Quasi-Sectorial Contractions (2008)
We revise the notion of the quasi-sectorial contractions. Our main theorem establishes a relation between semigroups of quasi-sectorial contractions and a class of m−sectorial generators. We...
Potential approximations to 0: an inverse Klauder (2007)
Pavel Exner, Hagen Neidhardt, Valentin A. Zagrebnov
a;b
Universit de la Mditerrane (Aix-Marseille II) (2007)
Takashi Ichinose, Hagen Neidhardt, Valentin A. Zagrebnov
product formula and fractional powers of self-adjoint generators
1 Allocataire-moniteur at Universit'e de la M'editerran'ee (Aix-Marseille II) (2007)
For Nonself-adjoint, Gibbs Semigroups, Vincent Cachia, Valentin A. Zagrebnov, Cnrs Luminy
We prove the trace-norm convergence of the Trotter product formula for nonselfadjoint Gibbs semigroups. For any m-sectorial generators A and B such that e \GammatRe A is in the trace-class for t? 0,...
Vincent Cachia, Hagen Neidhardt, Valentin A. Zagrebnov
Let A be a positive self-adjoint operator and let B be an m-accretive operator which is A-small with a relative bound less than one. Let H = A+B, then H is well-defined on dom(H) = dom(A) and...
Linear non-autonomous Cauchy problems and evolution semigroups (2007)
Neidhardt, Hagen, Zagrebnov, Valentin A.
The paper is devoted to the problem of existence of propagators for an abstract linear non-autonomous evolution Cauchy problem of hyperbolic type in separable Banach spaces. The problem is solved...
The effect of time-dependent coupling on non-equilibrium steady states (2007)
Cornean, Horia D., Neidhardt, Hagen, Zagrebnov, Valentin A.
Consider (for simplicity) two one-dimensional semi-infinite leads coupled to a quantum well via time dependent point interactions. In the remote past the system is decoupled, and each of its...
Models for Equilibrium BEC Superradiance (2007)
Pule, Joseph V., Verbeure, Andre, Zagrebnov, Valentin A.
Motivated by recent experiments with superradiant Bose-Einstein Condensate (BEC) we consider simple microscopic models describing rigorously the interference of the two cooperative phenomena, BEC and...
The Canonical Perfect Bose Gas in Casimir Boxes (2007)
Pule, Joseph V., Zagrebnov, Valentin A.
We study the problem of Bose-Einstein condensation in the perfect Bose gas in the canonical ensemble, in anisotropically dilated rectangular parallelpipeds (Casimir boxes). We prove that in the...
Zeno product formula revisited (2007)
Exner, Pavel, Ichinose, Takashi, Neidhardt, Hagen, Zagrebnov, Valentin A.
We introduce a new product formula which combines an orthogonal projection with a complex function of a non-negative operator. Under certain assumptions on the complex function the strong convergence...
The Approximating Hamiltonian Method for the Imperfect Boson Gas (2007)
Pule, Joseph V., Zagrebnov, Valentin A.
The pressure for the Imperfect (Mean Field) Boson gas can be derived in several ways. The aim of the present note is to provide a new method based on the Approximating Hamiltonian argument which is...
Université de laMéditerranée (Aix-Marseille II) Centre de Physique Théorique- UMR 6207 (2007)
Hagen Neidhardt, Valentin A. Zagrebnov
The paper is devoted to the problem of existence of propagators for an abstract linear non-autonomous evolution Cauchy problem of hyperbolic type in separable Banach spaces. The problem is solved...
Rebenko, Alexei L., Zagrebnov, Valentin A.
We construct the Gibbs state for $\nu$-dimensional quantum crystal with site displacements from $\R^d$, $d\geq 1$, and with a one-site \textit{non-polynomial} double-well potential, which has...
Zeno product formula revisited (2004)
Exner, Pavel, Ichinose, Takashi, Neidhardt, Hagen, Zagrebnov, Valentin A.
We introduce a new product formula which combines an orthogonal projection with a complex function of a non-negative operator. Under certain assumptions on the complex function the strong convergence...
Models with Recoil for Bose-Einstein Condensation and Superradiance (2004)
Pulé, Joseph V., Verbeure, André F., Zagrebnov, Valentin A.
In this paper we consider two models which exhibit equilibrium BEC superradiance. They are related to two different types of superradiant scattering observed in recent experiments. The first one...
A Dicke Type Model for Equilibrium BEC Superradiance (2004)
Pule, Joseph V., Verbeure, Andre F., Zagrebnov, Valentin A.
We study the effect of electromagnetic radiation on the condensate of a Bose gas. In an earlier paper we considered the problem for two simple models showing the cooperative effect between...
Bose-Einstein Condensation in Geometrically Deformed Tubes (2004)
Exner, Pavel, Zagrebnov, Valentin A.
We show that Bose-Einstein condensate can be created in quasi-one-dimensional systems in a purely geometrical way, namely by bending or other suitable deformation of a tube.
Rebenko, Alexei L., Zagrebnov, Valentin A.
We construct the Gibbs state for $\nu$-dimensional quantum crystal with site displacements from $\R^d$, $d\geq 1$, and with a one-site \textit{non-polynomial} double-well potential, which has...
Models for Equilibrium BEC Superradiance (2004)
Pule, Joseph V., Verbeure, Andre, Zagrebnov, Valentin A.
Motivated by recent experiments with superradiant Bose-Einstein Condensate (BEC) we consider simple microscopic models describing rigorously the interference of the two cooperative phenomena, BEC and...
The Canonical Perfect Bose Gas in Casimir Boxes (2004)
Pule, Joseph V., Zagrebnov, Valentin A.
We study the problem of Bose-Einstein condensation in the perfect Bose gas in the canonical ensemble, in anisotropically dilated rectangular parallelpipeds (Casimir boxes). We prove that in the...
The Approximating Hamiltonian Method for the Imperfect Boson Gas (2004)
Pule, Joseph V., Zagrebnov, Valentin A.
The pressure for the Imperfect (Mean Field) Boson gas can be derived in several ways. The aim of the present note is to provide a new method based on the Approximating Hamiltonian argument which is...
Discontinuity of the magnetization in diluted O(n)-models (2000)
Lincoln Chayes, Senya B. Shlosman, Valentin A. Zagrebnov
We study the annealed site-diluted versions of the classical O(n) Heisenberg ferromagnets. It is shown that if the temperature is low enough, then at some value of the chemical potential there is...