26,864 research outputs found
A new code for parameter estimation in searches for gravitational waves from known pulsars
We describe the consistency testing of a new code for gravitational wave
signal parameter estimation in known pulsar searches. The code uses an
implementation of nested sampling to explore the likelihood volume. Using fake
signals and simulated noise we compare this to a previous code that calculated
the signal parameter posterior distributions on both a grid and using a crude
Markov chain Monte Carlo (MCMC) method. We define a new parameterisation of two
orientation angles of neutron stars used in the signal model (the initial phase
and polarisation angle), which breaks a degeneracy between them and allows more
efficient exploration of those parameters. Finally, we briefly describe
potential areas for further study and the uses of this code in the future.Comment: Accepted for proceedings of Amaldi 9 meetin
Quantized Casimir Force
We investigate the Casimir effect between two-dimensional electron systems
driven to the quantum Hall regime by a strong perpendicular magnetic field. In
the large separation (d) limit where retardation effects are essential we find
i) that the Casimir force is quantized in units of 3\hbar c \alpha^2/(8\pi^2
d^4), and ii) that the force is repulsive for mirrors with same type of
carrier, and attractive for mirrors with opposite types of carrier. The sign of
the Casimir force is therefore electrically tunable in ambipolar materials like
graphene. The Casimir force is suppressed when one mirror is a charge-neutral
graphene system in a filling factor \nu=0 quantum Hall state.Comment: 4.2 page
Growing Farm Size and the Distribution of Farm Payments
Crop production is shifting to much larger farms. Since government commodity payments reflect production volumes for program commodities, payments are also shifting to larger farms. In turn, the operators of very large farms have substantially higher household incomes than other farm households, and as a result government commodity payments are also shifting to much higher-income households. Since the changes in farm structure appear to be ongoing, commodity payments will likely, under current policies, continue to shift to higher income households. This brief uses 2003 Agricultural Resource Management Survey (ARMS) data to detail the shifts.Farm structure, commodity programs, farm payments, farm household income, farm income, farm program payments, ERS, USDA, Agricultural and Food Policy, Industrial Organization,
PRICE AND NONPRICE TERMS IN U.S. AGRICULTURAL CONTRACTS
The industrialization of the food system is proceeding at a rapid rate and contracting is a key element in that industrialization. The purposes of this paper are to summarize contract terms in agricultural contracts for major commodities and to assess the determinants of variations in contract prices/fees in selected commodity contracts, with an emphasis on the nonprice contract terms.Agricultural and Food Policy,
Anomalous Fisher-like zeros for the canonical partition function of noninteracting fermions
Noninteracting fermions, placed in a system with a continuous density of
states, may have zeros in the -fermion canonical partition function on the
positive real axis (or very close to it), even for a small number of
particles. This results in a singular free energy, and instability in other
thermal properties of the system. In the context of trapped fermions in a
harmonic oscillator, these zeros are shown to be unphysical. By contrast,
similar bosonic calculations with continuous density of states yield sensible
results.Noninteracting fermions, placed in a system with a continuous density
of states yield sensible results.Comment: 5 pages and 5 figure
Ion observations from geosynchronous orbit as a proxy for ion cyclotron wave growth during storm times
[1] There is still much to be understood about the processes contributing to relativistic electron enhancements and losses in the radiation belts. Wave particle interactions with both whistler and electromagnetic ion cyclotron (EMIC) waves may precipitate or accelerate these electrons. This study examines the relation between EMIC waves and resulting relativistic electron flux levels after geomagnetic storms. A proxy for enhanced EMIC waves is developed using Los Alamos National Laboratory Magnetospheric Plasma Analyzer plasma data from geosynchronous orbit in conjunction with linear theory. In a statistical study using superposed epoch analysis, it is found that for storms resulting in net relativistic electron losses, there is a greater occurrence of enhanced EMIC waves. This is consistent with the hypothesis that EMIC waves are a primary mechanism for the scattering of relativistic electrons and thus cause losses of such particles from the magnetosphere
STRUCTURAL CHANGE IN THE U.S. MEAT AND POULTRY INDUSTRIES
Market structure, concentration, meat industry, poultry industry, Industrial Organization,
Meron ground states of quantum Hall droplets
We argue that topological meron excitations, which are in a strong coupling
phase (bound in pairs) in infinite quantum Hall ferromagnets, become deconfined
in finite size quantum Hall systems. Although effectively for larger systems
meron energy grows with the size of the system, when gyromagnetic ratio is
small meron becomes the lowest lying state of a quantum Hall droplet. This
comes as a consequence of the many-body correlations built in the meron
construction that minimize the interaction energy. We demonstrate this by using
mean field ansatzes for meron wave function. The ansatzes will enable us to
consider much larger system sizes than in the previous work [A. Petkovic and
M.V. Milovanovic, PRL 98, 066808 (2007)], where fractionalization into merons
was introduced.Comment: 6 pages, 6 figure
Sommerfeld's image method in the calculation of van der Waals forces
We show how the image method can be used together with a recent method
developed by C. Eberlein and R. Zietal to obtain the dispersive van der Waals
interaction between an atom and a perfectly conducting surface of arbitrary
shape. We discuss in detail the case of an atom and a semi- infinite conducting
plane. In order to employ the above procedure to this problem it is necessary
to use the ingenious image method introduced by Sommerfeld more than one
century ago, which is a generalization of the standard procedure. Finally, we
briefly discuss other interesting situations that can also be treated by the
joint use of Sommerfeld's image technique and Eberlein-Zietal method.Comment: To appear in the proceedings of Conference on Quantum Field Theory
under the Influence of External Conditions (QFEXT11
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