arXiv subjects

Peter Szabo

Publications and source records attributed to Peter Szabo.

7 recordsLinked to original sources

arXiv2025

The Optical to X-ray Luminosity and Spectrum of Supernova Wind Breakouts

Observations indicate that optically thick circum-stellar medium (CSM) at radii of $10^{14}-10^{15}~$cm around Type II core-collapse supernovae (SN) progenitors is common (and may be present in other types of massive star explosions). The breakout of the SN radiation-mediated shock (RMS) through such CSM leads to the formation of a collisionless shock (CLS). We analyze the evolution of the shock structure and associated radiation field during and after the RMS-CLS transition for non-relativistic shock breakout velocity ($v_{\rm bo}=10^9v_9~{\rm cm/s}<0.1c$) through a hydrogen-rich CSM ``wind" density profile, $\rho\propto r^{-2}$, with breakout radius $R_{{\rm bo}}=10^{14}R_{14}~$cm much larger than the progenitor radius. An analytic description of the key properties of the emitted optical to X-ray radiation is provided, supported by numeric radiation-hydrodynamics calculations self-consistently describing the time-dependent spatial distribution of the plasma and radiation, governed by Bremsstrahlung emission/absorption and inelastic Compton scattering. The characteristic energy of the photons carrying most of the luminosity, $\approx10^{43}R_{14}v_9^2~$erg/s, shifts from UV to X-ray, reaching 1~keV as the shock reaches $\approx3R_{\rm bo}$, in $\approx3R_{14}/v_9~$d. The X-ray signal is not suppressed by propagation through the upstream wind, and its absence may suggest that the dense CSM does not extend much beyond $R_{\rm bo}$. Our results provide the basis for a quantitative calculation of the high energy $\gamma$-ray and neutrino emission that is expected from particles accelerated at the CLS, and will allow using data from upcoming surveys that will systematically detect large numbers of young SNe, particularly ULTRASAT, to infer the pre-explosion mass loss history of the SN progenitor population.

astro-ph.HE↗

arXiv2022

Four-Dimensional Scaling of Dipole Polarizability in Quantum Systems

Polarizability is a key response property of physical and chemical systems, which has an impact on intermolecular interactions, spectroscopic observables, and vacuum polarization. The calculation of polarizability for quantum systems involves an infinite sum over all excited (bound and continuum) states, concealing the physical interpretation of polarization mechanisms and complicating the derivation of efficient response models. Approximate expressions for the dipole polarizability, $α$, rely on different scaling laws $α\propto$ $R^3$, $R^4$, or $R^7$, for various definitions of the system radius $R$. Here, we consider a range of single-particle quantum systems of varying spatial dimensionality and having qualitatively different spectra, demonstrating that their polarizability follows a universal four-dimensional scaling law $α= C (4 μq^2/\hbar^2)L^4$, where $μ$ and $q$ are the (effective) particle mass and charge, $C$ is a dimensionless excitation-energy ratio, and the characteristic length $L$ is defined via the $\mathcal{L}^2$-norm of the position operator. %The applicability of this unified formula is demonstrated by accurately predicting the dipole polarizability of 36 atoms and 1641 small organic~molecules. This unified formula is also applicable to many-particle systems, as shown by} accurately predicting the dipole polarizability of 36 atoms, 1641 small organic \rrr{molecules, and Bloch electrons in periodic systems.

quant-ph↗

arXiv2018

A Viscoelastic Catastrophe

We use a differential constitutive equation to model the flow of a viscoelastic flow in a cross-slot geometry, which is known to exhibit bistability above a critical flow rate. The novelty lies in two asymmetric modifications to the geometry, which causes a change in the bifurcation diagram such that one of the stable solutions becomes disconnected from the solution at low flow speeds. First we show that it is possible to mirror one of the modifications such that the system can be forced to the disconnected solution. Then we show that a slow decrease of the flow rate, can cause the system to go through a drastic change on a short time scale, also known as a catastrophe. The short time scale could lead to a precise and simple experimental measurement of the flow conditions at which the viscoelastic catastrophe occurs. Since the phenomena is intrinsically related to the extensional rheology of the fluid, we propose to exploit the phenomena for in-line extensional rheometry.

physics.flu-dyn↗

arXiv2014

Plastic strain is a mixture of avalanches and quasi-reversible deformations: Study of various sizes

Size-dependence of plastic flow is studied by discrete dislocation dynamical simulation of systems with various numbers of interacting linear edge dislocations while the stress is slowly increased. Regions between avalanches in the individual stress curves as functions of the plastic strain were found nearly linear and reversible, where the plastic deformation obeys an effective equation of motion with a nearly linear force. For small plastic deformation, the means of the stress-strain curves are power law over two decades. Here and for somewhat larger plastic deformations, the mean stress-strain curves converge for larger sizes, while their variances shrink, both indicating the existence of a thermodynamical limit. The converging averages decrease with increasing size, in accordance with size-effects from experiments. For large plastic deformations, where steady flow sets in, thermodynamical limit was not realized in this model system.

cond-mat.mtrl-sci↗

arXiv2008

Turning with the others: novel transitions in an SPP model with coupling of accelerations

We consider a three dimensional, generalized version of the original SPP model for collective motion. By extending the factors influencing the ordering, we investigate the case when the movement of the self-propelled particles (SPP-s) depends on both the velocity and the acceleration of the neighboring particles, instead of being determined solely by the former one. By changing the value of a weight parameter s determining the relative influence of the velocity and the acceleration terms, the system undergoes a kinetic phase transition as a function of a behavioral pattern. Below a critical value of s the system exhibits disordered motion, while above it the dynamics resembles that of the SPP model. We argue that in nature evolutionary processes can drive the strategy variable s towards the critical point, where information exchange between the units of a system is maximal.

cond-mat.stat-mech↗

arXiv2002

On the Role of External Constraints in a Spatially Extended Evolutionary Prisoner's Dilemma Game

We study the emergency of mutual cooperation in evolutionary prisoner's dilemma games when the players are located on a square lattice. The players can choose one of the three strategies: cooperation (C), defection (D) or "tit for tat" (T), and their total payoffs come from games with the nearest neighbors. During the random sequential updates the players adopt one of their neighboring strategies if the chosen neighbor has higher payoff. We compare the effect of two types of external constraints added to the Darwinian evolutionary processes. In both cases the strategy of a randomly chosen player is replaced with probability P by another strategy. In the first case, the strategy is replaced by a randomly chosen one among the two others, while in the second case the new strategy is always C. Using generalized mean-field approximations and Monte Carlo simulations the strategy concentrations are evaluated in the stationary state for different strength of external constraints characterized by the probability P.

cond-mat.stat-mech↗

arXiv2000

Spatial evolutionary prisoner's dilemma game with three strategies and external constraints

The emergence of mutual cooperation is studied in a spatially extended evolutionary prisoner's dilemma game in which the players are located on the sites of cubic lattices for dimensions d=1, 2, and 3. Each player can choose one of the three strategies: cooperation (C), defection (D) or Tit for Tat (T). During the evolutionary process the randomly chosen players adopt one of their neighboring strategies if the chosen neighbor has higher payoff. Morover, an external constraint imposes that the players always cooperate with probability p. The stationary state phase diagram are computed by both using generalized mean-field approximations and Monte Carlo simulations. Nonequilibrium second order phase transitions assosiated with the extinction of one of the possible strategies are found and the corresponding critical exponents belong to the directed percolation universality class. It is shown that forcing externally the collaboration does not always produce the desired result.

cond-mat.stat-mech↗