Physics Letters B 771 (2017) 583–587
Contents lists available at ScienceDirect
Physics Letters B
www.elsevier.com/locate/physletb
Entanglement entropy in a non-conformal background
M. Rahimi, M. Ali-Akbari
∗
, M. Lezgi
Department of Physics, Shahid Beheshti University G.C., Evin, Tehran 19839, Iran
a r t i c l e i n f o a b s t r a c t
Article history:
Received
14 March 2017
Received
in revised form 16 May 2017
Accepted
19 May 2017
Available
online 8 June 2017
Editor:
N. Lambert
We use gauge-gravity duality to compute entanglement entropy in a non-conformal background with an
energy scale . At zero temperature, we observe that entanglement entropy decreases by raising .
However, at finite temperature, we realize that both
T
and entanglement entropy rise together.
Comparing entanglement entropy of the non-conformal theory, S
A(N)
, and of its conformal theory at
the UV limit, S
A(C)
, reveals that S
A(N)
can be larger or smaller than S
A(C)
, depending on the values of
and T .
© 2017 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 AdS/CFT correspondence states that type IIB string theory
on the AdS
5
× S
5
background is dual to N =4 SU(N
c
) supercon-
formal
gauge theory in a four-dimensional Minkowski space-time
living on the boundary of the AdS
5
background [1,2]. This out-
standing
correspondence is a strong–weak duality which makes
it possible to investigate various strongly coupled systems. As a
matter of fact, in the large number of colors and large ’t Hooft
coupling
constant limit, the gauge theory is still a quantum the-
ory
but strongly coupled. However, the string theory reduces to
a classical gravity which is a weakly coupled theory. Therefore,
different questions in the strongly coupled gauge theory can be
translated into corresponding problems in the classical gravity. This
duality has been frequently applied to study various aspects of
the strongly coupled systems such as quantum chromodynamics,
quark–gluon plasma and condense matter, for instance see [3–5].
Since
the AdS/CFT correspondence, or more generally gauge-
gravity
duality, applies to the non-conformal gauge theories as well
as conformal ones, studying various effects of the non-conformal
behavior on the physical quantities is always an attractive prob-
lem.
A new family of solutions of a five-dimensional gravity model,
including Einstein gravity coupled to a scalar field with a non-
trivial
potential, has been recently introduced and studied in [6].
The corresponding four-dimensional strongly coupled gauge the-
ory
is not conformal and the theory has conformal fixed points at
IR as well as at UV. This means that these solutions are asymptotic
*
Corresponding author.
E-mail
addresses: me_rahimi@sbu.ac.ir (M. Rahimi), m_aliakbari@sbu.ac.ir
(M. Ali-Akbari),
mahsalezgee@yahoo.com (M. Lezgi).
to the AdS
5
in the UV and IR limits with different radii. Different
properties of the above background such as thermodynamics and
relaxation channels have been studied [6].
One
interesting physical quantity, on the gauge theory side, is
entanglement entropy [8]. In the literature, gauge-gravity duality
has been applied to investigate entanglement entropy success-
fully.
For example, entanglement entropy is also helpful to probe
a confinement–deconfinement phase transition at zero tempera-
ture
in confining theories [11]. Then search for transition has also
been extended to non-conformal gauge theories at finite temper-
ature [12].
It is shown that no transition takes place at finite
temperature. In this paper we study the effect of introducing an
energy scale on the entanglement entropy and to check the possi-
bility
of a phase transition in such a case.
1
2. Model
Here we review the non-conformal background introduced
in [6]. The background is a solution of five-dimensional gravity
theory coupled to a scalar field with a non-trivial potential. The
action of the gravity theory is given by
S =
2
G
2
5
d
5
x
√
−g
1
4
R −
1
2
(∇φ)
2
− V (φ)
, (1)
where G
5
is the five-dimensional Newton constant. The particular
form of the potential is
1
It is also important to notice that, in [13], it is argued that entanglement en-
tropy
is more relevant timescale for the approach to equilibrium than two-point
function and Wilson loop.
http://dx.doi.org/10.1016/j.physletb.2017.05.055
0370-2693/
© 2017 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
.