1,504 research outputs found
The Impact of Tennessee Promise on Community College Enrollment, Retention, and Persistence
The Impact of Tennessee Promise on Community College Enrollment, Retention, and Persistenc
Black Hole Horizon Fluctuations
It is generally admitted that gravitational interactions become large at an
invariant distance of order from the black hole horizon. We show that due
to the ``atmosphere'' of high angular particles near the horizon strong
gravitational interactions already occur at an invariant distance of the order
of . The implications of these results for the origin of black
hole radiation, the meaning of black hole entropy and the information puzzle
are discussed.Comment: Latex, 22 pages (minor corrections and precisions added
E11 and Spheric Vacuum Solutions of Eleven- and Ten dimensional Supergravity Theories
In view of the newly conjectured Kac-Moody symmetries of supergravity
theories placed in eleven and ten dimensions, the relation between these
symmetry groups and possible compactifications are examined. In particular, we
identify the relevant group cosets that parametrise the vacuum solutions of AdS
x S type.Comment: discussion improve
Abrupt and gradual changes of information through the Kane solid state computer
The susceptibility of the transformed information to the filed and system
parameters is investigated for the Kane solid state computer. It has been
shown, that the field polarization and the initial state of the system play the
central roles on the abrupt and gradual quench of the purity and the fidelity.
If the field and the initial state are in different polarizations, then the
purity and the fidelity decrease abruptly, while for the common polarization
the decay is gradual and smooth. For some class of initial states one can send
the information without any loss. Therefore, by controlling on the devices one
can increase the time of safe communication, reduce the amount of exchange
information between the state and its environment and minimize the purity
decrease rate
Long-lived qubit from three spin-1/2 atoms
A system of three spin-1/2 atoms allows the construction of a
reference-frame-free (RFF) qubit in the subspace with total angular momentum
. The RFF qubit stays coherent perfectly as long as the spins of the
three atoms are affected homogeneously. The inhomogeneous evolution of the
atoms causes decoherence, but this decoherence can be suppressed efficiently by
applying a bias magnetic field of modest strength perpendicular to the plane of
the atoms. The resulting lifetime of the RFF qubit can be many days, making RFF
qubits of this kind promising candidates for quantum information storage units.
Specifically, we examine the situation of three atoms trapped
in a -laser-generated optical lattice and find that, with
conservatively estimated parameters, a stored qubit maintains a fidelity of
0.9999 for two hours.Comment: 15 pages, 9 figures; version 2 reports a much improved analysis;
version 3 contains more details about the four-atom cas
QCD Corrections to Vector-Boson Fusion Processes in Warped Higgsless Models
We discuss the signatures of a representative Higgsless model with ideal
fermion delocalization in vector-boson fusion processes, focusing on the gold-
and silver-plated decay modes of the gauge bosons at the CERN-Large Hadron
Collider. For this purpose, we have developed a fully-flexible parton-level
Monte-Carlo program, which allows for the calculation of cross sections and
kinematic distributions within experimentally feasible selection cuts at
NLO-QCD accuracy. We find that Kaluza-Klein resonances give rise to very
distinctive distributions of the decay leptons. Similar to the Standard Model
case, within the Higgsless scenario the perturbative treatment of the
vector-boson scattering processes is under excellent control.Comment: 22 pages, 20 figure
E_{11} origin of Brane charges and U-duality multiplets
We derive general equations which determine the decomposition of the G^{+++}
multiplet of brane charges into the sub-algebras that arise when the
non-linearly realised G^{+++} theory is dimensionally reduced on a torus. We
apply this to calculate the low level E_8 multiplets of brane charges that
arise when the E_{8}^{+++}, or E_{11}, non-linearly realised theory is
dimensionally reduced to three dimensions on an eight dimensional torus. We
find precise agreement with the U-duality multiplet of brane charges previously
calculated, thus providing a natural eleven dimensional origin for the
"mysterious" brane charges found that do not occur as central charges in the
supersymmetry algebra. We also discuss the brane charges in nine dimensions and
how they arise from the IIA and IIB theories.Comment: 30 pages, plain te
Duality in linearized gravity
We show that duality transformations of linearized gravity in four
dimensions, i.e., rotations of the linearized Riemann tensor and its dual into
each other, can be extended to the dynamical fields of the theory so as to be
symmetries of the action and not just symmetries of the equations of motion.
Our approach relies on the introduction of two "superpotentials", one for the
spatial components of the spin-2 field and the other for their canonically
conjugate momenta. These superpotentials are two-index, symmetric tensors. They
can be taken to be the basic dynamical fields and appear locally in the action.
They are simply rotated into each other under duality. In terms of the
superpotentials, the canonical generator of duality rotations is found to have
a Chern-Simons like structure, as in the Maxwell case.Comment: 10 pages; introduction rewritten and references adde
Environment assisted entanglement enhancement
We consider dissipative atom-cavity systems and show that their collective
dynamics leads to the maximization of entanglement for intermediate values of
the cavity leakage parameter . We discuss possible ways the reservoir
influences entanglement. We first consider the entanglement of a single
two-level atom with a microwave cavity that is coupled to another cavity. We
show that the atom-cavity entanglement can be made to increase with cavity
leakage. We next show that the entanglement between two atoms passing
successively through a cavity can be maximised for intermediate values of
. We finally consider the micromaser where the increase of two-atom
entanglement for stronger cavity-environment coupling is demonstrated for
experimentally attainable values of the micromaser parameters.Comment: 4 pages, Revtex, 1 eps figure; minor changes to match with published
versio
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