24,160 research outputs found
Necesary and sufficient range-dimension conditions for bipartite quantum correlations
Necessary and sufficient conditions for the existence of a composite-system
statistical operator, and, separately, for the possibility of its being
correlated or uncorrelated, are derived in terms of its range dimension and the
range dimensions of its reduced statistical operators.Comment: 6 pages, Latex 2
Perturbation Theory of Schr\"odinger Operators in Infinitely Many Coupling Parameters
In this paper we study the behavior of Hamilton operators and their spectra
which depend on infinitely many coupling parameters or, more generally,
parameters taking values in some Banach space. One of the physical models which
motivate this framework is a quantum particle moving in a more or less
disordered medium. One may however also envisage other scenarios where
operators are allowed to depend on interaction terms in a manner we are going
to discuss below. The central idea is to vary the occurring infinitely many
perturbing potentials independently. As a side aspect this then leads naturally
to the analysis of a couple of interesting questions of a more or less purely
mathematical flavor which belong to the field of infinite dimensional
holomorphy or holomorphy in Banach spaces. In this general setting we study in
particular the stability of selfadjointness of the operators under discussion
and the analyticity of eigenvalues under the condition that the perturbing
potentials belong to certain classes.Comment: 25 pages, Late
Effective Equations of Motion for Quantum Systems
In many situations, one can approximate the behavior of a quantum system,
i.e. a wave function subject to a partial differential equation, by effective
classical equations which are ordinary differential equations. A general method
and geometrical picture is developed and shown to agree with effective action
results, commonly derived through path integration, for perturbations around a
harmonic oscillator ground state. The same methods are used to describe
dynamical coherent states, which in turn provide means to compute quantum
corrections to the symplectic structure of an effective system.Comment: 31 pages; v2: a new example, new reference
Constraining supersymmetry from the satellite experiments
In this paper we study the detectability of -rays from dark matter
annihilation in the subhalos of the Milky Way by the satellite-based
experiments, EGRET and GLAST. We work in the frame of supersymmetric extension
of the standard model and assume the lightest neutralino being the dark matter
particles. Based on the N-body simulation of the evolution of dark matter
subhalos we first calculate the average intensity distribution of this new
class of -ray sources by neutralino annihilation. It is possible to
detect these -ray sources by EGRET and GLAST. Conversely, if these
sources are not detected the nature of the dark matter particls will be
constrained by these experiments, which, however, depending on the
uncertainties of the subhalo profile.Comment: 19 pages, 5 gigures; references added, more discussions adde
Dynamical phase transition for a quantum particle source
We analyze the time evolution describing a quantum source for noninteracting
particles, either bosons or fermions. The growth behaviour of the particle
number (trace of the density matrix) is investigated, leading to spectral
criteria for sublinear or linear growth in the fermionic case, but also
establishing the possibility of exponential growth for bosons. We further study
the local convergence of the density matrix in the long time limit and prove
the semiclassical limit.Comment: 24 pages; In the new version, we added several references concerning
open quantum systems and present an extended result on linear particle
production in the fermionic cas
The effects of space radiation on a chemically modified graphite-epoxy composite material
The effects of the space environment on the engineering properties and chemistry of a chemically modified T300/934 graphite-epoxy composite system are characterized. The material was subjected to 1.0 x 10 to the 10th power rads of 1.0 MeV electron irradiation under vacuum to simulate 30 years in geosynchronous earth orbit. Monotonic tension tests were performed at room temperature (75 F/24 C) and elevated temperature (250 F/121 C) on 4-ply unidirectional laminates. From these tests, inplane engineering and strength properties (E sub 1, E sub 2, Nu sub 12, G sub 12, X sub T, Y sub T) were determined. Cyclic tests were also performed to characterize energy dissipation changes due to irradiation and elevated temperature. Large diameter graphite fibers were tested to determine the effects of radiation on their stiffness and strength. No significant changes were observed. Dynamic-mechanical analysis demonstrated that the glass transition temperature was reduced by 50 F(28 C) after irradiation. Thermomechanical analysis showed the occurrence of volatile products generated upon heating of the irradiated material. The chemical modification of the epoxy did not aid in producing a material which was more radiation resistant than the standard T300/934 graphite-epoxy system. Irradiation was found to cause crosslinking and chain scission in the polymer. The latter produced low molecular weight products which plasticize the material at elevated temperatures and cause apparent material stiffening at low stresses at room temperature
Whirling Waves and the Aharonov-Bohm Effect for Relativistic Spinning Particles
The formulation of Berry for the Aharonov-Bohm effect is generalized to the
relativistic regime. Then, the problem of finding the self-adjoint extensions
of the (2+1)-dimensional Dirac Hamiltonian, in an Aharonov-Bohm background
potential, is solved in a novel way. The same treatment also solves the problem
of finding the self-adjoint extensions of the Dirac Hamiltonian in a background
Aharonov-Casher
Scaling limits of integrable quantum field theories
Short distance scaling limits of a class of integrable models on
two-dimensional Minkowski space are considered in the algebraic framework of
quantum field theory. Making use of the wedge-local quantum fields generating
these models, it is shown that massless scaling limit theories exist, and
decompose into (twisted) tensor products of chiral, translation-dilation
covariant field theories. On the subspace which is generated from the vacuum by
the observables localized in finite light ray intervals, this symmetry can be
extended to the M\"obius group. The structure of the interval-localized
algebras in the chiral models is discussed in two explicit examples.Comment: Revised version: erased typos, improved formulations, and corrections
of Lemma 4.8/Prop. 4.9. As published in RMP. 43 pages, 1 figur
Singular factorizations, self-adjoint extensions, and applications to quantum many-body physics
We study self-adjoint operators defined by factorizing second order
differential operators in first order ones. We discuss examples where such
factorizations introduce singular interactions into simple quantum mechanical
models like the harmonic oscillator or the free particle on the circle. The
generalization of these examples to the many-body case yields quantum models of
distinguishable and interacting particles in one dimensions which can be solved
explicitly and by simple means. Our considerations lead us to a simple method
to construct exactly solvable quantum many-body systems of Calogero-Sutherland
type.Comment: 17 pages, LaTe
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