arXiv subjects

E. Siri

Publications and source records attributed to E. Siri.

5 recordsLinked to original sources

arXiv2026

Weak Bose-Einstein condensation in a rigidly rotating magnetized charged Bose gas

We investigate the weak Bose-Einstein condensation (BEC) scenario of a noninteracting charged Bose gas simultaneously subjected to a strong magnetic field and rigid rotation. Using standard methods of finite-temperature quantum field theory and the generalized Fock-Schwinger formalism, we derive the corresponding thermodynamic potential in the nonrelativistic and lowest Landau level approximations. An appropriate modification of the effective chemical potential yields a consistent thermodynamic description and naturally introduces a magnetorotational fugacity. Within the high-temperature approximation, rigid rotation enters the thermodynamics solely through the Tolman-Ehrenfest local temperature. We demonstrate that rigid rotation does not qualitatively modify the weak BEC scenario induced by Landau quantization. The magnetorotational fugacity remains below unity throughout the phenomenologically relevant temperature range, while the continuous evolution of the ground state population and the absence of a singularity in the specific heat provide complementary signatures of the persistence of weak BEC. We further study the thermodynamic properties of the system under conditions relevant to quark-gluon plasma and neutron-star matter. We show that rotational effects are much more pronounced in the former. Our analysis reveals a new magnetic response to rigid rotation: while magnetic fields enhance diamagnetism, rotation drives it toward paramagnetism. This behavior reflects a competition between magnetic quantization and rotational orbital motion, emphasizing the role of rotation in shaping the magnetic response of bosonic matter.

hep-ph↗

arXiv2025

Spontaneous breaking of global U(1) symmetry in an interacting Bose gas under rigid rotation

We investigate the impact of rigid rotation on the spontaneous breaking of U(1) symmetry in a Bose gas, which is described by a self-interacting complex scalar field Lagrangian. Rigid rotation is introduced through a specific metric that explicitly depends on the angular velocity $\Omega$. We begin by determining the free propagator for this model at finite temperature $T$ and chemical potential $\mu$. Using this propagator, we calculate the thermodynamic potential in terms of an energy dispersion relation $\epsilon_{k}$. It is found that in both the U(1) symmetric phase and the symmetry-broken phase, two energy branches emerge. In the symmetry-broken phase, they are identified with a massive phonon and a massless roton mode. Notably, rotation does not alter $\epsilon_{k}$ at low momentum. Setting $\mu=0$, we use the total thermodynamic potential, which includes classical, thermal, vacuum, and nonperturbative ring contributions, to explore how the condensate depends on $T$ and $\Omega$. We first focus on the classical and thermal parts of the thermodynamic potential and find that the critical temperature of the U(1) phase transition scales as $\Omega^{1/3}$. By identifying the (pseudo-)Goldstone and non-Goldstone modes of this model with $\pi$ and $\sigma$ mesons, we calculate the $T$ and $\Omega$ dependence of masses $m_{\pi}$ and $m_{\sigma}$. We demonstrate that the Goldstone theorem holds only when the one-loop (thermal) corrections to $m_{\sigma}$ and $m_{\pi}$ are taken into account. We further explore the $T$ and $\Omega$ dependence of the condensate, determine the $\sigma$ dissociation temperatures for fixed $\Omega$, and compare them with the critical temperature of the phase transition. Additionally, we emphasize the role played by the nonperturbative ring potential, especially in altering the order of the phase transition with and without rotation.

hep-ph↗

arXiv2024

Bose-Einstein condensation in a rigidly rotating relativistic boson gas

We study the Bose-Einstein condensation (BEC) of a free Bose gas under rigid rotation. The aim is to explore the impact of rotation on the thermodynamic quantities associated with BEC, including the Bose-Einstein (BE) transition temperature and condensate fraction. We begin by introducing the rotation in the Lagrangian density of free charged Klein-Gordon fields and determine the corresponding grand canonical partition function at finite temperature, chemical potential, and finite angular velocity. Assuming slow rotation, we derive analytical expressions for the pressure, energy, number, and angular momentum densities of a free Bose gas in nonrelativistic and ultrarelativistic limits in terms of the corresponding fugacities. We then focus on the phenomenon of BEC. We calculate the critical temperature of BEC transition and the condensate fraction in a slowly rotating Bose gas including only particles. Our findings indicate that the critical exponent associated with the BE transition in a rotating gas is lower compared to that in a nonrotating Bose gas. We also determine the fugacity in a rotating Bose gas in the aforementioned limits and examine how rotation affects its temperature dependence, both below and above the critical temperature. By analyzing the behavior of heat capacity at these temperatures, we demonstrate that in a nonrelativistic Bose gas, the rotation transforms the nature of the BE phase transition from a continuous to a discontinuous transition. In general, we find that a nonrelativistic Bose gas under rotation behaves similarly to a nonrotating Bose gas in ultrarelativistic limit.

hep-ph↗

arXiv2024

Boson propagator under rigid rotation; Mode expansion approach

To explore how rigid rotation affects the thermodynamic properties of free relativistic bosons, we employ the standard imaginary time formalism of thermal field theory to calculate the free propagator of complex scalar fields under rotation. We introduce the corresponding partition function and explicitly compute it by expanding the modes in cylindrical coordinates. The resulting propagator is in full agreement with similar findings in the existing literature.

hep-ph↗

arXiv2024

Thermodynamic properties of a relativistic Bose gas under rigid rotation

We study the thermodynamic properties of a rigidly rotating relativistic Bose gas. First, we derive the solution of the equation of motion corresponding to a rotating complex Klein-Gordon field and determine the free propagator of this model utilizing the Fock-Schwinger proper-time method. Using this propagator, we then obtain the thermodynamic potential of this model in the zeroth and first perturbative level. In addition, we compute the nonperturbative ring contribution to this potential. Our focus is on the dependence of these expressions on the angular velocity, which effectively acts as a chemical potential. Using this thermodynamic potential, we calculate several quantities, including the pressure, angular momentum and entropy densities, heat capacity, speed of sound, and moment of inertia of this rigidly rotating Bose gas as functions of temperature ($T$), angular velocity ($\Omega$), and the coupling constant ($\alpha$). We show that certain thermodynamic instabilities appear at high temperatures and large couplings. They are manifested as zero and negative values of the above quantities, particularly the moment of inertia and heat capacity. Zero moment of inertia leads to the phenomenon of supervorticity at certain $T$ or $\alpha$. Supervortical temperatures (couplings) decrease with increasing coupling (temperature). We also observe superluminal sound velocities at high $T$ and for large $\alpha$.

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