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S. Albeverio

Publications and source records attributed to S. Albeverio.

76 records · Page 5Linked to original sources

Laplace operators in deRham complexes associated with measures on configuration spaces

Let $Γ_X$ denote the space of all locally finite configurations in a complete, stochastically complete, connected, oriented Riemannian manifold $X$, whose volume measure $m$ is infinite. In this paper, we construct and study spaces $L^2_μΩ^n$ of differential $n$-forms over $Γ_X$ that are square integrable with respect to a probability measure $μ$ on $Γ_X$. The measure $μ$ is supposed to satisfy the condition $Σ_m'$ (generalized Mecke identity) well known in the theory of point processes. On $L^2_μΩ^n$, we introduce bilinear forms of Bochner and deRham type. We prove their closabilty and call the generators of the corresponding closures the Bochner and deRham Laplacian, respectively. We prove that both operators contain in their domain the set of all smooth local forms. We show that, under a rather general assumption on the measure $μ$, the space of all Bochner-harmonic $μ$-square integrable forms on $Γ_X$ consists only of the zero form. Finally, a Weitzenböck type formula connecting the Bochner and deRham Laplacians is obtained. As examples, we consider (mixed) Poisson measures, Ruelle type measures on $Γ_{{\Bbb R}^d}$, and Gibbs measures in the low activity--high temperature regime, as well as Gibbs measures with a positive interaction potential on $Γ_X$.

math.PR↗

Many Body Problems with "Spin"-Related Contact Interactions

We study quantum mechanical systems with "spin"-related contact interactions in one dimension. The boundary conditions describing the contact interactions are dependent on the spin states of the particles. In particular we investigate the integrability of $N$-body systems with $δ$-interactions and point spin couplings. Bethe ansatz solutions, bound states and scattering matrices are explicitly given. The cases of generalized separated boundary condition and some Hamiltonian operators corresponding to special spin related boundary conditions are also discussed.

quant-ph↗

An Exactly Solvable Model of Generalized Spin Ladder

A detailed study of an $S={1\over2}$ spin ladder model is given. The ladder consists of plaquettes formed by nearest neighbor rungs with all possible SU(2)-invariant interactions. For properly chosen coupling constants, the model is shown to be integrable in the sense that the quantum Yang-Baxter equation holds and one has an infinite number of conserved quantities. The R-matrix and L-operator associated with the model Hamiltonian are given in a limiting case. It is shown that after a simple transformation, the model can be solved via a Bethe ansatz. The phase diagram of the ground state is exactly derived using the Bethe ansatz equation.

cond-mat↗

Singular Traces and Compact Operators. I

We give a necessary and sufficient condition on a positive compact operator $T$ for the existence of a singular trace (i.e. a trace vanishing on the finite rank operators) which takes a finite non-zero value on $T$. This generalizes previous results by Dixmier and Varga. We also give an explicit description of these traces and associated ergodic states on $\ell^\infty(\Bbb N)$ using tools of non standard analysis in an essential way.

funct-an↗