REVERSE CARLESON MEASURES ON GENERALIZED FOCK SPACES

In this paper,we characterize reverse Carleson measures for a class of generalized Fock spaces F^(p)_(φ),with 0<p<∞and withφsatisfying dd^(c)_(φ)■ω0.As an application of these results,we obtain several equivalent characterizations for invertible Toeplitz operators Tψ,induced by positive bounded symbols φ on F^(2)_(φ).

TOEPLITZ OPERATORS WITH POSITIVE OPERATOR-VALUED SYMBOLS ON VECTOR-VALUED GENERALIZED FOCK SPACES

In this article,we study some characterizations of Toeplitz operators with positive operator-valued function as symbols on the vector-valued generalized Bargmann-Fock spaces Fψ^2.Main results including Fock-Carleson condition,bounded Toeplitz operators,compact Toeplitz operators,and Toeplitz operators in the Schatten-p class are all considered.

Integral Operators Between Fock Spaces

In this paper,the authors study the integral operator■induced by a kernel functionφ(z,·)∈F_α~∞between Fock spaces.For 1≤p≤∞,they prove that S_φ:F_α^(1)→F_α^(p)is bounded if and only if■where k_(a)is the normalized reproducing kernel of F_α^(2);and,S_φ:F_α^(1)→F_α^(p)is compact if and only if■When 1<q≤∞,it is also proved that the condition(?)is not sufficient for boundedness of S_φ:F_α^(q)→F_α^(p).In the particular case■with ■∈F^(2)_α,for 1≤q<p<∞,they show that S_φ:F^(p)_α→F^(q)_αis bounded if and only if■;for 1<p≤q<∞,they give sufficient conditions for the boundedness or compactness of the operator S^(q)_φ:F^(p)_α→F_α.

Block dual Toeplitz Operators on the Orthogonal Complements of Fock Spaces

In this paper,we characterize the boundedness and compactness of the block dual Toeplitz operators acting on the orthogonal complement of the Fock spaces,and the compactness of the finite sum of two dual Toeplitz operators products.The commutator and semi-commutator induced by the block dual Toeplitz operators are considered.

Schatten-p Class(0

In this paper, we discuss the Schatten-p class （0 〈 p≤∞ ） of Toeplitz operators on generalized Foek space with the symbol in positive Borel measure. It makes a great difference from other papers by using the estimates of the kernel and the weight together instead of separately estimating each other. We also get the equivalent conditions when a Toeplitz operator is in the Schatten-p class.

A Note on Weighted Composition Operators on the Fock Space

Based on a new characterization of bounded and compact weighted compositionoperators on the Fock space obtained by Le T （Le T. Normal and isometricweighted composition operators on the Fock space. Bull. London. Math. Soc., 2014,46： 847-856）, this paper shows that a bounded weighted composition operator onthe Fock space is a Fredholm operator if and only if it is an invertible operator, andif and only if it is a nonzero constant multiple of a unitary operator. The result isvery different from the corresponding results on the Hardy space and the Bergmanspace.

Theoretical description of electron-phonon Fock space for gapless and gapped nanowires

We study the effect of electron-phonon （e-ph） interaction on the elastic and inelastic electronic transport of a nanowire connected to two simple rigid leads within the tight-binding and harmonic approximations. The model is constructed using Green＇s function and multi-channel techniques, taking into account the local and nonlocal e-ph interactions. Then, we examine the model for the gapless （simple chain） and gapped （PA-like nanowire） systems. The results show that the tunneling conductance is improved by the e-ph interaction in both local and nonlocal regimes, while for the resonance conductance, the coherent part mainly decreases and the incoherent part increases. At the corresponding energies which depend on the phonon frequency, two dips in the elastic and two peaks in the inelastic conductance spectra appear. The reason is the absorption of the phonon by the electron in transition into inelastic channels.

THE BEREZIN TRANSFORM AND ITS APPLICATIONS

We give a survey on the Berezin transform and its applications in operator theory. The focus is on the Bergman space of the unit disk and the Fock space of the complex plane. The Berezin transform is most effective and most successful in the study of Hankel and Toepltiz operators.

UNBOUNDED COMPLEX SYMMETRIC TOEPLITZ OPERATORS

In this paper,we study unbounded complex symmetric Toeplitz operators on the Hardy space H^(2)(D) and the Fock space g^(2).The technique used to investigate the complex symmetry of unbounded Toeplitz operators is different from that used to investigate the complex symmetry of bounded Toeplitz operators.

THE CODIMENSION FORMULA ON QUASI-INVARIANT SUBSPACES OF THE FOCK SPACE

Let M be an approximately finite codimensional quasi-invariant subspace of the Fock space. This paper gives a formula to calculate the codimension of such spaces and uses this formula to study the structure of quasi-invariant subspaces of the Fock space. Especially, as one of applications, it is showed that the analogue of Beurling's theorem is not true for the Fock space L_a^2 in the case of n > 2.

Ordered product expansions of operators (AB)^±m with arbitrary positive integer

We arrange quantum mechanical operators ■ in their normally ordered product forms by using Touchard polynomials.Moreover,we derive the anti-normally ordered forms of ■ by using special functions as well as Stirling-like numbers together with the general mutual transformation rule between normal and anti-normal orderings of operators.Further,the Q-and P-ordered forms of(QP)±m are also obtained by using an analogy method.

NORM CALCULATIONS OF A CLASS OF INTEGRAL OPERATORS

In this paper we calculate the norm of a special class of integral operators acting on LP （C^n, dvs）, where dvs is the Gaussian measure on C^n.

Commuting Toeplitz Operators on Fock-Sobolev Spaces of Negative Orders

In the setting of Fock-Sobolev spaces of positive orders over the complex plane,Choe and Yang showed that if the one of the symbols of two commuting Toeplitz operators with bounded symbols is non-trivially radial,then the other must also be radial.In this paper,we extend this result to the Fock-Sobolev space of negative order using the Fock-type space with a confluent hyper geometric function.

Analytic Characterization for Hilbert-Schmidt Operators on Fock Space

In this paper we first introduce and investigate some special classes of nonlinear maps and get several useful results. Then, by using these results, we obtain analytic criteria for checking whether or not an operator defined only on the exponential vectors of a symmetric Fock space becomes a Hilbert-Schmidt operator on the whole space. Additionally, as an application, we also get an analytic criterion for Hilbert-Schmidt operators on a Gaussian probability space through the Wiener-Ito-Segal isomorphism.

A Class of Normal Weighted Composition Operators on the Fock Space of C^n

This paper characterizes a class of normal weighted composition operators and their spectrum on the Fock space of Cn.

Sarason’s Toeplitz Product Problem on the Fock–Sobolev Space

The Sarason＇s Toeplitz product problem asks when the Toeplitz product operator TuTv, with analytic symbols u and v, is bounded on Hilbert space of analytic functions. In this paper, we deal with this problem on the Fock-Sobolev space and have a complete solution that u = eq, v = Ce-q, where q is a linear complex polynomial and C is a nonzero constant.

Weighted composition operators on the Fock space

In this paper,we study weighted composition operators on theFock space F^(2).We prove that each bounded composition operator on F^(2) is complex symmetric.This is in sharp contrast with the phenomenon on the Hardy space H^(2)(D).We characterize Hermitian weighted composition operators and algebraic weighted composition operators with degree less than or equal to two on F^(2).In addition,we investigate cyclicity and hypercyclicity of complex symmetric weighted composition operators.We also characterize those weighted compositionoperators that preserveframes,tight frames or normalized tight frames on F^(2).Finally,we study mean ergodicity and uniformly mean ergodicity of weighted composition operators.

Positivity of Fock Toeplitz Operators via the Berezin Transform

Abstract This paper deals with the relationship between the positivity of the Fock Toeplitz operators and their Berezin transforms. The author considers the special case of the bounded radial function φ（z）=α ＋ be-α｜z｜2 ＋ ce-β｜z｜2, where a, b, c are real numbers and α,β are positive numbers. For this type of φ, one can choose these parameters such that the Berezin transform of is a nonnegative function on the complex plane, but the corresponding Toeplitz operator Tφ is not positive on the Fock space.

Characterizations of Bounded Singular Integral Operators on the Fock Space and Their Berezin Transforms

There is a singular integral operators Sj on the Fock space F2(C),which originated from the unitarily equivalent version of the Hilbert transform on L2(R).In this paper,we give an analytic characterization of functions j with finite zeros such that the integral operator Sj is bounded on F2(C)using Hadamard’s factorization theorem.As an application,we obtain a complete characterization for such symbol functions j such that the Berezin transform of Sj is bounded while the operator Sj is not.Also,the corresponding problem in higher dimensions is considered.

On Mathematical Aspects of the Theory of Topological Insulators

This review is devoted to one of the most interesting and actively developing fields in condensed matter physics—theory of topological insulators.Apart from its importance for theoretical physics,this theory enjoys numerous connections with modern mathematics,in particular,with topology and homotopy theory,Clifford algebras,K-theory and non-commutative geometry.From the physical point of view topological invariance is equivalent to adiabatic stability.Topological insulators are characterized by the broad energy gap,stable under small deformations,which motivates application of topological methods.A key role in the study of topological ob jects in the solid state physics is played by their symmetry groups.There are three main types of symmetries—time reversion symmetry,preservation of the number of particles(charge symmetry)and PH-symmetry(particle-hole symmetry).Based on the study of symmetry groups and representation theory of Clifford algebras Kitaev proposed a classification of topological ob jects in solid state physics.In this review we pay special attention to the topological insulators invariant under time reversion.