132,954 research outputs found
Inflation: Where Do We Stand?
In this short review, the predictions of inflation are presented and compared
to the most recent measurements of the Cosmic Microwave Background (CMB)
anisotropy. It is argued that inflation is compatible with these observations
but that these ones are not yet accurate enough to probe the details of the
scenario.Comment: 7 pages, no figure, Proceedings of the 8th Workshop on
Non-Perturbative Quantum Chromodynamics, June 7-11, 2004, Pari
Quirks in supersymmetry with gauge coupling unification
I investigate the phenomenology of supersymmetric models with extra
vector-like supermultiplets that couple to the Standard Model gauge fields and
transform as the fundamental representation of a new confining non-Abelian
gauge interaction. If perturbative gauge coupling unification is to be
maintained, the new group can be SU(2), SU(3), or SO(3). The impact on the
sparticle mass spectrum is explored, with particular attention to the gaugino
mass dominated limit in which the supersymmetric flavor problem is naturally
solved. The new confinement length scale is astronomical for SO(3), so the new
particles are essentially free. For the SU(2) and SU(3) cases, the new
vector-like fermions are quirks; pair production at colliders yields
quirk-antiquirk states bound by stable flux tubes that are microscopic but long
compared to the new confinement scale. I study the reach of the Tevatron and
LHC for the optimistic case that in a significant fraction of events the
quirk-antiquirk bound state will lose most of its energy before annihilating as
quirkonium.Comment: 28 page
The top squark-mediated annihilation scenario and direct detection of dark matter in compressed supersymmetry
Top squark-mediated annihilation of bino-like neutralinos to top-antitop
pairs can play the dominant role in obtaining a thermal relic dark matter
abundance in agreement with observations. In a previous paper, it was argued
that this can occur naturally in models of compressed supersymmetry, which
feature a running gluino mass parameter that is substantially smaller than the
wino mass parameter at the scale of apparent gauge coupling unification. Here I
study in some more detail the parameter space in which this is viable, and
compare to other scenarios for obtaining the observed dark matter density. I
then study the possibility of detecting the dark matter directly in future
experiments. The prospects are consistently very promising for a wide variety
of model parameters within this scenario.Comment: 17 pages. v2: additions to figures 4 and
Energy spectrum, dissipation and spatial structures in reduced Hall magnetohydrodynamic
We analyze the effect of the Hall term in the magnetohydrodynamic turbulence
under a strong externally supported magnetic field, seeing how this changes the
energy cascade, the characteristic scales of the flow and the dynamics of
global magnitudes, with particular interest in the dissipation.
Numerical simulations of freely evolving three-dimensional reduced
magnetohydrodynamics (RHMHD) are performed, for different values of the Hall
parameter (the ratio of the ion skin depth to the macroscopic scale of the
turbulence) controlling the impact of the Hall term. The Hall effect modifies
the transfer of energy across scales, slowing down the transfer of energy from
the large scales up to the Hall scale (ion skin depth) and carrying faster the
energy from the Hall scale to smaller scales. The final outcome is an effective
shift of the dissipation scale to larger scales but also a development of
smaller scales. Current sheets (fundamental structures for energy dissipation)
are affected in two ways by increasing the Hall effect, with a widening but at
the same time generating an internal structure within them. In the case where
the Hall term is sufficiently intense, the current sheet is fully delocalized.
The effect appears to reduce impulsive effects in the flow, making it less
intermittent.Comment: 17 pages, 10 figure
Optimized Monte Carlo Method for glasses
A new Monte Carlo algorithm is introduced for the simulation of supercooled
liquids and glass formers, and tested in two model glasses. The algorithm is
shown to thermalize well below the Mode Coupling temperature and to outperform
other optimized Monte Carlo methods. Using the algorithm, we obtain finite size
effects in the specific heat. This effect points to the existence of a large
correlation length measurable in equal time correlation functions.Comment: Proceedings of "X International workshop on Disordered Systems" held
in Molveno (Italy), March 200
Parallel-in-Time Multi-Level Integration of the Shallow-Water Equations on the Rotating Sphere
The modeling of atmospheric processes in the context of weather and climate
simulations is an important and computationally expensive challenge. The
temporal integration of the underlying PDEs requires a very large number of
time steps, even when the terms accounting for the propagation of fast
atmospheric waves are treated implicitly. Therefore, the use of
parallel-in-time integration schemes to reduce the time-to-solution is of
increasing interest, particularly in the numerical weather forecasting field.
We present a multi-level parallel-in-time integration method combining the
Parallel Full Approximation Scheme in Space and Time (PFASST) with a spatial
discretization based on Spherical Harmonics (SH). The iterative algorithm
computes multiple time steps concurrently by interweaving parallel high-order
fine corrections and serial corrections performed on a coarsened problem. To do
that, we design a methodology relying on the spectral basis of the SH to
coarsen and interpolate the problem in space. The methods are evaluated on the
shallow-water equations on the sphere using a set of tests commonly used in the
atmospheric flow community. We assess the convergence of PFASST-SH upon
refinement in time. We also investigate the impact of the coarsening strategy
on the accuracy of the scheme, and specifically on its ability to capture the
high-frequency modes accumulating in the solution. Finally, we study the
computational cost of PFASST-SH to demonstrate that our scheme resolves the
main features of the solution multiple times faster than the serial schemes
Shaping the future for primary care education and training project. Integrated health and social care: the perspectives of people using services: a mixed methods analysis
The aim of this study was to explore service users' perspectives concerning integrated health & social care, and
to identify the perceived strengths and weaknesses associated with the current workforce and services provided. The findings will be used to inform the education and training of
the health and social care workforce in the North West of Englan
Methodology for bus layout for topological quantum error correcting codes
Most quantum computing architectures can be realized as two-dimensional
lattices of qubits that interact with each other. We take transmon qubits and
transmission line resonators as promising candidates for qubits and couplers;
we use them as basic building elements of a quantum code. We then propose a
simple framework to determine the optimal experimental layout to realize
quantum codes. We show that this engineering optimization problem can be
reduced to the solution of standard binary linear programs. While solving such
programs is a NP-hard problem, we propose a way to find scalable optimal
architectures that require solving the linear program for a restricted number
of qubits and couplers. We apply our methods to two celebrated quantum codes,
namely the surface code and the Fibonacci code.Comment: 11 pages, 12 figure
The interannual variability of polar cap recessions as a measure of Martian climate and weather: Using Earth-based data to augment the time line for the Mars observer mapping mission
The recessions of the polar ice caps are the most visible and most studied indication of seasonal change on Mars. Circumstantial evidence links these recessions to the seasonal cycles of CO2, water, and dust. The possible advent of a planet encircling storm during the Mars Observer (MO) mission will provide a detailed correlation with a cap recession for that one Martian year. That cap recession will then be compared with other storm and nonstorm years. MO data will also provide a stronger link between cap recessions and the water and CO2 cycles. Cap recession variability might also be used to determine the variability of these cycles. After nearly a century of valiant attempts at measuring polar cap recessions, including Mariner 9 and Viking data, MO will provide the first comprehensive dataset. In contrast to MO, the older data are much less detailed and precise and could be forgotten, except that it will still be the only information on interannual variability. By obtaining simultaneous Earth-based observations (including those from Hubble) during the MO mission, direct comparisons can be made between the datasets
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