530 research outputs found
Mutated Hilltop Inflation : A Natural Choice for Early Universe
We propose a model of inflation with a suitable potential for a single scalar
field which falls in the wide class of hilltop inflation. We derive the
analytical expressions for most of the physical quantities related to inflation
and show that all of them represent the true behavior as required from a model
of inflation. We further subject the results to observational verification by
formulating the theory of perturbations based on our model followed by an
estimation for the values of those observable parameters. Our model is found to
be in excellent agreement with observational data. Thus, the features related
to the model leads us to infer that this type of hilltop inflation may be a
natural choice for explaining the early universe.Comment: 22 pages, 7 figures, 2 tables. Matches published version in JCA
Current induced switching of magnetic domains to a perpendicular configuration
In a ferromagnet--normal-metal--ferromagnet trilayer, a current flowing
perpendicularly to the layers creates a torque on the magnetic moments of the
ferromagnets. When one of the contacts is superconducting, the torque not only
favors parallel or antiparallel alignment of the magnetic moments, as is the
case for two normal contacts, but can also favor a configuration where the two
moments are perpendicular. In addition, whereas the conductance for parallel
and antiparallel magnetic moments is the same, signalling the absence of giant
magnetoresistance in the usual sense, the conductance is greater in the
perpendicular configuration. Thus, a negative magnetoconductance is predicted,
in contrast with the usual giant magnetoresistance.Comment: 4 pages, 3 figures, major rewriting of the technical par
Nonequilibrium Josephson effect in mesoscopic ballistic multiterminal SNS junctions
We present a detailed study of nonequilibrium Josephson currents and
conductance in ballistic multiterminal SNS-devices. Nonequilibrium is created
by means of quasiparticle injection from a normal reservoir connected to the
normal part of the junction. By applying a voltage at the normal reservoir the
Josephson current can be suppressed or the direction of the current can be
reversed. For a junction longer than the thermal length, , the
nonequilibrium current increases linearly with applied voltage, saturating at a
value equal to the equilibrium current of a short junction. The conductance
exhibits a finite bias anomaly around . For symmetric
injection, the conductance oscillates -periodically with the phase
difference between the superconductors, with position of the minimum
( or ) dependent on applied voltage and temperature. For
asymmetric injection, both the nonequilibrium Josephson current and the
conductance becomes -periodic in phase difference. Inclusion of barriers
at the NS-interfaces gives rise to a resonant behavior of the total Josephson
current with respect to junction length with a period . Both
three and four terminal junctions are studied.Comment: 21 pages, 19 figures, submitted to Phys. Rev.
Tachyonic Inflation in a Warped String Background
We analyze observational constraints on the parameter space of tachyonic
inflation with a Gaussian potential and discuss some predictions of this
scenario. As was shown by Kofman and Linde, it is extremely problematic to
achieve the required range of parameters in conventional string
compactifications. We investigate if the situation can be improved in more
general compactifications with a warped metric and varying dilaton. The
simplest examples are the warped throat geometries that arise in the vicinity
of of a large number of space-filling D-branes. We find that the parameter
range for inflation can be accommodated in the background of D6-branes wrapping
a three-cycle in type IIA. We comment on the requirements that have to be met
in order to realize this scenario in an explicit string compactification.Comment: Latex, JHEP class, 20 pages, 4 figures. v2: references added, small
error in section 7 corrected, published versio
Dissolving D0-brane into D2-brane with background B-field
D0-branes on a D2-brane with a constant background B-field are unstable due
to the presence of a tachyonic mode and expected to dissolve into the D2-brane
to formulate a constant D0-charge density. In this paper we study such a
dissolution process in terms of a noncommutative gauge theory. Our results show
that the localized D0-brane spreads out over all of space on the D2-brane as
the tachyon rolls down into a stable vacuum. D0-branes on a D2-brane can be
described as unstable solitons in a noncommutative gauge theory in 2+1
dimensions in the Seiberg-Witten limit. In contrast to the case of annihilation
of a non-BPS D-brane, we are free from difficulty of disappearance of DOF,
since there exist open strings after the tachyon condensation. We solve an
equation of motion of the gauge field numerically, and our results show that
the localized soliton smears over all of noncommutative space. In addition, we
evaluate distributions of D-brane charge, F-string charge, and energy density
via formulas derived in Matrix theory. Our results show that the initial
singularities of D0-charge and energy density are resolved by turning on the
tachyon, and they disperse over the whole space on the D2-brane during the
tachyon condensation process.Comment: 42 pages, 20 figures, JHEP style; references added, clarifications
added in section 3.1; references adde
Steering of a Bosonic Mode with a Double Quantum Dot
We investigate the transport and coherence properties of a double quantum dot
coupled to a single damped boson mode. Our numerically results reveal how the
properties of the boson distribution can be steered by altering parameters of
the electronic system such as the energy difference between the dots.
Quadrature amplitude variances and the Wigner function are employed to
illustrate how the state of the boson mode can be controlled by a stationary
electron current through the dots.Comment: 10 pages, 6 figures, to appear in Phys. Rev.
The institutional shaping of management: in the tracks of English individualism
Globalisation raises important questions about the shaping of economic action by cultural factors. This article explores the formation of what is seen by some as a prime influence on the formation of British management: individualism. Drawing on a range of historical sources, it argues for a comparative approach. In this case, the primary comparison drawn is between England and Scotland. The contention is that there is a systemic approach to authority in Scotland that can be contrasted to a personal approach in England. An examination of the careers of a number of Scottish pioneers of management suggests the roots of this systemic approach in practices of church governance. Ultimately this systemic approach was to take a secondary role to the personal approach engendered by institutions like the universities of Oxford and Cambridge, but it found more success in the different institutional context of the USA. The complexities of dealing with historical evidence are stressed, as is the value of taking a comparative approach. In this case this indicates a need to take religious practice as seriously as religious belief as a source of transferable practice. The article suggests that management should not be seen as a simple response to economic imperatives, but as shaped by the social and cultural context from which it emerges
Proximity-induced screening and its magnetic breakdown in mesoscopic hybrid structures
We derive a general microscopic expression for the non-linear diamagnetic
current in a clean superconductor-insulator-normal metal structure with an
arbitrary interface transmission. In the absence of electron-electron
interactions in the normal metal the diamagnetic response increases
monotonously with decreasing temperature showing no sign of paramagnetic
reentrance down to T=0. We also analyze the magnetic breakdown of proximity
induced Meissner screening. We demonstrate that the magnetic breakdown field
should be strongly suppressed in the limit of small interface transmissions
while the linear diamagnetic current does not depend on the transmission of the
insulating barrier at low enough temperatures.Comment: 7 pages, 2 figure
Measurement of the branching fraction
The branching fraction is measured in a data sample
corresponding to 0.41 of integrated luminosity collected with the LHCb
detector at the LHC. This channel is sensitive to the penguin contributions
affecting the sin2 measurement from The
time-integrated branching fraction is measured to be . This is the most precise measurement to
date
Measurement of the CP-violating phase \phi s in Bs->J/\psi\pi+\pi- decays
Measurement of the mixing-induced CP-violating phase phi_s in Bs decays is of
prime importance in probing new physics. Here 7421 +/- 105 signal events from
the dominantly CP-odd final state J/\psi pi+ pi- are selected in 1/fb of pp
collision data collected at sqrt{s} = 7 TeV with the LHCb detector. A
time-dependent fit to the data yields a value of
phi_s=-0.019^{+0.173+0.004}_{-0.174-0.003} rad, consistent with the Standard
Model expectation. No evidence of direct CP violation is found.Comment: 15 pages, 10 figures; minor revisions on May 23, 201
- âŠ