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At least 127 records · Page 7Linked to original sources
arXiv2008

Riemann-Hilbert problem associated to Frobenius manifold structures on Hurwitz spaces: irregular singularity

Solutions to the Riemann-Hilbert problems with irregular singularities naturally associated to semisimple Frobenius manifold structures on Hurwitz spaces (moduli spaces of meromorphic functions on Riemann surfaces) are constructed. The solutions are given in terms of meromorphic bidifferentials defined on the underlying Riemann surface. The relationship between different classes of Frobenius manifold structures on Hurwitz spaces (real doubles, deformations) is described on the level of the corresponding Riemann-Hilbert problems.

math-ph↗
arXiv2012

Self-adjoint, globally defined Hamiltonian operators for systems with boundaries

For a general self-adjoint Hamiltonian operator $H_0$ on the Hilbert space $L^2(\RE^d)$, we determine the set of all self-adjoint Hamiltonians $H$ on $L^2(\RE^d)$ that dynamically confine the system to an open set $Ω\subset \RE^d$ while reproducing the action of $ H_0$ on an appropriate operator domain. In the case $H_0=-Δ+V$ we construct these Hamiltonians explicitly showing that they can be written in the form $H=H_0+ B$, where $B$ is a singular boundary potential and $H$ is self-adjoint on its maximal domain. An application to the deformation quantization of one-dimensional systems with boundaries is also presented.

math-ph↗
arXiv2007

On Some New Proof of the Bogoliubov-Parasiuk Theorem (Nonequilibrium Renormalization Theory II)

It is usually used a complicated combinatorics to prove the Bogoliubov-Parasiuk theorem. In the present paper we give a proof of the Bogoliubov-Parasiuk theorem which use a simple combinatorics. To give this proof we interpret Feynman amplitudes as distributions on the space of α-parameters. We will use this technique in the next paper to give a proof that the divergences in nonequilibrium diagram technique can be subtracted by means the counterterms of asymptotical state.

math-ph↗
arXiv2008

Quantum Cohomology and Crepant Resolutions: A Conjecture

We give an expository account of a conjecture, developed by Coates--Corti--Iritani--Tseng and Ruan, which relates the quantum cohomology of a Gorenstein orbifold X to the quantum cohomology of a crepant resolution Y of X. We explore some consequences of this conjecture, showing that it implies versions of both the Cohomological Crepant Resolution Conjecture and of the Crepant Resolution Conjectures of Ruan and Bryan--Graber. We also give a "quantized" version of the conjecture, which determines higher-genus Gromov--Witten invariants of X from those of Y.

math.AG↗
arXiv2007

Stability of peakons for the Degasperis-Procesi equation

The Degasperis-Procesi equation can be derived as a member of a one-parameter family of asymptotic shallow water approximations to the Euler equations with the same asymptotic accuracy as that of the Camassa-Holm equation. In this paper, we study the orbital stability problem of the peaked solitons to the Degasperis-Procesi equation on the line. By constructing a Liapunov function, we prove that the shapes of these peakon solitons are stable under small perturbations.

math.AP↗
arXiv2013

On the Self-Recovery Phenomenon in the Process of Diffusion

We report a new phenomenon, called self-recovery, in the process of diffusion in a region with boundary. Suppose that a diffusing quantity is uniformly distributed initially and then gets excited by the change in the boundary values over a time interval. When the boundary values return to their initial values and stop varying afterwards, the value of a physical quantity related to the diffusion automatically comes back to its original value. This self-recovery phenomenon has been discovered and fairly well understood for finite-dimensional mechanical systems with viscous damping. In this paper, we show that it also occurs in the process of diffusion. Several examples are provided from fluid flows, quasi-static electromagnetic fields and heat conduction. In particular, our result in fluid flows provides a dynamic explanation for the famous experiment by Sir G.I. Taylor with glycerine in an annulus on kinematic reversibility of low-Reynolds-number flows.

physics.flu-dyn↗
arXiv2013

Large eddy simulation of a muffler with the high-order spectral difference method

The combination of the high-order accurate spectral difference discretization on unstructured grids with subgrid-scale modelling is investigated for large eddy simulation of a muffler at Re = 4.64 10^4 and low Mach number. The subgrid-scale stress tensor is modelled by the wall-adapting local eddy-viscosity model with a cut-off length which is a decreasing function of the order of accuracy of the scheme. Numerical results indicate that although the high-order solver without subgrid-scale modelling is already able to capture well the features of the flow, the coupling with the wall-adapting local eddy-viscosity model improves the quality of the solution.

physics.flu-dyn↗
arXiv2013

Josephson effect and slow-fast systems

In order to model the processes taking place in systems with Josephson contacts, a differential equation on a torus with three parameters is used. One of the parameters of the system can be considered small and the methods of the fast--slow systems theory can be applied. The properties of the phase--lock areas -- the subsets in the parameter space, in which the changing of a current doesn't affect the voltage -- are important in practical applications. The phase-lock areas coincide with the Arnold tongues of a Poincare map along the period. A description of the limit properties of Arnold tongues is given. It is shown that the parameter space is split into certain areas, where the tongues have different geometrical structures due to fast--slow effects. An efficient algorithm for the calculation of tongue borders is elaborated. The statement concerning the asymptotic approximation of borders by Bessel functions is proven.

math.DS↗
arXiv2013

A Reproducing Kernel and Toeplitz Operators in the Quantum Plane

We define and analyze Toeplitz operators whose symbols are the elements of the complex quantum plane, a non-commutative, infinite dimensional algebra. In particular, the symbols do not come from an algebra of functions. The process of forming operators from non-commuting symbols can be considered as a second quantization. To do this we construct a reproducing kernel associated with the quantum plane. We also discuss the commutation relations of creation and annihilation operators which are defined as Toeplitz operators. This paper extends results of the author for the finite dimensional case.

math-ph↗
arXiv2013

Solution of W-Constraints for R-Spin Intersection Numbers

We present a solution to the W-constraints satisfied by the intersection numbers on the moduli spaces of r-spin curves. We make use of a grading suggested by the selection rule for the correlators determined by the geometry of the moduli space.

math-ph↗
arXiv2013

On retardation, radiation and Liénard-Wiechert type potentials in electrodynamics and elastodynamics

The aim of this paper is to investigate the fundamental problems of retardation and radiation caused by non-uniformly moving point sources using the theories of electrodynamics and elastodynamics. This paper investigates and compares the retarded electromagnetic fields and the retarded elastodynamic fields. For the non-uniform motion of a general point source, the Liénard-Wiechert type potentials and the radiation and nonradiation fields are derived for a point charge and for a point force.

physics.class-ph↗
arXiv2013

Resonant effects in random dielectric structures

Recently, a theory for artificial magnetism in two-dimensional photonic crystals has been developed for large wavelength using homogenization techniques. In this paper we pursue this approach within a rigorous stochastic framework: dielectric parallel nanorods are randomly disposed, each of them having, up to a large scaling factor, a random permittivity ε(ω) whose law is represented by a density on a window Δ=[a,b]x[0,h] of the complex plane. We give precise conditions on the initial probability law (permittivity, radius and position of the rods) under which the homogenization process can be performed leading to a deterministic dispersion law for the effective permeability with possibly negative real part. Subsequently a limit analysis h->0, accounting a density law of ε, which concentrates on the real axis, reveals singular behavior due to the presence of resonances in the microstructure.

math-ph↗
arXiv2013

On generalized Volterra systems

We construct a large family of evidently integrable Hamiltonian systems which are generalizations of the KM system. The Hamiltonian vector field is homogeneous cubic but in a number of cases a simple change of variables transforms such a system to a quadratic Lotka-Volterra system. We present in detail all such systems in dimensions 4 and 5 and we also give some examples from higher dimensions. This construction generalizes easily to each complex simple Lie algebra.

math-ph↗
arXiv2013

Gauss-Seed Nets of Sturm-Liouville Problems With Energy-Independent Characteristic Exponents and Related Sequences of Exceptional Orthogonal Polynomials I. Canonical Darboux Transformations Using AEH Functions

The paper applies the so-called 'Canonical-Darboux-Transformation' (CDT) method to reproduce general expressions for rational potentials (RPs) quantized in terms of exceptional orthogonal polynomial systems (X-OPSs). The benchmark of the new method recently developed by the author for implicit potentials solvable via hypergeometric functions is that rationally-extended SUSY partners of the original potential are quantized in terms of sequences of the so-called 'Gauss-seed' (GS) Heine polynomials starting from a polynomial of non-zero order. The common mark of the Darboux-Poschl-Teller (DPT) potential and isotonic oscillator discussed in this paper is that the appropriate rational Sturm-Liouville (RSL) equations have energy-independent characteristic exponents at both singular end points and as a result the appropriate sequences of GS Heine polynomials turn into X-OPSs with infinitely many members.

math-ph↗
arXiv2013

An integrable evolution equation in geometry

We introduce an integrable Hamiltonian system which Lax deforms the Dirac operator D=d+d* on a finite simple graph or compact Riemannian manifold. We show that the nonlinear isospectral deformation always leads to an expansion of the original space, featuring a fast inflationary start. The nonlinear evolution leaves the Laplacian L=D^2 invariant so that linear Schroedinger or wave dynamics is not affected. The expansion has the following effects: a complex structure can develop and the nonlinear quantum mechanics asymptotically becomes the linear relativistic Dirac wave equation u''=Lu. While the later is not aware of the expansion of space and does not see the emerged complex structure, nor the larger non-commutative geometric setup, the nonlinear flow is affected by it. The natural Noether symmetries of quantum mechanics introduced here force to consider space as part of a larger complex geometry. The nonlinear evolution equation is a symmetry of quantum mechanics which still features super-symmetry, but it becomes clear why it is invisible: while the McKean-Singer formulas str(exp(i D(t) t)) = str(exp(-L t))=chi(G) still hold, the super-partners f,Df are orthogonal only at t=0 and become parallel or anti-parallel for |t| to infinity.

math.DS↗
arXiv2013

Propagators in two-dimensional lattices

This paper is devoted to the computation of discrete propagators in two-dimensional crystals and their application to a number of time dependent problems. The methods to compute such kernels are provided by a tight-binding representation of Dirac matrices and the generalizations of Bessel functions. Diffusive effects of point-like distributions on crystalline sheets are studied in a second quantization scheme. In the last part, a compendium of propagators is presented. The cases of square, triangular and hexagonal arrays are covered.

quant-ph↗