749 research outputs found
From Marginal Deformations to Confinement
We consider type IIB supergravity backgrounds which describe marginal
deformations of the Coulomb branch of N=4 super Yang-Mills theory with SO(4) x
SO(2) global symmetry. Wilson loop calculations indicate that certain
deformations enhance the Coulombic attraction between quarks and anti-quarks at
the UV conformal fixed-point. In the IR region, these deformations can induce a
transition to linear confinement.Comment: 14 pages, 4 figures, minor corrections, comments and references adde
Microscopic Description of Black Rings in AdS/CFT
We discuss some aspects of the recently discovered BPS black ring solutions
in terms of the AdS/CFT correspondence. In the type IIB frame in which the
black ring carries the charges of the D1-D5-P system, we propose a microscopic
description of the rings in the orbifold CFT governing this system. In our
proposal, the CFT effectively splits into two parts: one part captures the
supertube-like properties of the ring, and the other captures the entropy. We
can also understand the black ring entropy by relating the geometry near the
ring to BPS black holes in four dimensions, although this latter approach does
not directly lead to an identification of black rings in terms of the D1-D5-P
CFT.Comment: 18 pages, harvmac. v2 - minor typo
Entropy Functions with 5D Chern-Simons terms
In this note we reconsider Sen's entropy function analysis for 5D
supergravity actions containing Chern-Simons terms. The apparent lack of gauge
invariance is usually tackled via a 4D reduction. Here we motivate how a
systematic 5D procedure also works. In doing so, it becomes important to
identify the correct 5D charges. In particular, we perform explicit
calculations for the black ring and 5D black hole. In the black ring analysis,
we find Chern-Simons induced spectral flow shifts emerging out of Sen's
formalism. We find that the entropy function nevertheless remains gauge
invariant and the resulting electric charges are identified as Page charges.
For the black hole too, 5D gauge invariance is confirmed. Our 5D analysis
enables us to fix a mismatch that arose in the electric charges of Goldstein
and Jena's 4D-reduced calculation. Finally we provide an interpretation for the
e^0 - p^0 exchange in the entropy function as an interpolation between black
hole and black ring geometries in Taub-NUT.Comment: 27 page
Innovative behaviour, trust and perceived workplace performance
Building on theories of social exchange, enactment, and trust, we provide a theorization of innovative work behaviour at the individual (IB) and team (IBT) levels and explain how desirable performance returns occur for individuals and teams. We further propose that horizontal (between team members) and vertical (between teams and their supervisor) team trust moderate the relationship between IBT and team performance. The results based on surveys conducted at two points in time in a large insurance company in the Netherlands show that employees’ IB is positively associated with perceived workplace performance at the individual and team levels and that the effects vary based on the forms of trust at play. Our findings offer important new knowledge about the consequences of entrepreneurship and innovation in the workplace and the significant role that trust plays in enabling such behaviour to promote perceived workplace performance, particularly in the vital financial services sector
de Sitter thermodynamics and the braneworld
The de Sitter thermodynamics of cosmological models with a modified Friedmann
equation is considered, with particular reference to high-energy
Randall-Sundrum and Gauss-Bonnet braneworlds. The Friedmann equation can be
regarded as the first law of thermodynamics of an effective gravitational
theory in quasi de Sitter spacetime. The associated entropy provides some
selection rules for the range of the parameters of the models, and is proposed
for describing tunneling processes in the class of high-energy gravities under
consideration.Comment: 16 pages JHEP style, no figures. v2: references added; v3: typo
corrected in Eq.(3.1), supersedes published versio
Near the horizon of 5D black rings
For the five dimensional N=2 black rings, we study the supersymmetry
enhancement and identify the global supergroup of the near horizon geometry. We
show that the global part of the supergroup is OSp(4*|2)X U(1) which is similar
to the small black string. We show that results obtained by applying the
entropy function formalism, the c-extremization approach and the Brown-Henneaux
method to the black ring solution are in agreement with the microscopic entropy
calculation.Comment: 26 pages, version to appear in JHEP, the near horizon superalgebra is
corrected, discussion on small black ring is discarded, Brown-Henneaux
approach to large black ring is adde
General 2 charge geometries
Two charge BPS horizon free supergravity geometries are important in
proposals for understanding black hole microstates. In this paper we construct
a new class of geometries in the NS1-P system, corresponding to solitonic
strings carrying fermionic as well as bosonic condensates. Such geometries are
required to account for the full microscopic entropy of the NS1-P system. We
then briefly discuss the properties of the corresponding geometries in the dual
D1-D5 system.Comment: 44 page
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Femtosecond time-resolved MeV electron diffraction
We report the experimental demonstration of femtosecond electron diffraction using high-brightness MeV electron beams. High-quality, single-shot electron diffraction patterns for both polycrystalline aluminum and single-crystal 1T-TaS2 are obtained utilizing a 5 fC (~3 Ă— 104 electrons) pulse of electrons at 2.8 MeV. The high quality of the electron diffraction patterns confirms that electron beam has a normalized emittance of ~50 nm rad. The transverse and longitudinal coherence length is ~11 and ~2.5 nm, respectively. The timing jitter between the pump laser and probe electron beam was found to be ~100 fs (rms). The temporal resolution is demonstrated by observing the evolution of Bragg and superlattice peaks of 1T-TaS2 following an 800 nm optical pump and was found to be 130 fs. Our results demonstrate the advantages of MeV electrons, including large elastic differential scattering cross-section and access to high-order reflections, and the feasibility of ultimately realizing below 10 fs time-resolved electron diffraction
Fast Non-Adiabatic Two Qubit Gates for the Kane Quantum Computer
In this paper we apply the canonical decomposition of two qubit unitaries to
find pulse schemes to control the proposed Kane quantum computer. We explicitly
find pulse sequences for the CNOT, swap, square root of swap and controlled Z
rotations. We analyze the speed and fidelity of these gates, both of which
compare favorably to existing schemes. The pulse sequences presented in this
paper are theoretically faster, higher fidelity, and simpler than existing
schemes. Any two qubit gate may be easily found and implemented using similar
pulse sequences. Numerical simulation is used to verify the accuracy of each
pulse scheme
Spin effects in the magneto-drag between double quantum wells
We report on the selectivity to spin in a drag measurement. This selectivity
to spin causes deep minima in the magneto-drag at odd fillingfactors for
matched electron densities at magnetic fields and temperatures at which the
bare spin energy is only one tenth of the temperature. For mismatched densities
the selectivity causes a novel 1/B-periodic oscillation, such that negative
minima in the drag are observed whenever the majority spins at the Fermi
energies of the two-dimensional electron gasses (2DEGs) are anti-parallel, and
positive maxima whenever the majority spins at the Fermi energies are parallel.Comment: 4 pages, 3 figure
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