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Nikos Kalogeropoulos

Publications and source records attributed to Nikos Kalogeropoulos.

28 records · Page 2Linked to original sources
arXiv2011

Distributivity and deformation of the reals from Tsallis entropy

We propose a one-parameter family \ $\mathbb{R}_q$ \ of deformations of the reals, which is motivated by the generalized additivity of the Tsallis entropy. We introduce a generalized multiplication which is distributive with respect to the generalized addition of the Tsallis entropy. These operations establish a one-parameter family of field isomorphisms \ $τ_q$ \ between \ $\mathbb{R}$ \ and \ $\mathbb{R}_q$ \ through which an absolute value on \ $\mathbb{R}_q$ \ is introduced. This turns out to be a quasisymmetric map, whose metric and measure-theoretical implications are pointed out.

math-ph↗
arXiv2008

Phase space measure concentration for an ideal gas

We point out that a special case of an ideal gas exhibits concentration of the volume of its phase space, which is a sphere, around its equator in the thermodynamic limit. The rate of approach to the thermodynamic limit is determined. Our argument relies on the spherical isoperimetric inequality of Lévy and Gromov.

cond-mat.stat-mech↗
arXiv2008

The geodesic rule for higher codimensional global defects

We generalize the geodesic rule to the case of formation of higher codimensional global defects. Relying on energetic arguments, we argue that, for such defects, the geometric structures of interest are the totally geodesic submanifolds. On the other hand, stochastic arguments lead to a diffusion equation approach, from which the geodesic rule is deduced. It turns out that the most appropriate geometric structure that one should consider is the convex hull of the values of the order parameter on the causal volumes whose collision gives rise to the defect. We explain why these two approaches lead to similar results when calculating the density of global defects by using a theorem of Cheeger and Gromoll. We present a computation of the probability of formation of strings/vortices in the case of a system, such as nematic liquid crystals, whose vacuum is $\mathbb{R}P^2$.

hep-th↗
arXiv2008

Geometric variations of the Boltzmann entropy

We perform a calculation of the first and second order infinitesimal variations, with respect to energy, of the Boltzmann entropy of constant energy hypersurfaces of a system with a finite number of degrees of freedom. We comment on the stability interpretation of the second variation in this framework.

cond-mat.stat-mech↗
arXiv2007

Rate of parity violation from measure concentration

We present a geometric argument determining the kinematic (phase-space) factor contributing to the relative rate at which degrees of freedom of one chirality come to dominate over degrees of freedom of opposite chirality, in models with parity violation. We rely on the measure concentration of a subset of a Euclidean cube which is controlled by an isoperimetric inequality. We provide an interpretation of this result in terms of ideas of Statistical Mechanics.

hep-th↗
arXiv2006

The geodesic rule and the spectrum of the vacuum

We analyze the consequences of a recent argument justifying the validity of the "geodesic rule" which can be used to determine the density of global topological defects. We derive a formula that provides a rough estimate of the number of string-like defects formed in a phase transition. We apply this formula to vacua which are spheres. We provide some reasons for the deviation of our predictions from the corresponding accepted values.

hep-th↗
arXiv2006

A stochastic derivation of the geodesic rule

We argue that the geodesic rule, for global defects, is a consequence of the randomness of the values of the Goldstone field $ϕ$ in each causally connected volume. As these volumes collide and coalescence, $ϕ$ evolves by performing a random walk on the vacuum manifold $\mathcal{M}$. We derive a Fokker-Planck equation that describes the continuum limit of this process. Its fundamental solution is the heat kernel on $\mathcal{M}$, whose leading asymptotic behavior establishes the geodesic rule.

hep-th↗
arXiv2005

Algebra and calculus for Tsallis thermostatistics

We construct generalized additions and multiplications, forming fields, and division algebras inspired by the Tsallis thermo-statistics. We also construct derivations and integrations in this spirit. These operations do not reduce to the naively expected ones, when the deformation parameter approaches zero.

cond-mat.stat-mech↗
arXiv2005

Entropy and curvature variations from effective potentials

By using the Jacobi metric of the configuration space, and assuming ergodicity, we calculate the Boltzmann entropy $S$ of a finite-dimensional system around a non-degenerate critical point of its potential energy $V$. We compare $S$ with the entropy of a quantum or thermal system with effective potential $V_{eff}$. We examine conditions, up to first order in perturbation theory, under which these entropies are equal.

math-ph↗