Physics Letters B 800 (2020) 135093
Contents lists available at ScienceDirect
Physics Letters B
www.elsevier.com/locate/physletb
Instability of Higgs vacuum via string cloud
Issei Koga
a
, Sachiko Kuroyanagi
b,c
, Yutaka Ookouchi
d,a,∗
a
Department of Physics, Kyushu University, Fukuoka 819-0395, Japan
b
Department of Physics, Nagoya University, Nagoya 464-8602, Japan
c
Instituto de Física Teórica, Universidad Autonóma de Madrid, 28049 Madrid, Spain
d
Faculty of Arts and Science, Kyushu University, Fukuoka 819-0395, Japan
a r t i c l e i n f o a b s t r a c t
Article history:
Received
9 October 2019
Received
in revised form 5 November 2019
Accepted
8 November 2019
Available
online 13 November 2019
Editor:
M. Cveti
ˇ
c
We study the instability of the Higgs vacuum caused by a cloud of strings. By catalysis, the decay rate
of the vacuum is highly enhanced and, when the energy density of the cloud is larger than the critical
value, a semi-classical vacuum decay occurs. We also discuss the relation between the string cloud and
observational constraints on the cosmic strings from the viewpoint of the catalysis, which are converted
into bounds on the parameters of the Higgs potential.
© 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
The discovery of the Higgs particle and the precise measure-
ments
of the top quark mass seems to reveal that our vacuum, in
which the electroweak symmetry breaks down (we call the Higgs
vacuum for short), is metastable [1]. This fact has been boosting
studies on the Higgs vacuum from various point of views [2]. These
decay processes are known as the homogeneous vacuum decay. On
the other hand, the inhomogeneous vacuum decay, initiated by [3],
can occur in nature. The idea was later applied to phenomenologi-
cal
model building [4] and the vacuum decay in string theories [5]
and
gravity theories [6–10]. Among them, the black hole catalysis
discussed in [6,7]is interesting because it is generally applicable to
various settings; The catalysis seeded by a topological soliton [3,4]
highly
depends on the structure of the potential. Typically, the soli-
ton
is stabilized by the topological charge related to the symmetry
breaking. For the catalysis to work in this case, the true vacuum
has to be connected to the symmetry restoring point of the poten-
tial
as emphasized in [4].
The
catalytic effects caused by the string cloud [11]was re-
cently
discussed in the context of the creation of the bubble Uni-
verse
in five dimensions proposed in [12]. The catalysis provided
a kind of the selection rule to the cosmological constant [13]. In
this paper, with the aim of getting interesting phenomenology, we
apply the method to the decay of the Higgs particle in the stan-
dard
model, basically along the lines of [8]. We then study the
relation between the cloud of string and cosmological observa-
*
Corresponding author.
E-mail
address: yutaka.ookouchi@artsci.kyushu-u.ac.jp (Y. Ookouchi).
tions by showing how to connect the Higgs potential with the
cosmic string tension. If the cloud of strings exists in nature, it
can leave signatures in the cosmic microwave background (CMB)
and gravitational wave probes by pulsar timing arrays and laser
interferometers. Assuming that the string cloud network behaves
as the standard scaling cosmic string network, we apply cosmo-
logical
bounds on the tension to obtain constraints on parameters
of the Higgs potential. We also consider how future gravitational
wave observations can help to test the scenario of Higgs vacuum
decay through the catalytic effect of the string cloud. On the con-
trary,
if the Higgs potential parameters are determined by future
collider experiments, one can infer the string tension, which can
be used mutually with cosmological observations.
The
organization of this paper is as follows. In section 2, we
briefly review the method discussed in [14,15,6,7] and apply to
the decay of de Sitter to anti-de Sitter (AdS) vacua catalyzed by a
cloud of strings [11]in the aim of application to the Higgs vacuum
decay. We show that there exists the critical value above which
semi-classical decay occurs rather than quantum tunneling. In sec-
tion 3,
we discuss the instability of the Higgs vacuum. In section 4,
we investigate a connection between a string cloud and cosmolog-
ical
constraints on cosmic strings. From this, we study constraints
for the parameters of Higgs potential. The section 5 is devoted to
conclusions.
2. The catalytic decay of de Sitter vacua
In this section, first we review the general study on the catalytic
decay of vacua discussed in [15,6,9], and then we apply it to the
cloud of strings. We compute the bounce action for the decay of
https://doi.org/10.1016/j.physletb.2019.135093
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© 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
.