Questions tagged [schrodinger-operators]
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1
vote
1answer
345 views
A question of the Schrodinger Semigroup --By B. Simon
The question comes from the paper: B. Simon, Schrodinger Semigroups, Bull. A.M.S., (1982) Vol. 7 (3).
On the Theorem C.1.2(subsolution estimate) of the paper, it says that: If $Hu=0$, where $H=-\...
3
votes
1answer
105 views
Lower estimate of the minimal eigenvalue of a Hamiltonian
Consider a linear operator $H\colon L^2(\mathbb{R}^3)\to L^2(\mathbb{R}^3)$ given by
$$H(\psi)(x):=-\Delta\psi(x)+V(x)\cdot \psi(x),$$
where $V\colon \mathbb{R}^3\to \mathbb{R}$ is a continuous (or ...
0
votes
0answers
123 views
Sudden appearance of an eigenvalue of a self-adjoint operator $H = H_0 + \lambda H_1$
In doing some numerical calculation in quantum mechanics, we found something surprising to us. Let the Hamiltonian be
$$ H = H_0 + \lambda H_1 , $$
where both $H_0$ and $H_1$ are self-adjoint, and $...
5
votes
1answer
120 views
Anderson localization for fractional Laplacians
There is a vast literature on Anderson localization, namely, the study of decay of eigenfunctions of operators on $l^2(\mathbb{Z}^d)$ such as
$$
-\Delta+\lambda V
$$
where $\Delta$ is the discrete ...
0
votes
0answers
40 views
What are tools we need to prove scattering result for NLS when propagator is unitary?
Consider nonlinear Schrödinger equation (NLS)
$$i\partial_t u + \Delta u =F(u) , u(x,0)=u_0$$
where $F$ is some nonlinearity.
Assume that there exists Banach space $X$ so that $\|e^{it\Delta} f\|_{X}...
1
vote
0answers
68 views
relative compact on nonlinear term
On the paper: Decay of Solutions to Nonlinear Schrodinger
Equations.
Let $u$ be a solution of the equation
$$Hu+|u|^2u=0,$$
where $H$ is a Schrodinger operator, i.e. $-\Delta+V$ and $V$ is a (...
4
votes
0answers
70 views
Anderson Localization and Homogenization theory
I originally asked this on Mathematics Stack Exchange but realized it might be better to ask it here.
The question is mostly related to homogenization theory in mathematical physics.
$\textbf{...
2
votes
2answers
137 views
Criteria for Schrödinger operator on real line to have simple spectrum
Consider a Schrödinger operator $H:=-\Delta+V$ on $\mathbb R$, where $V$ is such that $H$ has a purely discrete spectrum
$-\infty<\lambda_1\leq\lambda_2\leq\cdots$ converging to $+\infty$. Do there ...
0
votes
1answer
214 views
Elementary quantum scattering problem on the line.
Let us consider the quantum scattering problem on the line with the Hamiltonian
$$H=-\frac{d^2}{dx^2}+ V(x),$$
where $V(x)=1$ when $x\in (0,a)$, and $V(x)=0$ otherwise.
It is easy to see that $H$ ...
1
vote
2answers
173 views
Fourier transform of a generalized function on the plane
Is there an explicit formula for the Fourier transform of the generalized function of 2 variables
$$\frac{1}{x+y^2+i0}?$$
Remark. Equivalent question: consider the Schroedinger equation one the ...
4
votes
0answers
70 views
Difference Between Eigenvalues of Schrödinger Operator with Different Boundary Conditions
Consider a Schrödinger operator
$$H=-\Delta+V$$
on a nice bounded domain $\Omega\subset\mathbb R^d$ (say, a ball or a cube), and assume for simplicity that $V$ is smooth.
Let $\lambda_D,\lambda_N$ ...
0
votes
3answers
135 views
Single quantum particle entropy
Consider a wave function of a single particle in free space, whose evolution is described by the (non-dimensional) linear Schrodinger equation $$i\psi _t (t,\underline{x}) + \Delta \psi=V(\underline{x}...
0
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0answers
70 views
Spectrum of a Hamiltonian on the real line
Consider the following linear (Hamiltonian) operator on functions on the real line $\mathbb{R}$
$$H\psi(x)=-\frac{d^2}{dx^2}\psi(x)+V(x)\psi(x).$$
Assume that $V$ is a smooth function and $V(x)\to +\...
2
votes
1answer
142 views
Barry Simon's decay of eigenfunctions for pseudo differential operators
In his celebrated paper on Schrödinger semigroups, Barry Simon proves the following result.
Let $V_{-} \in K_\nu$, $V_{+} \in K_\nu^{\mathrm{loc}}$ and suppose that $Hu=Eu$ where $E$ is the ...
0
votes
0answers
73 views
Discrete spectrum of Schrodinger operator
Assume $\Omega$ is a non-compact region or manifold with dimension $\geq4$. Let $H=-\Delta+V$ be Schrodinger operator. Here $V$ is a (smooth)function.
I know that if $V\geq c>0$ or $V\to c>0$,...
1
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0answers
45 views
Realizing $N$-body Hamiltonian operator from $2$-body operator
Let $N\in\mathbb{N}$, and consider the formal $N$-body Schrodinger operator
$$\sum_{j=1}^{N}-\partial_{x_{j}}^{2}+2c\sum_{1\leq j_{1}<j_{2}\leq N}\delta(X_{j_{1}}-X_{j_{2}}), \tag{1}$$
where $c\in\...
1
vote
0answers
111 views
Perturbation of Elliptic operator
Let $\Omega$ be an open region or a non-compact complete manifold, $L$ be an elliptic operator with possibly non vanishing zero-order term, e.g. $-\Delta+q$. Suppose $W$ is an operator such that $W(...
1
vote
0answers
55 views
Zero energy resonances for scaling critical Schrodinger operators
Given a real valued potential $V\in L^1(\mathbb{R}^3)$, we say that the Schrodinger operator $-\Delta + V$ has a zero-energy resonance if there exists $\psi\in L^2_{loc}(\mathbb{R}^3)\setminus L^2(\...
1
vote
1answer
99 views
Lower bound of the spectrum of a Schrodinger operator on a bounded domain
I am trying to look for references on estimate of the lower bound of the spectrum of a Schrodinger operator $-\Delta + V$ on a bounded domain in three-dimensional space. For simplicity, we can take ...
2
votes
1answer
216 views
Spectrum of magnetic Laplacian
Consider the discrete magnetic Laplacian on $\mathbb Z^2.$
$$(\Delta_{\alpha,\lambda}\psi)(n_1,n_2) = e^{-i \pi \alpha n_2} \psi(n_1+1,n_2) + e^{i\pi \alpha n_2} \psi(n_1-1,n_2) + \lambda \left(e^{i ...
0
votes
2answers
136 views
Limit (at infinity) for the lowest eigenvalue of a perturbed harmonic oscillator
Let $\epsilon \in [0, \infty[$. Consider the following operator on $L^2(\mathbb{R})$:
\begin{equation}
H(\epsilon) = -\frac{d^2}{dx^2} + x^2 + \epsilon |x|.
\end{equation}
How does one show that the ...
2
votes
1answer
151 views
the asymptotic behaviour of function as $\lambda \to -\infty$
Let's consider the following differential equation on $\mathbb{R}$:
$$-u''(x)+u(x)-V(x)u(x)=\lambda u(x),$$ where $\lambda<1$ and $V$ is a bounded.
We consider only that solution $u(x) \in C^1$ ...
0
votes
2answers
146 views
Ground state has always constant sign?
Question: What hypothesis on the potential $V$ are required such that the ground state $\phi_0$ has constant sign?
Consider the Schrödinger operator in 1 dimension with potential $V$:
$$\mathcal{H}=-...
2
votes
1answer
90 views
Pseudo-polynomial potentials for Schrödinger operators
Consider the one dimensional Schrödinger hamiltonian $\mathcal{H}=-\frac{\hbar^2}{2} \frac{d^2}{dx^2} + V(x)$.
Suppose that $V:\mathbb{R} \rightarrow \mathbb{R}^+$ is a continuous and confining ...
0
votes
1answer
103 views
Why does it hold: the “observation” from Error Bounds for Exponential Operator Splittings by Jahnke & Lubich
In the paper, Tobias Jahnke and Christian Lubich (2000), "Error bounds for exponential operator splittings." BIT Numerical Mathematics,
(Here is the link for the paper: http://www.math.kit.edu/ianm3/~...
1
vote
0answers
65 views
Time dependent Hamiltonians
I'm studying time dependent perturbation theory on Reed-Simon book "Method of modern mathematical physics, II". If one considers an Hamiltonian of the form
$$H(t)=H_0+V(t)$$
the corresponding formal ...
2
votes
1answer
176 views
Ground state for a double well potential (Schrödinger)
Consider $V(x)$ a one dimensional polynomial, confining, symmetric double well potential i.e.
$V(x)=V(-x)$ for all $x\in\mathbb{R}$
$\displaystyle \lim_{x\to\pm\infty} V(x)=+\infty$
$V(x)\in \mathbb{...
1
vote
0answers
58 views
When Schroedinger propagator commutes other operators?
Let $f\in \mathcal{S}(\mathbb R^d)$ (Schwartz Space).
We know that $\widehat{\nabla f}(\xi)= 2 \pi i \xi \hat{f} (\xi). $ We define $$\widehat{|\nabla| f^{s}} (\xi) = (2 \pi |\xi|)^s \hat{f} (\xi), ...
6
votes
2answers
308 views
Schrödinger eigenfunctions are bounded
Let $V:\mathbb{R}\rightarrow \mathbb{R}^{+ *}$ a real positive function such that $\displaystyle \lim_{ x \to \pm\infty} V(x)= +\infty $.
Then the Schrödinger operator $H=-\frac{d^2}{dx^2}+V(x)$ has ...
2
votes
0answers
179 views
Existence of solutions to time-dependent Schrödinger equations
I would like to know what is known about evolution equations of the form
$$iy'(t)=H_0y(x,t)+u(t)V(x)y(x,t)$$
and $y(0)=y_0 \in D(H_0)$
where
$V$ is not a bounded operator, but an unbounded one, $u \...
3
votes
2answers
206 views
Minimum eigenvalue of One-dimensional Schrodinger Operator
Consider the One dimensional Schrodinger Operator
$$
-\frac{d^2}{dx^2} + V(x)
$$
Where the Potential Function $V$ is of the form $V(x) = x^4 - a^2x^2$ , $a \in \mathbb{R} $.
Now of course,the ...
4
votes
1answer
198 views
Spectral growth of One dimensional Schrodinger Operator
Conside the One dimentional Schrodinger Operator
$$
-\frac{d^2}{dx^2} + ( V(x) + E )
$$
Where the Potential Function $V$ is of the form $V(x) = ax^2 + b^2x^4$ , $a,b \in \mathbb{R} $.
What is known ...
0
votes
1answer
261 views
Invariance of sets under Schrödinger equations
We are considering the Schrödinger equation on $\mathbb{R}^d \times [0,T]$
$$i \partial_t \psi(x,t)=-\Delta \psi(x,t) + u(t)V(x) \psi(x,t), t>0$$
$$\psi(x,0):=\psi(x_0) \in L^2(\mathbb{R}^d)$$
...
2
votes
0answers
94 views
Quantitative Approach to Existence of Minimal-Mass Blowup Solutions to NLS
Consider the mass-critical defocusing NLS in dimension $d\geq 1$:
$$iu_{t}+\Delta u = |u|^{4/d}u, \quad (t,x) \in I\times\mathbb{R}^{2}$$
Define the mass $M(u)$ and scattering size $S(u)$ of the ...
1
vote
0answers
55 views
Eignfunctions of an elliptic operator
I am looking for a reference which makes it possible to say that one can devellop $f$ in the form of the sentence underlined by the yellow.
Thank you in advance.
2
votes
1answer
158 views
Resolvents of Schrodinger operators
In the free case one can compute the resolvents of the Laplacian $-\Delta$ in many cases explicitly, in the sense that they are given by an integral operator. Often, one uses the Hille-Yosida theorem ...
0
votes
1answer
113 views
Solutions to Schrödinger equation parameter dependence
This is somewhat unrelated to what I normally do in mathematics, which is why it may be obvious to some of you, but I was puzzled by this:
If we look for classical solutions on $[0,1]$ to
$$-y''(x) =...
0
votes
2answers
127 views
Concerning the decay of the ground state of certain Schrodinger operators
Consider the Schrodinger operator in $n$ dimensions with a potential $V$, which grows rather quickly as $\mid x\mid$ tends to infinity, but with negative potential in a bounded region, for example, a ...
1
vote
1answer
54 views
Dispersive estimates for one dimensional magnetic Schrodinger operators
I would like to know if there is any known result on dispersive estimates for Schrodinger operator with magnetic potential in one dimension.
There is a lot of literature for three dimensional magnetic ...
3
votes
1answer
370 views
Birman-Schwinger Principle
The Birman-Schwinger principle says that if $\Delta$ is the usual Laplacian on $\mathbb{R}^n$ and we consider the operator $H=-\Delta-V$ for a positive potential $V$, then, for any $\lambda>0$, the ...
1
vote
0answers
41 views
Delta function propogation in the NLS regime
consider the $(1+1)D$ or $(2+1)D$ NLS:
$$ i\psi _t (t,{\bf x}) + \Delta \psi + |\psi|^2\psi = 0 \, ,$$
$$ \psi (t,|{\bf x}|\to \infty) =0 \, , \quad \psi(t=0,{\bf x}) = \psi_0 ({\bf x}) \, , $$
with $...
3
votes
1answer
129 views
Operator norm of almost mathieu operator
The almost Mathieu operator has become famous since it is the central object of the ten martini problem.
In this paper here a bound on the operator norm is given. Although the bound is of course ...
4
votes
1answer
437 views
Question about normalization factors in the direct integral of operators
So the original question I wanted to ask was this one:
I'm currently a bit puzzled about the normalization for the Gelfand transform $U$:
So if we have a periodic Schrödinger operator $H$, then we ...
0
votes
0answers
65 views
Spectrum analytic in quasimomenta?
This is rather a reference request than a research question.
As far as I know the following statement is true:
Let $ H(k)\psi = -\psi''+V \psi$ where $V \in L^2[0,1]$ and the domain of $H(k)$ is
$$...
0
votes
0answers
50 views
Sub-matrices with a real spectrum
This question arises from the study of PT-symmetric quantum mechanics.
Let $A$ be an $n\times n$ complex-valued matrix with a real spectrum.
If $A$ is Hermitian, then any sub-matrix corresponding to ...
5
votes
2answers
191 views
Gap-opening perturbations of the periodic Schrödinger operator
I am trying to understand this short paper and I am getting stuck right at the end.
Let $V(x)$ be $C^\infty$ and 1-periodic (that is, $V(x)=V(x+1)$).
We are considering the operator
$$A=-\dfrac{d^2}...
1
vote
0answers
379 views
estimate of smallest eigenvalue of Schrodinger operator
I am looking for references on estimate of first nonzero Dirichlet eigenvalue for Schrodinger operator $-\Delta + V$, if sharp bounds exist, that would be better, here for simplicity, we can assume ...
3
votes
1answer
158 views
Bounded solutions for Schrödinger equation at the edge of the essential spectrum
Let $V:R^d\to R_+$ be with a compact support. The Schrödinger operator $H_a=-\Delta - a V$ acting in $L^2(R^d)$ has then (at most) finitely many negative eigenvalues. Denote the number of negative ...
10
votes
3answers
879 views
Connection between solution for Schrödinger equation and solution for heat equation
It's known, that if you write imaginary unit into a heat equation you'll get time-dependent Schrödinger equation. Recently one guy discovered a connection between solutions for these two equations (...
2
votes
0answers
68 views
When does the ground state energy continuously depend on a parameter?
Given a family of Schrödinger operators $H_\gamma=-\Delta+V_\gamma$, under which condition is the map $\gamma\mapsto\inf\sigma(H_\gamma)$ continuous?
This is surely the case for many textbook ...
