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Diana Barseghyan

Publications and source records attributed to Diana Barseghyan.

At least 19 recordsLinked to original sources

Intrinsic {Right} $q$-Radial Vector Derivatives and Localized Fischer Decompositions on Radial Algebras

We define intrinsic right \(q\)-radial vector derivatives on radial algebras of abstract vector variables. For a finite parameter set \(Y\), a scalar Jackson calculus on \(x^2\) and the mixed anticommutators \(\{x,y_i\}\) is combined with the exterior decomposition relative to \(x\). Relabelling covariance and compatibility under inclusions of parameter sets give a direct-limit operator on arbitrary radial algebras. {Under the dimension specialization \(Q=q^M\), its classical limit agrees in every \(M\)-dimensional Clifford realization with the standard right Clifford derivative; for an exterior blade one obtains \([x\wedge y_I]\partial_x=(-1)^{|I|}(M-|I|)y_I\).} Two Fischer-type constructions are considered. The anticommutator with exterior creation is triangular and admits an explicit Green inverse after localization at its diagonal factors. {For right \(q\)-monogenic elements, the derivative is paired with right multiplication \(R_xF=Fx\). The homogeneous operators \(\partial^{Y,\mathrm R}_{x,q}R_x\) have generically nonzero determinants, which yields determinant-localized Fischer decompositions and explicit projectors.} The one- and two-vector determinants are computed explicitly. {After \(Q=q^M\), the two-vector determinant is nonzero for every \(0<q<1\) and every positive integer \(M\). For arbitrary finite support, a support filtration factors the determinant into exact-support terms; in degree zero, support rank \(p\) contributes the factor \([m-p]_q+p\).}

math.CV↗

Spectral properties of the magnetic Robin Laplacian on curvilinear half-plane

We analyse magnetic Robin Laplacian in curvilinear half-plane with a smooth boundary. It is well known that the spectrum of the Robin Laplacian is unstable with respect to boundary deformations. This means that if the boundary is a straight line then the spectrum of the Robin Laplacian is purely essential. From the other hand, the perturbation of the boundary produces eigenvalues below the essential spectrum. In this paper, the Robin-Laplace operator with a compactly supported magnetic field is considered. We prove that the spectrum of the magnetic Robin Laplacian is stable under small and local deformations of the boundary.

math.SP↗

Magnetic Dirichlet Laplacian on deformed waveguides

It is well known that the spectrum of the Dirichlet Laplacian for a two-dimensional waveguide, which is a local deformation of a straight strip, is unstable with respect to waveguide boundary deformations. This means that, when the waveguide is a straight strip, the spectrum of the Dirichlet Laplacian is purely essential. On the other hand, local boundary perturbations of the straight strip produce eigenvalues below the essential spectrum. This paper considers the Dirichlet-Laplace operator with a compactly supported magnetic field. Furthermore, we omit the condition that the boundary perturbation is local. We prove that, in this case, the spectrum of the magnetic Laplacian is stable under small deformations of the waveguide boundary.

math.SP↗

Magnetic Dirichlet Laplacian on a perturbed twisted tube

It is well known that the spectrum of the Dirichlet Laplacian for a compact perturbation of a three-dimensional, periodically twisted tube is unstable with respect to domain deformations. This means that if the periodically twisted tube is unperturbed, then the spectrum of the Dirichlet Laplacian is purely essential. On the other hand, the perturbation of this domain produces eigenvalues below the essential spectrum. This paper considers the Dirichlet-Laplace operator with a magnetic field. We explicitly prove that the spectrum of the magnetic Laplacian is stable under small and local deformations of the domain.

math.SP↗

Three-dimensional magnetic Schrödinger operator with the potential supported in a tube

In this paper, we study the following magnetic Schrödinger operator in $\mathbb{R}^3$: \[ H=(i \nabla +A)^2- \tilde{V}, \] where $\tilde{V}$ is non-negative potential supported over the tube built along a curve which is a local deformation of a straight one, and $B:=\mathrm{rot}(A)$ is a non-zero and local (i.e., a compact supported) magnetic field. Based on some new strategies, we first prove that the magnetic field does not change the essential spectrum of this system. Finally, in the last section of this paper, we establish the sufficient condition such that the discrete spectrum is empty.

math.SP↗

Magnetic Dirichlet Laplacian in curved waveguides

For a two-dimensional curved waveguide, it is well known that the spectrum of the Dirichlet Laplacian is unstable. Any perturbation of the straight strip produces eigenvalues below the essential spectrum. In this paper, a magnetic field is added. We explicitly prove that the spectrum of the magnetic Laplacian is stable under small but non-local deformations of the waveguide.

math.SP↗

Spectral convergence of the Laplace operator with Robin boundary conditions on a small hole

In this paper we study a bounded domain with a small hole removed. Our main result concerns the spectrum of the Laplace operator with the Robin conditions imposed at the hole boundary. Moreover we prove that under some suitable assumptions on the parameter in the boundary condition the spectrum of the Laplacian converges in the Hausdorff distance sense to the spectrum of the Laplacian defined on the unperturbed domain.

math.SP↗

Magnetic Neumann Laplacian on a domain with hole

This article gives a domain with a small compact set of removed and the magnetic Neumann Laplacian on such set. The main theorem of this article shows the description of the holes which do not change the spectrum drastically. In this article we prove that the spectrum of the magnetic Neumann Laplacian converges in the Hausdorff distance sense to the spectrum of the original operator defined on the unperturbed domain.

math.SP↗

Neumann Laplacian in a perturbed domain

We consider a domain with a small compact set of zero Lebesgue measure of removed. Our main result concerns the spectrum of the Neumann Laplacian defined on such domain. We prove that the spectrum of the Laplacian converges in the Hausdorff distance sense to the spectrum of the Laplacian defined on the unperturbed domain.

math.SP↗

Magnetic field influence on the discrete spectrum of locally deformed leaky wires

We consider magnetic Schrödinger operator $H=(i \nabla +A)^2-αδ_Γ$ with an attractive singular interaction supported by a piecewise smooth curve $Γ$ being a local deformation of a straight line. The magnetic field $B$ is supposed to be nonzero and local. We show that the essential spectrum is $[-\frac14α^2,\infty)$, as for the non-magnetic operator with a straight $Γ$, and demonstrate a sufficient condition for the discrete spectrum of $H$ to be empty.

math.SP↗

Eigenvalue bound for Schroedinger operators with unbounded magnetic field

In this paper we consider magnetic Schroedinger operators on the two-dimensional unit disk with a radially symmetric magnetic field which explodes to infinity at the boundary. We prove a bound for the eigenvalue moments and a bound for the number of negative eigenvalues for such operators.

math.SP↗

Spectral estimates for Dirichlet Laplacian on tubes with exploding twisting velocity

We study the spectrum of the Dirichlet Laplacian on an unbounded twisted tube with twisting velocity exploding to infinity. If the tube cross section does not intersect the axis of rotation, then its spectrum is purely discrete under some additional conditions on the twisting velocity (D.Krejcirik, 2015). In the current work we prove a Berezin type upper bound for the eigenvalue moments.

math.SP↗

Spectral geometry in a rotating frame: properties of the ground state

We investigate spectral properties of the operator describing a quantum particle confined to a planar domain $Ω$ rotating around a fixed point with an angular velocity $ω$ and demonstrate several properties of its principal eigenvalue $λ_1^ω$. We show that as a function of rotating center position it attains a unique maximum and has no other extrema provided the said position is unrestricted. Furthermore, we show that as a function $ω$, the eigenvalue attains a maximum at $ω=0$, unique unless $Ω$ has a full rotational symmetry. Finally, we present an upper bound to the difference $λ_{1,Ω}^ω- λ_{1,B}^ω$ where the last named eigenvalue corresponds to a disk of the same area as $Ω$.

math.SP↗

A magnetic version of the Smilansky-Solomyak model

We analyze spectral properties of two mutually related families of magnetic Schrödinger operators, $H_{\mathrm{Sm}}(A)=(i \nabla +A)^2+ω^2 y^2+λy δ(x)$ and $H(A)=(i \nabla +A)^2+ω^2 y^2+ λy^2 V(x y)$ in $L^2(R^2)$, with the parameters $ω>0$ and $λ<0$, where $A$ is a vector potential corresponding to a homogeneous magnetic field perpendicular to the plane and $V$ is a regular nonnegative and compactly supported potential. We show that the spectral properties of the operators depend crucially on the one-dimensional Schrödinger operators $L= -\frac{\mathrm{d}^2}{\mathrm{d}x^2} +ω^2 +λδ(x)$ and $L (V)= - \frac{\mathrm{d}^2}{\mathrm{d}x^2} +ω^2 +λV(x)$, respectively. Depending on whether the operators $L$ and $L(V)$ are positive or not, the spectrum of $H_{\mathrm{Sm}}(A)$ and $H(V)$ exhibits a sharp transition.

math.SP↗

A regular analogue of the Smilansky model: spectral properties

We analyze spectral properties of the operator $H=\frac{\partial^2}{\partial x^2} -\frac{\partial^2}{\partial y^2} +ω^2y^2-λy^2V(x y)$ in $L^2(\mathbb{R}^2)$, where $ω\ne 0$ and $V\ge 0$ is a compactly supported and sufficiently regular potential. It is known that the spectrum of $H$ depends on the one-dimensional Schrödinger operator $L=-\frac{\mathrm{d}^2}{\mathrm{d}x^2}+ω^2-λV(x)$ and it changes substantially as $\infσ(L)$ switches sign. We prove that in the critical case, $\infσ(L)=0$, the spectrum of $H$ is purely essential and covers the interval $[0,\infty)$. In the subcritical case, $\infσ(L)>0$, the essential spectrum starts from $ω$ and there is a non-void discrete spectrum in the interval $[0,ω)$. We also derive a bound on the corresponding eigenvalue moments.

math-ph↗