Search results for "Mathematical physics"
showing 10 items of 2687 documents
�ber die Stabilit�t periodischer L�sungen bei zeitabh�ngigen Hamiltonschen Differentialgleichungen von einem Freiheitsgrad
1987
The preservation of certain stable period solutions of the harmonic oscillator under small time-dependent, non-isochronous, and Hamiltonian perturbations is proved.
One-particle Green's function
2013
In this chapter we get acquainted with the one-particle Green's function G , or simply the Green's function. The chapter is divided in three parts. In the first part (Section 6.1) we illustrate what kind of physical information can be extracted from the different Keldysh components of G . The aim of this first part is to introduce some general concepts without being too formal. In the second part (Section 6.2) we calculate the noninteracting Green's function. Finally in the third part (Sections 6.3 and 6.4) we consider the interacting Green's function and derive several exact properties. We also discuss other physical (and measurable) quantities that can be calculated from G and that are re…
Model of compact 3D electromagnetic solitons
2019
Asymptotic structure factor for the two-component Ginzburg-Landau equation
1992
We derive an analytic form for the asymptotic time-dependent structure factor for the two-component Ginzburg-Landau equation in arbitrary dimensions. This form is in reasonable agreement with results from numerical simulations in two dimensions. A striking feature of our analytic form is the absence of Porod's law in the tail. This is a consequence of the continuous symmetry of the Hamiltonian, which inhibits the formation of sharp domain walls.
On the existence of kinetic equations
1974
The existence of the Boltzmann equation and its generalizations is studied by analysing the order of magnitude of their terms. As a consequence we conclude that the reduced distribution functions are not analytic in the density.
Star-products, spectral analysis, and hyperfunctions
2000
We study the ⋆-exponential function U(t;X) of any element X in the affine symplectic Lie algebra of the Moyal ⋆-product on the symplectic manifold (ℝ × ℝ;ω). When X is a compact element, a natural specific candidate for U (t;X) to be the exponential function is suggested by the study we make in the non-compact case. U (t;X) has singularities in the t variable. The analytic continuation U(z;X),z = t + iy, defines two boundary values δ+ U (t;X) = limy↓0 U(z;X) and δ-(t;X) = limy↑0 U(z; X). δ+ U (t;X) is a distribution while δ- U (t;X) is a Beurling-type, Gevrey-class s — 2 ultradistribution. We compute the Fourier transforms in t of δ± U (t;X). Both Fourier spectra are discrete but different …
Finite-size-scaling study of the simple cubic three-state Potts glass: Possible lower critical dimension d=3.
1990
For small lattices with linear dimension L ranging from L=3 to L=8 we obtain the distribution function P(q) of the overlap q between two real replicas of the three-state Potts-glass model with symmetric nearest-neighbor interaction with a Gaussian distribution. A finite-size-scaling analysis suggests a zero-temperature transition to occur with an exponentially diverging correlation length ${\ensuremath{\xi}}_{\mathrm{SG}}$\ensuremath{\sim}exp(C/${\mathit{T}}^{\mathrm{\ensuremath{\sigma}}}$). This implies that d=3 is the lower critical dimension.
Fermion Fields and Their Properties
2011
The fundamental building blocks of matter, i.e. quarks and leptons, carry spin 1/2. There are two formally different but in essence equivalent methods of describing particles with spin: The representation theory of the Poincare group, in the framework of Wigner’s classification hypothesis of particles (see e.g. [QP07], Chap. 6), and the Van der Waerden spinor calculus based on SL(2, \(\mathbb{C}\)).
Kinetics of growth process controlled by convective fluctuations
2001
A model of the spherical (compact) growth process controlled by a fluctuating local convective velocity field of the fluid particles is introduced. It is assumed that the particle velocity fluctuations are purely noisy, Gaussian, of zero mean, and of various correlations: Dirac delta, exponential, and algebraic (power law). It is shown that for a large class of the velocity fluctuations, the long-time asymptotics of the growth kinetics is universal (i.e., it does not depend on the details of the statistics of fluctuations) and displays the power-law time dependence with the classical exponent $1/2$ resembling the diffusion limited growth. For very slow decay of algebraic correlations of flu…