22,622 research outputs found
The MaxEnt extension of a quantum Gibbs family, convex geometry and geodesics
We discuss methods to analyze a quantum Gibbs family in the ultra-cold regime
where the norm closure of the Gibbs family fails due to discontinuities of the
maximum-entropy inference. The current discussion of maximum-entropy inference
and irreducible correlation in the area of quantum phase transitions is a major
motivation for this research. We extend a representation of the irreducible
correlation from finite temperatures to absolute zero.Comment: 8 pages, 3 figures, 34th International Workshop on Bayesian Inference
and Maximum Entropy Methods in Science and Engineering, 21-26 September 2014,
Ch\^ateau du Clos Luc\'e, Amboise, Franc
LBV (Candidate) Nebulae: Bipolarity and Outflows
The most massive evolved stars (above 50 M_sun) undergo a phase of extreme
mass loss in which their evolution is reversed from a redward to a blueward
motion in the HRD. In this phase the stars are known as Luminous Blue Variables
(LBVs) and they are located in the HRD close to the Humphreys-Davidson limit.
It is far from understood what causes the strong mass loss or what triggers the
so-called giant eruptions, active events in which in a short time a large
amount of mass is ejected. Here I will present results from a larger project
devoted to better understand LBVs through studying the LBV nebulae. These
nebulae are formed as a consequence of the strong mass loss. The analysis
concentrates on the morphology and kinematics of these nebulae. Of special
concern was the frequently observed bipolar nature of the LBV nebulae.
Bipolarity seems to be a general feature and strongly constrains models of the
LBV phase and especially of the formation of the nebulae. In addition we found
outflows from LBV nebulae, the first evidence for ongoing instabilities in the
nebulae.Comment: 2 pages, to appear in : K.A. van der Hucht, A. Herrero & C. Esteban
(eds.), A Massive Star Odyssey, from Main Sequence to Supernova, Proc. IAU
Symp. No. 212 (San Francisco: ASP
A variation principle for ground spaces
The ground spaces of a vector space of hermitian matrices, partially ordered
by inclusion, form a lattice constructible from top to bottom in terms of
intersections of maximal ground spaces. In this paper we characterize the
lattice elements and the maximal lattice elements within the set of all
subspaces using constraints on operator cones. Our results contribute to the
geometry of quantum marginals, as their lattices of exposed faces are
isomorphic to the lattices of ground spaces of local Hamiltonians.Comment: 18 pages, 2 figures, version v3 has an improved exposition, v4 has a
new non-commutative example and catches a glimpse of three qubit
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