Eur. Phys. J. C (2018) 78:106
https://doi.org/10.1140/epjc/s10052-018-5581-y
Regular Article - Theoretical Physics
Effects of cosmic-string framework on the thermodynamical
properties of anharmonic oscillator using the ordinary statistics
and the q-deformed superstatistics approaches
Hadi Sobhani
1,a
, Hassan Hassanabadi
1
, Won Sang Chung
2
1
Faculty of Physics, Shahrood University of Technology, P. O. Box 3619995161-316, Shahrood, Iran
2
Department of Physics and Research Institute of Natural Science, College of Natural Science, Gyeongsang National University, Jinju 52828,
Korea
Received: 21 July 2017 / Accepted: 23 January 2018
© The Author(s) 2018. This article is an open access publication
Abstract In this article, we determine the thermodynami-
cal properties of the anharmonic canonical ensemble within
the cosmic-string framework. We use the ordinary statis-
tics and the q-deformed superstatistics for this study. The
q-deformed superstatistics is derived by modifying the prob-
ability density in the original superstatistics. The Schrödinger
equation is rewritten in the cosmic-string framework. Next,
the anharmonic oscillator is investigated in detail. The wave
function and the energy spectrum of the considered system
are derived using the bi-confluent Heun functions. In the
next step, we first determine the thermodynamical proper-
ties for the canonical ensemble of the anharmonic oscillator
in the cosmic-string framework using the ordinary statistics
approach. Also, these quantities have been obtained in the q-
deformed superstatistics. For vanishing deformation param-
eter, the ordinary results are obtained.
1 Introduction
Topological defects were first theorized by Kibble [1].
These defects are physical structures produced in symmetry-
breaking phase transitions in the early universe. Among all
the possible types of defects, the one-dimensional cosmic
strings are the focus of most of the studies in this area [2]. This
is because of the compatibility with the current cosmological
models and their association with several brane inflation sce-
narios [3,4] and super-symmetric grand unified theories [5].
These are constrained by the cosmic microwave background
[6–10] and gravitational wave facilities [11–15]. In recent
developments, cosmic strings have been considered to study
solutions of black holes [16], to investigate the average rate of
change of energy for a static atom immersed in a thermal bath
a
e-mail: hadisobhani8637@gmail.com
of electromagnetic radiation [17], to study Hawking radia-
tion of massless and massive charged particles [18], to study
the non-Abelian Higgs model coupled with gravity [19], in
the quantum dynamics of scalar bosons [20], in hydrody-
namics [21], to study the non-relativistic motion of a quan-
tum particle subjected to magnetic field [22], to investigate
dynamical solutions in the context of super-critical tensions
[23], describing scattering states of the Dirac equation in the
presence of cosmic string for Coulomb interaction [24] and
to study the spin-zero Duffin–Kemmer–Petiau equation in a
cosmic-string space-time with the Cornell interaction [25].
The concept of superstatistics was initiated by Beck and
Cohen [26]. They considered non-equilibrium systems with
complex dynamics in stationary states with large fluctuations
of intensive quantities on large time scales. Depending on the
statistical properties of the fluctuations, they obtain different
effective statistical mechanical descriptions. To derive and
compute macroscopic quantities such as the Helmholtz free
energy, the entropy, and the mean energy, the Boltzmann fac-
tor e
β E
is the essential tool; here β =
1
k
B
T
with k
B
being the
Boltzmann constant and T denoting the temperature. But this
condition no longer will exist when the equilibrium condi-
tions are lost. As a result, therefore, we need to define an
effective Boltzmann factor B(E) as
B(E) =
∞
0
e
β
E
f (β
0
,β)dβ
(1.1)
where f (β
,β)is a probability density and, according to the
definition (1.1), this is an average of the ordinary Boltzmann
factor. Referring to Ref. [26], the probability density must
obey the conditions:
123