Physics Letters B 772 (2017) 189–193
Contents lists available at ScienceDirect
Physics Letters B
www.elsevier.com/locate/physletb
On the stability of non-supersymmetric supergravity solutions
Ali Imaanpur
∗
, Razieh Zameni
Department of Physics, School of sciences, Tarbiat Modares University, P.O. Box 14155-4838, Tehran, Iran
a r t i c l e i n f o a b s t r a c t
Article history:
Received
21 February 2017
Received
in revised form 11 June 2017
Accepted
12 June 2017
Available
online 20 June 2017
Editor: N.
Lambert
We examine the stability of some non-supersymmetric supergravity solutions that have been found
recently. The first solution is AdS
5
× M
6
, for M
6
an stretched CP
3
. We consider breathing and squashing
mode deformations of the metric, and find that the solution is stable against small fluctuations of this
kind. Next we consider type IIB solution of AdS
2
× M
8
, where the compact space is a U (1) bundle over
N(1, 1). We study its stability under the deformation of M
8
and the 5-form flux. In this case we also find
that the solution is stable under small fluctuation modes of the corresponding deformations.
© 2017 The Author(s). 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
Selecting a stable solution among the many candidate super-
gravity
solutions is a major problem in any Kaluza–Klein compact-
ification.
One way to guarantee the stability is to demand that the
solution preserve a portion of supersymmetry [1–3]. In the absence
of supersymmetry, on the other hand, it is difficult to conclude
whether a particular solution is stable. In fact, one needs to exam-
ine
the stability under small perturbations in all possible directions
of the potential. Moreover, even if a solution is stable under such
small perturbations, there still remains the question of stability un-
der
nonperturbative effects [4]. Finding non-supersymmetric stable
solutions, however, becomes important if we are to construct real-
istic
phenomenological models in which supersymmetry is sponta-
neously
broken.
Freund–Rubin
solutions can be divided into two main classes
depending on whether or not the compact space encompasses
(electric) fluxes [5,6]. When the flux has components only along
the Ad S direction, it has been observed that the majority of so-
lutions
either preserve supersymmetry (and hence stable), or at
least are perturbatively stable. For solutions that support flux in
the compact direction (Englert type), however, supersymmetry is
often broken. They are in fact suspected to be unstable, though,
the direct computation of mass spectrum and determination of sta-
bility
is more involved. Englert type solution of AdS
4
× S
7
, for in-
stance,
was shown to be unstable [7], and this was further general-
ized
to seven dimensional spaces which admit at least two Killing
*
Corresponding author.
E-mail
addresses: aimaanpu@modares.ac.ir (A. Imaanpur),
r.zameni@modares.ac.ir (R. Zameni).
spinors [8]. Pope–Warner solution is another non-supersymmetric
example which supports flux in the compact direction [9], and was
proved to be unstable much later [10]. Englert type solutions, in
spite of their possible instability, have played a key role in studying
the holographic superconductors. By employing similar techniques
that we use in this paper, domain wall solutions were found that
interpolate between the Englert type and the skew-whiffed solu-
tions.
The domain wall solutions were then used to describe holo-
graphic
superconductor phase diagrams [11].
The
stability of Freund–Rubin type geometries of the form
Ad S
p
× M
q
, where AdS
p
is anti-de Sitter spacetime and M
q
a
compact manifold, has also increasingly been studied after the dis-
covery
of the AdS/CFT correspondence [12]. Stability is important
for understanding a possible dual conformal field theory (CFT) de-
scription.
For stable solutions, the spectrum of the masses directly
yields the dimensions of certain operators in such a CFT. Unstable
solutions can still have a dual CFT description but the physics is
different [13]. Since the curvature of Ad S is negative, not all the
tachyonic modes lead to instability. In fact, scalars with m
2
< 0
may
also appear if their masses are not below a bound set by the
curvature scale of Ad S [3].
Recently,
some new non-supersymmetric compactifying solu-
tions
of eleven-dimensional supergravity and type IIB supergravity
have been found [14,15]. Specifically, the eleven-dimensional su-
pergravity
solution consists of AdS
5
× M
6
, where for M
6
there
are two possible choices. For the first solution M
6
is CP
3
with
the standard Fubini-Study metric, which was derived and studied
in [16], and it was further shown that is perturbatively stable [17].
For the second solution S
2
fibers of CP
3
are slightly stretched with
respect to the base manifold. Type IIB solution, on the other hand,
is AdS
2
× M
8
, where M
8
is a U(1) bundle over N(1, 1). All these
http://dx.doi.org/10.1016/j.physletb.2017.06.029
0370-2693/
© 2017 The Author(s). 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
.