7,572 research outputs found
Spontaneous Dissociation of 85Rb Feshbach Molecules
The spontaneous dissociation of 85Rb dimers in the highest lying vibrational
level has been observed in the vicinity of the Feshbach resonance which was
used to produce them. The molecular lifetime shows a strong dependence on
magnetic field, varying by three orders of magnitude between 155.5 G and 162.2
G. Our measurements are in good agreement with theoretical predictions in which
molecular dissociation is driven by inelastic spin relaxation. Molecule
lifetimes of tens of milliseconds can be achieved close to resonance.Comment: 4 pages, 3 figure
Microlocal spectrum condition and Hadamard form for vector-valued quantum fields in curved spacetime
Some years ago, Radzikowski has found a characterization of Hadamard states
for scalar quantum fields on a four-dimensional globally hyperbolic spacetime
in terms of a specific form of the wavefront set of their two-point functions
(termed `wavefront set spectrum condition'), thereby initiating a major
progress in the understanding of Hadamard states and the further development of
quantum field theory in curved spacetime. In the present work, we extend this
important result on the equivalence of the wavefront set spectrum condition
with the Hadamard condition from scalar fields to vector fields (sections in a
vector bundle) which are subject to a wave-equation and are quantized so as to
fulfill the covariant canonical commutation relations, or which obey a Dirac
equation and are quantized according to the covariant anti-commutation
relations, in any globally hyperbolic spacetime having dimension three or
higher. In proving this result, a gap which is present in the published proof
for the scalar field case will be removed. Moreover we determine the
short-distance scaling limits of Hadamard states for vector-bundle valued
fields, finding them to coincide with the corresponding flat-space, massless
vacuum states.Comment: latex2e, 41 page
Residual entanglement of accelerated fermions is not nonlocal
We analyze the operational meaning of the residual entanglement in
non-inertial fermionic systems in terms of the achievable violation of the
Clauser-Horne-Shimony-Holt (CHSH) inequality. We demonstrate that the quantum
correlations of fermions, which were previously found to survive in the
infinite acceleration limit, cannot be considered to be non-local. The
entanglement shared by an inertial and an accelerated observer cannot be
utilized for the violation of the CHSH inequality in case of high
accelerations. Our results are shown to extend beyond the single mode
approximation commonly used in the literature.Comment: 5 pages, 3 figures; v2: minor changes, reference and section headers
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Isosymmetric manifolds in form spaces and the normal deformations of polygonal forms
AbstractForm variations are described in an appropriately constructed form space F (typically an Rn), where every point of F represents a different form. Regarding the symmetries of the forms, F can be divided into disjunct isosymmetric manifolds, i.e., points, lines, surfaces, and volumes whose points correspond to forms with equal symmetries. These manifolds are derived from a symmetry analysis of possible deformations of the forms. This analysis is comparable to the construction of symmetry coordinates in a normal coordinate analysis of molecules and results in normal modes of deformation (“normal deformations”) of these forms. From the symmetry species of a normal deformation, the symmetry of the resulting form can be inferred. Transformation of the form space coordinates into normal coordinates (the differentials of which are the normal deformations) facilitates the description of the high-dimensional form spaces and can be made the basis of an easy symmetry diagnosis of forms. Furthermore, the problem of an ascent in symmetry by deformation is discussed
Hardness of Exact Distance Queries in Sparse Graphs Through Hub Labeling
A distance labeling scheme is an assignment of bit-labels to the vertices of
an undirected, unweighted graph such that the distance between any pair of
vertices can be decoded solely from their labels. An important class of
distance labeling schemes is that of hub labelings, where a node
stores its distance to the so-called hubs , chosen so that for
any there is belonging to some shortest
path. Notice that for most existing graph classes, the best distance labelling
constructions existing use at some point a hub labeling scheme at least as a
key building block. Our interest lies in hub labelings of sparse graphs, i.e.,
those with , for which we show a lowerbound of
for the average size of the hubsets.
Additionally, we show a hub-labeling construction for sparse graphs of average
size for some , where is the
so-called Ruzsa-Szemer{\'e}di function, linked to structure of induced
matchings in dense graphs. This implies that further improving the lower bound
on hub labeling size to would require a
breakthrough in the study of lower bounds on , which have resisted
substantial improvement in the last 70 years. For general distance labeling of
sparse graphs, we show a lowerbound of , where is the communication complexity of the
Sum-Index problem over . Our results suggest that the best achievable
hub-label size and distance-label size in sparse graphs may be
for some
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