22,746 research outputs found
Degenerating Black Saturns
We investigate the possibility of constructing degenerate Black Saturns in
the family of solutions of Elvang-Figueras. We demonstrate that such solutions
suffer from naked singularities.Comment: 14 LaTeX page
On Projections in the Noncommutative 2-Torus Algebra
We investigate a set of functional equations defining a projection in the
noncommutative 2-torus algebra . The exact solutions of these
provide various generalisations of the Powers-Rieffel projection. By
identifying the corresponding classes we get an insight into
the structure of projections in
Teardown analysis for detecting shelf-life degradation
Analysis is guideline in examining component materials, analytically determining physical properties and chemical compositions, and developing control data necessary for ascertaining effects of environments and their influence on deterioration and degradation mechanisms
An algebraic formulation of causality for noncommutative geometry
We propose an algebraic formulation of the notion of causality for spectral
triples corresponding to globally hyperbolic manifolds with a well defined
noncommutative generalization. The causality is given by a specific cone of
Hermitian elements respecting an algebraic condition based on the Dirac
operator and a fundamental symmetry. We prove that in the commutative case the
usual notion of causality is recovered. We show that, when the dimension of the
manifold is even, the result can be extended in order to have an algebraic
constraint suitable for a Lorentzian distance formula.Comment: 24 pages, minor changes from v2, to appear in Classical and Quantum
Gravit
Ultrafast separation of photo-doped carriers in Mott antiferromagnets
We use inhomogeneous nonequilibrium dynamical mean-field theory to
investigate the spreading of photo-excited carriers in Mott insulating
heterostructures with strong internal fields. Antiferromagnetic correlations
are found to affect the carrier dynamics in a crucial manner: An
antiferromagnetic spin background can absorb energy from photo-excited carriers
on an ultrafast timescale, thus enabling fast transport between different
layers and the separation of electron and hole-like carriers, whereas in the
paramagnetic state, carriers become localized in strong fields. This interplay
between charge and spin degrees of freedom can be exploited to control the
functionality of devices based on Mott insulating heterostructures with polar
layers, e.g., for photovoltaic applications
Asymptotic and exact expansions of heat traces
We study heat traces associated with positive unbounded operators with
compact inverses. With the help of the inverse Mellin transform we derive
necessary conditions for the existence of a short time asymptotic expansion.
The conditions are formulated in terms of the meromorphic extension of the
associated spectral zeta-functions and proven to be verified for a large class
of operators. We also address the problem of convergence of the obtained
asymptotic expansions. General results are illustrated with a number of
explicit examples.Comment: 44 LaTeX pages, 2 figure
Field-assisted doublon manipulation in the Hubbard model. A quantum doublon ratchet
For the fermionic Hubbard model at strong coupling, we demonstrate that
directional transport of localized doublons (repulsively bound pairs of two
particles occupying the same site of the crystal lattice) can be achieved by
applying an unbiased ac field of time-asymmetric (sawtooth-like) shape. The
mechanism involves a transition to intermediate states of virtually zero double
occupation which are reached by splitting the doublon by fields of the order of
the Hubbard interaction. The process is discussed on the basis of numerically
exact calculations for small clusters, and we apply it to more complex states
to manipulate the charge order pattern of one-dimensional systems.Comment: 6 pages, 6 figure
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