Physics Letters B 781 (2018) 232–237
Contents lists available at ScienceDirect
Physics Letters B
www.elsevier.com/locate/physletb
Holographic entanglement entropy and entanglement thermodynamics
of ‘black’ non-susy D3 brane
Aranya Bhattacharya
a,b
, Shibaji Roy
a,b,∗
a
Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Calcutta 700064, India
b
Homi Bhabha National Institute, Training School Complex, Anushakti Nagar , Mumbai 400085, India
a r t i c l e i n f o a b s t r a c t
Article history:
Received
14 December 2017
Received
in revised form 4 April 2018
Accepted
6 April 2018
Available
online 9 April 2018
Editor: M.
Cveti
ˇ
c
Like BPS D3 brane, the non-supersymmetric (non-susy) D3 brane of type IIB string theory is also known
to have a decoupling limit and leads to a non-supersymmetric AdS/CFT correspondence. The throat
geometry in this case represents a QFT which is neither conformal nor supersymmetric. The ‘black’
version of the non-susy D3 brane in the decoupling limit describes a QFT at finite temperature. Here we
first compute the entanglement entropy for small subsystem of such QFT from the decoupled geometry of
‘black’ non-susy D3 brane using holographic technique. Then we study the entanglement thermodynamics
for the weakly excited states of this QFT from the asymptotically AdS geometry of the decoupled ‘black’
non-susy D3 brane. We observe that for small subsystem this background indeed satisfies a first law like
relation with a universal (entanglement) temperature inversely proportional to the size of the subsystem
and an (entanglement) pressure normal to the entangling surface. Finally we show how the entanglement
entropy makes a cross-over to the thermal entropy at high temperature.
© 2018 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
The entanglement entropy (EE) is a measure of quantum infor-
mation
encoded in a quantum system. In particular, for a bipartite
system the EE of a subsystem A is the von Neumann entropy and
is defined as S
A
=−Tr(ρ
A
log ρ
A
), where ρ
A
= Tr
B
(ρ
tot
) is the re-
duced
density matrix on A obtained by tracing out on B, the com-
plement
of A, of the density matrix of the total system ρ
tot
(see,
for example, [1–7] including some reviews). It is useful for many
body systems to describe various quantum phases of matter and
serves as an order parameter for the quantum phase transitions
which occur near zero temperature [8–12]. The density matrix can
be carefully defined in the continuum and therefore, EE can be cal-
culated
in a QFT in principle using the so-called replica trick (see,
for example [13]). However, the actual computation can be done
quite generally only in low dimensional CFT
d+1
(d < 2) [3,4]. For
higher dimensions the computation of EE becomes intractable ex-
cept
for some special cases, like free field QFT in three dimensions
and also for CFT
4
[13].
Ryu
and Takayanagi [14,15], motivated by the Bekenstein–
Hawking
entropy formula, gave a prescription to compute EE in
*
Corresponding author.
E-mail
addresses: aranya .bhattacharya @saha .ac .in (A. Bhattacharya),
shibaji .roy @saha .ac .in (S. Roy).
any dimensions using the idea of AdS/CFT [16,17]. According to
them, the holographic EE (HEE) of the subsystem A in the gravity
dual is given by [14]
S
E
=
Area(γ
min
A
)
4G
N
(1)
where γ
min
A
is the d-dimensional minimal area (time-sliced)
surface in AdS
d+2
space whose boundary matches with the
boundary of the subsystem A, i.e., ∂γ
min
A
= ∂ A and G
N
is the
(d + 2)-dimensional Newton’s constant. The HEE given in (1) has
been checked [14]to agree with the QFT results in lower di-
mensions.
In higher dimensions also they give correct qualitative
behaviors. In thermodynamics the entropy of a system can be
increased by injecting energy to the system, where the proportion-
ality
constant is given by the inverse of temperature. This leads
to an energy conservation relation E = T S, the first law of
thermodynamics. An analogous problem was addressed in [18]for
the EE, i.e., to see how the EE of a certain region grows with the
increase in energy. Here the EE is computed using AdS/CFT. The
excited state of a CFT is given by the deformation of AdS whose EE
can be computed using (1). This is then compared with the time
component of the boundary stress tensor T
tt
or the energy density.
For a small subsystem A, the total energy is found to be propor-
tional
to the increase in EE and the proportionality constant is c/,
https://doi.org/10.1016/j.physletb.2018.04.011
0370-2693/
© 2018 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
.