276 research outputs found
Proof of an entropy conjecture for Bloch coherent spin states and its generalizations
Wehrl used Glauber coherent states to define a map from quantum density
matrices to classical phase space densities and conjectured that for Glauber
coherent states the mininimum classical entropy would occur for density
matrices equal to projectors onto coherent states. This was proved by Lieb in
1978 who also extended the conjecture to Bloch SU(2) spin-coherent states for
every angular momentum . This conjecture is proved here. We also recall our
1991 extension of the Wehrl map to a quantum channel from to , with corresponding to the Wehrl map to classical densities.
For each and we show that the minimal output entropy for
these channels occurs for a coherent state. We also show that coherent
states both Glauber and Bloch minimize any concave functional, not just
entropy.Comment: Version 2 only minor change
Extended quantum conditional entropy and quantum uncertainty inequalities
Quantum states can be subjected to classical measurements, whose
incompatibility, or uncertainty, can be quantified by a comparison of certain
entropies. There is a long history of such entropy inequalities between
position and momentum. Recently these inequalities have been generalized to the
tensor product of several Hilbert spaces and we show here how their derivations
can be shortened to a few lines and how they can be generalized. All the
recently derived uncertainty relations utilize the strong subadditivity (SSA)
theorem; our contribution relies on directly utilizing the proof technique of
the original derivation of SSA.Comment: 4 page
On Blowup for time-dependent generalized Hartree-Fock equations
We prove finite-time blowup for spherically symmetric and negative energy
solutions of Hartree-Fock and Hartree-Fock-Bogoliubov type equations, which
describe the evolution of attractive fermionic systems (e. g. white dwarfs).
Our main results are twofold: First, we extend the recent blowup result of
[Hainzl and Schlein, Comm. Math. Phys. \textbf{287} (2009), 705--714] to
Hartree-Fock equations with infinite rank solutions and a general class of
Newtonian type interactions. Second, we show the existence of finite-time
blowup for spherically symmetric solutions of a Hartree-Fock-Bogoliubov model,
where an angular momentum cutoff is introduced. We also explain the key
difficulties encountered in the full Hartree-Fock-Bogoliubov theory.Comment: 24 page
Postoperative Befunde an der WirbelsÀule
Zusammenfassung: Die postoperative Bildgebung wird klassischerweise herangezogen zur Dokumentation der korrekten Implantatlage oder um Komplikationen auszuschlieĂen, wenn der Patient postoperativ weiterhin Beschwerden angibt. In AbhĂ€ngigkeit von der Fragestellung können verschiedene ModalitĂ€ten verwendet werden - alle mit Vor- und Nachteilen. Die konventionelle Röntgenuntersuchung wird zur Dokumentation der Implantatlage, Beurteilung der StabilitĂ€t oder im Follow-up zur Frage der InstabilitĂ€t oder einer Implantatfraktur verwendet, wogegen WeichteilverĂ€nderungen nicht komplett beurteilt werden können. Neben diesen Indikationen wird eine Bildgebung bei persistierenden Beschwerden (meist Schmerzen) des Patienten veranlasst. Residuelles oder rezidiviertes Bandscheibengewebe, ein HĂ€matom oder eine EntzĂŒndung können am besten mit der MRT beurteilt werden. Die MRT sollte unmittelbar postoperativ durchgefĂŒhrt werden, um eine physiologische Granulation im Zugangsgebiet von entzĂŒndlichen VerĂ€nderungen unterscheiden zu können. Oft kann die Bildgebung allein dies nicht unterscheiden, daher ist die Bildgebung nur ein weiteres PuzzelstĂŒck. Die Computertomographie ist die ModalitĂ€t der Wahl zur Beurteilung von Knochen und eine ErgĂ€nzung bei neuen Verfahren wie der bildgestĂŒtzten Kypho- oder Vertebroplasti
Charged stripes from alternating static magnetic field
We motivate and perform a calculation of the energy of a cold fluid of
charged fermions in the presence of a striped magnetic background. We find that
a non-trivial value for the doping density on the walls is preferredComment: RevTeX, 3 pages, 3 encapsulated PostScript figure
EntzĂŒndliche Erkrankungen der WirbelsĂ€ule und des Myelons
Zusammenfassung: EntzĂŒndliche Erkrankungen der WirbelsĂ€ule und des Myelons haben vielfĂ€ltige Ursachen. Mit Ausnahme der degenerativ bedingten entzĂŒndlichen VerĂ€nderungen der WirbelsĂ€ule selbst sind bakteriell, viral oder autoimmun vermittelte EntzĂŒndungen eher selten. Letztere sind klinisch und bildgebend auch schwer zu evaluieren, können aber wichtige Ursachen fĂŒr Schmerzen und funktionelle Störungen sein. Dies gilt besonders, wenn sie unbehandelt bleiben. Bei schweren KrankheitsverlĂ€ufen wie der Spondylodiszitis oder der rheumatoiden Arthritis kann es zu ernsten neurologischen AusfĂ€llen kommen, v.a. bei fortschreitender intraspinaler Beteiligung. EntzĂŒndungen des Myelons selbst können durch konventionelle Röntgenuntersuchungen nicht und mit der Computertomographie nur selten festgestellt werden. Hier ist die Magnetresonanztomographie das bildgebende Verfahren der ersten Wahl, um VerĂ€nderungen des Myelons frĂŒhzeitig und differenziert zu beurteile
Spin-spin correlation functions of the XXZ-1/2 Heisenberg chain in a magnetic field
Using algebraic Bethe ansatz and the solution of the quantum inverse
scattering problem, we compute compact representations of the spin-spin
correlation functions of the XXZ-1/2 Heisenberg chain in a magnetic field. At
lattice distance m, they are typically given as the sum of m terms. Each term n
of this sum, n = 1,...,m is represented in the thermodynamic limit as a
multiple integral of order 2n+1; the integrand depends on the distance as the
power m of some simple function. The root of these results is the derivation of
a compact formula for the multiple action on a general quantum state of the
chain of transfer matrix operators for arbitrary values of their spectral
parameters.Comment: 34 page
Charge and Spin Quantum Fluids Generated by Many-Electron Interactions
In this paper we describe the electrons of the 1D Hubbard model by a fluid of
unpaired rotated electrons and a fluid of zero-spin rotated-electron pairs. The
rotated electrons are related to the original electrons by a mere unitary
transformation. For all finite values of energy and for the whole parameter
space of the model this two-fluid picture leads to a description of the energy
eigenstates in terms of occupancy configurations of -spin 1/2 holons,
spin 1/2 spinons, and pseudoparticles only. The electronic degrees of
freedom couple to external charge (and spin) probes through the holons and
pseudoparticles (and spinons). Our results refer to very large values of the
number of lattice sites . The holon (and spinon) charge (and spin
transport is made by -holon (and -spinon) composite pseudoparticles
such that .Comment: 25 pages, no figure
Mean field effects in a trapped classical gas
In this article, we investigate mean field effects for a bosonic gas
harmonically trapped above the transition temperature in the collisionless
regime. We point out that those effects can play also a role in low dimensional
system. Our treatment relies on the Boltzmann equation with the inclusion of
the mean field term.
The equilibrium state is first discussed. The dispersion relation for
collective oscillations (monopole, quadrupole, dipole modes) is then derived.
In particular, our treatment gives the frequency of the monopole mode in an
isotropic and harmonic trap in the presence of mean field in all dimensions.Comment: 4 pages, no figure submitted to Phys. Rev.
Correlation functions of the XXZ spin-1/2 Heisenberg chain at the free fermion point from their multiple integral representations
Using multiple integral representations, we derive exact expressions for the
correlation functions of the spin-1/2 Heisenberg chain at the free fermion
point.Comment: 24 pages, LaTe
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