ARTICLE | doi:10.20944/preprints201910.0171.v1
Subject: Physical Sciences, Optics Keywords: laser cavity; two-level Maxwell-Bloch equations; complex Ginzburg-Landau equation; modulational instability; pattern formation
Online: 16 October 2019 (04:09:00 CEST)
Interaction of an electromagnetic field with matter in a laser cavity without the assumption of a fixed direction of the transverse electric field, described by the two-level Maxwell-Bloch equations, is studied. By using a perturbative nonlinear analysis, performed near the laser threshold, we report on the derivation of the laser (3+1)D vectorial complex cubic-quintic complex Ginzburg-Landau equation. Furthermore, we study the modulational instability of the plane waves both theoretically using the linear stability analysis, and numerically, using direct simulations via the split-step Fourier method. The linear theory predicts instability for any amplitude of the primary waves. Our numerical simulations confirm the theoretical predictions of the linear theory as well as the threshold of the amplitude of perturbations. The system understudy shows a deep dependence on the laser cavity parameters, for which there appear wave patterns in accordance with the predictions from the gain spectrum.
ARTICLE | doi:10.20944/preprints202112.0055.v1
Subject: Physical Sciences, Condensed Matter Physics Keywords: Ginzburg–Landau theory; BCS-BEC crossover; pair fluctuations
Online: 3 December 2021 (13:55:24 CET)
We calculate the parameters of the Ginzburg–Landau (GL) equation of a three-dimensional attractive Fermi gas around the superfluid critical temperature. We compare different levels of approximation throughout the Bardeen–Cooper–Schrieffer (BCS) to the Bose–Einstein Condensate (BEC) regime. We show that the inclusion of Gaussian fluctuations strongly modifies the values of the Ginzburg–Landau parameters approaching the BEC regime of the crossover. We investigate the reliability of the Ginzburg–Landau theory, with fluctuations, studying the behavior of the coherence length and of the critical rotational frequencies throughout the BCS-BEC crossover. The effect of the Gaussian fluctuations gives qualitative correct trends of the considered physical quantities from the BCS regime up to the unitary limit of the BCS-BEC crossover. Approaching the BEC regime, the Ginzburg–Landau equation with the inclusion of Gaussian fluctuations turns out to be unreliable.
ARTICLE | doi:10.20944/preprints202210.0091.v9
Subject: Mathematics & Computer Science, Applied Mathematics Keywords: Duality principles; Generalized method of lines; Ginzburg-Landau type equations
Online: 20 December 2022 (02:32:43 CET)
This article develops dual variational formulations for a large class of models in variational optimization. The results are established through basic tools of functional analysis, convex analysis and duality theory. The main duality principle is developed as an application to a Ginzburg-Landau type system in superconductivity in the absence of a magnetic field. In the first sections, we develop new general dual convex variational formulations, more specifically, dual formulations with a large region of convexity around the critical points which are suitable for the non-convex optimization for a large class of models in physics and engineering. Finally, in the last section we present some numerical results concerning the generalized method of lines applied to a Ginzburg-Landau type equation.
ARTICLE | doi:10.20944/preprints202210.0207.v9
Subject: Mathematics & Computer Science, Applied Mathematics Keywords: convex dual variational formulation; duality principle for non-convex local primal optimization; Ginzburg-Landau type equation
Online: 24 November 2022 (14:33:34 CET)
This article develops duality principles and related convex dual formulations suitable for the local optimization of non-convex primal formulations for a large class of models in physics and engineering. The results are based on standard tools of functional analysis, calculus of variations and duality theory. In particular, we develop applications to a Ginzburg-Landau type equation.
Subject: Physical Sciences, Particle & Field Physics Keywords: Complex Dynamics; Ginzburg-Landau (GL) equation; Chaos and Bifurcations; Multifractals; Self-organized Criticality (SOC); Minimal Fractal Manifold; Fractional Field Theory
Online: 9 November 2020 (08:38:02 CET)
This work is a top-level summary of several contributions published in the last three decades. It makes the case that complex dynamics of nonlinear systems lies at the heart of foundational physics.
ARTICLE | doi:10.20944/preprints201901.0295.v1
Subject: Physical Sciences, Condensed Matter Physics Keywords: topological insulator; phase transition; mercury cadmium telluride; Landau levels; magneto-absorption; magnetotransport
Online: 29 January 2019 (16:44:14 CET)
We report on comparison between temperature-dependent magneto¬absorption and magnetotransport spectroscopy of HgTe/CdHgTe quantum wells in terms of detection of phase transition between topological insulator and band insulator states. Our results demonstrate that temperature-dependent magnetospectroscopy is a powerful tool to discriminate trivial and topological insulator phases, yet magnetotransport method is shown to have advantages for clear manifestation of the phase transition with accurate quantitative values of transition parameter (i.e. critical magnetic field Bc).
ARTICLE | doi:10.20944/preprints201811.0345.v1
Subject: Physical Sciences, Fluids & Plasmas Keywords: Landau damping; resonant transfer; anharmonic lattice; nonlinear waves; collective modes; gravity waves; Stokes flow; Basset drag force; surfactant approximation; fractional derivative; anharmonic
Online: 15 November 2018 (05:43:52 CET)
The Landau damping effect was observed in collisionless plasma, as a microscopic resonant mechanism between electromagnetic radiation and the collective modes. In this paper we demonstrate the occurrence of the Landau damping at macroscopic scale in the interaction between water waves and anharmonic lattice of magnetic buoys. By coupling the Navier-Stokes equations for incompressible fluid with the nonlinear dynamics of an anharmonic magnetic lattice we obtain a resonant transfer of momentum and energy between the two systems. The velocity of the flow is obtained in the Stokes approximation with Basset type of drag force. The dynamics of the buoys is calculated in the surfactant approximation for a specific frequency, then we use Fourier analysis to obtain the general time variable interaction. After involving an integral Dirichlet transform we obtain the time dependent expression of the drag force, the interaction waves-lattice with a new term in the form of a Caputo fractional derivative. We compare the results of the model with experiments performed in a wave tank with free floating magnetic buoys under the action of small amplitude gravitational waves. This configuration can be applied in studies for the attenuation with resonant damping of rogue waves, storms or tsunamis.
ARTICLE | doi:10.20944/preprints202006.0365.v2
Subject: Mathematics & Computer Science, Algebra & Number Theory Keywords: Cramer`s conjecture; distribution of primes; elementary proof of the Riemann's Hypothesis; Landau problems; Legendre conjecture; Littlewood`s proof of 1914; logarithmic integral; maximal prime gaps; Prime Number Theorem; Tailored logarithmic integral; prime counting function Supremum; prime counting function Infimum.
Online: 6 July 2021 (11:32:03 CEST)
This research paper aims to explicate the complex issue of the Riemann's Hypothesis and ultimately presents its elementary proof. The method implements one of the binomial coefficients, to demonstrate the maximal prime gaps bound. Maximal prime gaps bound constitutes a comprehensive improvement over the Bertrand's result, and becomes one of the key elements of the theory. Subsequently, implementing the theory of the primorial function and its error bounds, an improved version of the Gauss' offset logarithmic integral is developed. This integral serves as a Supremum bound of the prime counting function Pi(n). Due to its very high precision, it permits to verify the relationship between the prime counting function Pi(n) and the offset logarithmic integral of Carl Gauss. The collective mathematical theory, via the Niels F. Helge von Koch equation, enables to prove the RIemann's Hypothesis conclusively.