arXiv subjects

Balázs Endre Szigeti

Publications and source records attributed to Balázs Endre Szigeti.

8 recordsLinked to original sources

arXiv2026

On the Stability of the Euler-Poisson Dark-Fluid Model

We present a stability analysis of a dark-fluid model described as a non-relativistic, rotating, non-viscous, self-gravitating fluid. We assume spherical symmetry and model the matter by a polytropic equation of state. The resulting coupled nonlinear partial differential equation system is solved using a self-similar ansatz known from the Guderley-Landau-Stanyukovich problem. We find that three of the four Lyapunov exponents are negative, while only one is positive. This indicates one unstable direction and three contracting directions in phase space. The single positive exponent is relatively small, suggesting that the self-similar solution is only weakly unstable and remains dynamically robust over the investigated interval.

gr-qc↗

arXiv2026

The Formulation of Scaling Expansion in an Euler-Poisson Dark-fluid Model

We present a dark fluid model described as a non-viscous, non-relativistic, rotating, and self-gravitating fluid. We assumed that the system has spherical symmetry and the matter can be described with the polytropic equation of state. The induced coupled non-linear partial differential equation system was solved by using a self-similar time-dependent ansatz introduced by L. Sedov and G. I. Taylor. These kinds of solutions were successfully used to describe blast waves induced by an explosion since the Guderley-Landau-Stanyukovich problem. We showed that these kinds of solutions can provide new solutions that are consistent with the Newtonian cosmological framework. We have found that such solutions can be applied to describe normal-to-dark energy on the cosmological scale.

physics.flu-dyn↗

arXiv2025

Asymptotic evolution of bulk-viscous, spherically symmetric spacetimes

The scale-free nature of gravitational interaction in both Newtonian gravity and the general theory of relativity gives rise to the concept of self-similarity, where solutions are scale invariant. As a result of this property, the governing partial differential equations are greatly simplified and can be transformed into ordinary ones. These solutions function as attractors, characterizing the asymptotic dynamics of more general solutions. There exist situations in which self-similarity is only partially realized, giving rise to kinematic self-similar solutions. Our study provides a systematic classification of kinematic self-similar solutions corresponding to the most general spherically symmetric spacetime in the presence of bulk viscous flows.

gr-qc↗

arXiv2025

Cylindrical Euler--Poisson Equation in a Chaplygin Gas Medium

We studied the Euler--Poisson equation system in the case of cylindrical symmetry with the von Neumann--Sedov--Taylor type of self-similar Ansatz and present scaling solutions. We have analyzed the scenario governed by Chaplygin's equation of state, which has historically been studied as a unifying framework of dark fluid for dark matter and dark energy.

math-ph↗

arXiv2025

Can Rotation Solve the Hubble Puzzle?

The discrepancy between low and high redshift Hubble constant $H_0$ measurements is the highest significance tension within the concordance $Λ$CDM paradigm. If not due to unknown systematics, the Hubble puzzle suggests a lack of understanding of the universe's expansion history despite the otherwise spectacular success of the theory. We show that a Gödel inspired slowly rotating dark-fluid variant of the concordance model resolves this tension with an angular velocity today $ω_0 \simeq 2\times 10^{-3}$~Gyr\textsuperscript{-1}. Curiously, this is close to the maximal rotation, avoiding closed time-like loops with a tangential velocity less than the speed of light at the horizon.

gr-qc↗

arXiv2021

Estimating Microscopic Nuclear Data by Compact Star Observations

We studied recent observation data of pulsar masses and radii of PSR J0740$+$6620, PSR J0348$+$0432, and PSR J1614$-$2230 from different measurements, based on the extended version of $σ$-$ ω$ model. Throughout our analysis, we assumed that these pulsars are maximal-mass compact stars, thus we applied the core approximation. Based on the linear relation between the microscopic and macroscopic parameters of compact stars evaluated by our model, we estimated the average Landau mass $m_L = 752.46^{+49.1}_{-42.5}$ MeV and compressibility $K = 261.7^{+57.2}_{-28.0}$ MeV.

nucl-th↗

arXiv2019

Short time behavior of continuous time quantum walks on graphs

Dynamical evolution of systems with sparse Hamiltonians can always be recognized as continuous time quantum walks (CTQWs) on graphs. In this paper, we analyze the short time asymptotics of CTQWs. In recent studies, it was shown that for the classical diffusion process the short time asymptotics of the transition probabilities follows power laws whose exponents are given by the usual combinatorial distances of the nodes. Inspired by this result, we perform a similar analysis for CTQWs both in closed and open systems, including time-dependent couplings. For time-reversal symmetric coherent quantum evolutions, the short time asymptotics of the transition probabilities is completely determined by the topology of the underlying graph analogously to the classical case, but with a doubled power-law exponent. Moreover, this result is robust against the introduction of on-site potential terms. However, we show that time-reversal symmetry breaking terms and non-coherent effects can significantly alter the short time asymptotics. The analytical formulas are checked against numerics, and excellent agreement is found. Furthermore, we discuss in detail the relevance of our results for quantum evolutions on particular network topologies.

quant-ph↗

arXiv2019

Study of angular correlations in Monte Carlo simulations

In two-particle angular correlation measurements the distribution of charged hadron pairs are evaluated as a function of pseudorapidity ($Δη$) and azimuthal ($Δφ$) differences. In these correlations, jets manifest themselves as a near-side peak around $Δη= 0,$ $Δφ= 0$. These correlations can be used to extract transverse momentum ($p_T$) and centrality dependence of the shape of the near-side peak in Pb-Pb collision. The shape of the near-side peak is quantified by the variances of the distribution. The variances are evaluated from a fit combining the peak and the background. In this contribution, identified and unidentified angular correlations are shown from Pb-Pb collisions at $\sqrt{s_{NN}} = 2.76$ TeV from Monte Carlo simulations (AMPT, PYTHIA 8.235/Angantyr). Results show that transport models in AMPT give better results than PYTHIA 8.235/Angantyr when comparing to the experimental results of the ALICE collaboration.

hep-ph↗