2019
Editor:
M. Cveti
ˇ
c
Keywords:
Black
hole information paradox
Toy
model black hole
Qubit
model black hole
Quantum
correlations
Small
correction
We investigate quantum correlations between successive steps of black hole evaporation and investigate
whether they might resolve the black hole information paradox. ‘Small’ corrections in various models
were shown to be unable to restore unitarity. We study a toy qubit model of evaporation that allows
small quantum correlations between successive steps and reaffirm previous results. Then, we relax the
‘smallness’ condition and find a nontrivial upper and lower bound on the entanglement entropy change
during the evaporation process. This gives a quantitative measure of the size of the correction needed to
restore unitarity. We find that these entanglement entropy bounds lead to a significant deviation from
the expected Page curve.
© 2019 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license
(http://creativecommons.org/licenses/by/4.0/). Funded by SCOAP
3
.
1. Introduction
In 1972 Bekenstein audaciously associated a thermodynamic
entropy to black holes that was proportional to the horizon area
[1,2]. This picture was elaborated in [3–5], and a complete descrip-
tion
of classical black hole mechanics was presented in [5,6].
The conflict between classical gravity that asserted that black
holes don’t emit radiation, and the thermodynamic picture
whereby
they have a temperature, was resolved by Hawking in
1975 [7]. Using what are now standard techniques in curved space
quantum field theory, Hawking showed that a black hole radiates
as a black body with a temperature of
κ
2π
.
Hawking suggested a heuristic picture whereby pair produc-
tion
occurred around the horizon. One particle fell into the black
hole and another particle – the Hawking radiation – escaped to
asymptotia. The picture was given a concrete realization in terms
of tunneling by Parikh and Wilczek [8].
*
Corresponding author.
E-mail
addresses: alvi0016@d.umn.edu (M.A. Alvi), where.is.mahbub@gmail.com,
majumdar@bracu.ac.bd (M. Majumdar), mrahat@ufl.edu (M.H. Rahat),
aroy@utexas.edu (A. Roy).
1
Deceased.
However, this produced a new paradox. The ingoing and outgo-
ing
Hawking radiation from pair production would be entangled.
Thus, as the black hole evaporated, the entanglement entropy of
the outgoing radiation would steadily increase. The emitted Hawk-
ing
radiation at the end of the evaporation would then be entan-
gled
with “nothing.” Thus a black hole that began in a pure state
would end in a mixed state violating unitarity. This is the black
hole information paradox.
Suppose
it were possible to transfer the entanglement between
the outgoing radiation and radiation/matter inside the black hole,
to the outgoing radiation that came out late. Then all of the in-
formation
in the black hole could be carried out by late time
Hawking radiation and the final state would be a pure state – a
pure state of early outgoing radiation entangled with late outgoing
radiation.
It
was believed that one mechanism to realize this picture are
‘small’ correlations between the Hawking quanta. Many ‘small’ ef-
fects
might conceivably, collectively add up and allow for all of the
information to come out [9]. Using strong subadditivity, Mathur
showed that in a simple model of Hawking pairs being Bell pairs,
that small correlations were unable to decrease the entanglement
entropy enough to preserve unitarity [10]. Later, Mathur showed
that small correlations between consecutive, local, Hawking pair
https://doi.org/10.1016/j.physletb.2019.134881
0370-2693/
© 2019 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/). Funded by
SCOAP
3
.