Andreev states in a quasi-one-dimensional superconductor on the surface of a topological insulator

Theoretical and Mathematical Physics - We study bound states in an s-wave superconducting strip on the surface of a topological superconductor with the perpendicular Zeeman field. We prove...     

Mutual transition of Andreev and Majorana bound states in a superconducting gap

Theoretical and Mathematical Physics - Using the Bogoliubov–de Gennes Hamiltonian, we analytically study two models with superconducting order, the p-wave model with an impurity potential and...     

Quarks confinement via Kaluza–Klein theory as a topological property of quantum classical spacetime phase transition

By introducing a curled fifth dimension, Kaluza–Klein theory predicted for the first time a connection between gravity and electromagnetism. An exacting look at this result shows that for a radius R of the fifth dimension equal to the Planck length, the coupling is exactly unity. The result is utilized to show that by introducing correction terms to the one loop renormalization equation of unification it can be made exact and subsequently quark confinement can be proven non-perturbatively as a property of the topology of quantum spacetime at the classical-quantum interface and the Planck phase transition.     

High-energy solutions for a phase transition problem

In this article we study the existence and profile of high-energy solutions for the phase transition model

     

Computing mountain passes and transition states

The mountain-pass theorem guarantees the existence of a critical point on a path that connects two points separated by a sufficiently high barrier. We propose the elastic string algorithm for computing mountain passes in finite-dimensional problems and analyze the convergence properties and numerical performance of this algorithm for benchmark problems in chemistry and discretizations of infinite-dimensional variational problems. We show that any limit point of the elastic string algorithm is a path that crosses a critical point at which the Hessian matrix is not positive definite.This work was supported by the Mathematical, Information, and Computational Sciences Division subprogram of the Office of Advanced Scientific Computing Research, Office of Science, U.S. Department of Energy, under Contract W-31-109-Eng-38.     

A phase transition for the coupled branching process

Summary We consider a particular Markov process _t ^u on ^S ,S= ⁿ . The random variable _t ^u (x) is interpreted as the number of particles atx at timet. The initial distribution of this process is a translation invariant measure withf(x)d<. The evolution is as follows: At rateb(x) a particle is born atx but moves instantaneously toy chosen with probabilityq(x, y). All particles at a site die at ratepd withp[0, 1],d, ⁺ and individual particles die independently from each other at rate (1–p)d. Every particle moves independently of everything else according to a continuous time random walk.We are mainly interested in the caseb=d andn3. The process exhibits a phase transition with respect to the parameterp: Forp<p ^* all weak limit points of ( _t ^µ ) ast still have particle density (x)d. Forp>p ^*, _t ^µ ) converges ast to the measure concentrated on the configuration identically 0. We calculatep ^* as well asp ⁽ⁿ⁾ , the points with the property that the extremal invariant measures have forp>p ⁽ⁿ⁾ infiniten-th moment of (x) and forp<p ⁽ⁿ⁾ finiten-th moment. We show the case 1>p ^*>p⁽²⁾>p⁽³⁾...p ⁽ⁿ⁾ >0, p⁽ⁿ⁾0 occurs for suitable values of the other parameters. Forp<p ⁽²⁾ we prove the system has a one parameter set of extremal invariant measures and we determine their domain of attraction. Part I contains statements of all results but only the proofs of the results about the process for values ofp withp<p ⁽²⁾ and the behaviour of then-th moments andp ⁽ⁿ⁾ .     

Sharp phase transition theorems for hyperbolicity of random groups

We prove that in various natural models of a random quotient of a group, depending on a density parameter, for each hyperbolic group there is some critical density under which a random quotient is still hyperbolic with high probability, whereas above this critical value a random quotient is very probably trivial. We give explicit characterizations of these critical densities for the various models.     

On a phase transition model

An Allen–Cahn phase transition model with a periodic nonautonomous term is presented for which an infinite number of transition states is shown to exist. A constrained minimization argument and the analysis of a limit problem are employed to get states having a finite number of transitions. A priori bounds and an approximation procedure give the general case. Decay properties are also studied and a sharp transition result with an arbitrary interface is proved.     

Principal eigenvalues,topological pressure,and stochastic stability of equilibrium states

Suppose thatL is a second order elliptic differential operator on a manifoldM, B is a vector field, andV is a continuous function. The paper studies by probabilistic and dynamical systems means the behavior asɛ → 0 of the principal eigenvalueλ ^ε (V) for the operatorL ^ε = ɛL + (B, ∇) +V considered on a compact manifold or in a bounded domain with zero boundary conditions. Under certain hyperbolicity conditions on invariant sets of the dynamical system generated by the vector fieldB the limit asɛ → 0 of this principal eigenvalue turns out to be the topological pressure for some function. This gives a natural transition asɛ → 0 from Donsker-Varadhan’s variational formula for principal eigenvalues to the variational principle for the topological pressure and unifies previously separate results on random perturbations of dynamical systems. This work was supported by US-Israel Binational Science Foundation.     

Calculation of Berry's phase in squeezed states

A simple method based on generalized coherent states is proposed for calculation of Berry's phase. In this paper we calculate Berry's phase for a translated oscillator in standard coherent states as well as Berry's phase in squeezed states and spin coherent states, i.e., coherent states for the SU(1, 1) and SU(2) groups, respectively.Translated from Zapiski Nauchnykh Seminarov Leningradskogo Otdeleniya Matematicheskogo Instituta im. V. A. Steklova AN SSSR, Vol. 169, pp. 51–59, 1988.     

Turbulence as a nonequilibrium phase transition

The transition from laminar to turbulent flow is studied on the basis of an exact equation for the averaged velocity and an approximate nonlinear equation for the Reynolds stress . The stationary state can be determined from the condition of minimum of a functional that is analogous to the Landau functional in the theory of phase transitions. The Reynolds stress plays the role of a parameter. It is shown that a nontrivial solution for corresponding to a steady turbulent regime exists only for Reynolds numbersR that exceed a certain critical valueR _cr. The results of a numerical calculation of the profile of the averaged velocity, the friction coefficient, and the Reynolds stress in a wide range of values ofR agree well with experimental data for channel flow.V. A. Steklov Mathematics Institute, Russian Academy of Sciences. Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 92, No. 2, pp. 293–311, August, 1992.     

QGP phase transition and multiplicity fluctuations

The scaled factorial moments in QGP phase transitions are studied analytically by the extended Ginzburg-Landau model. The dependence of lnF _q on phase space interval is different for the first- and second-order QGP phase transitions. When lnF _q, are fitted to polynomials ofX≡δ^1/3, the relative sign between the fitted coefficients ofX andb _q,1 calculated theoretically can be used to judge the order of phase transitions. Two sets of experimental data are reanalysed and the phase transitions are the first order for one set of data but the second order for another.     

Regularity in parabolic phase transition problems

We describe the main results obtained in a joint work with Athanasopoulos and Caffarelli on the regularity of viscosity solutions and of their free boundaries for a rather general class of parabolic phase transition problems. To a great unforgettable Master.