64,034 research outputs found
Single vortex fluctuations in a superconducting chip as generating dephasing and spin flips in cold atom traps
We study trapping of a cold atom by a single vortex line in an extreme type
II superconducting chip, allowing for pinning and friction. We evaluate the
atom's spin flip rate and its dephasing due to the vortex fluctuations in
equilibrium and find that they decay rapidly when the distance to the vortex
exceeds the magnetic penetration length. We find that there are special spin
orientations, depending on the spin location relative to the vortex, at which
spin dephasing is considerably reduced while perpendicular directions have a
reduced spin flip rate. We also show that the vortex must be perpendicular to
the surface for a general shape vortex.Comment: 6 pages, 4 figure
Kink-antikink interactions in the double sine-Gordon equation and the problem of resonance frequencies
We studied the kink-antikink collision process for the "double sine-Gordon"
(DSG) equation in 1+1 dimensions at different values of the potential parameter
. For small values of we discuss the problem of resonance frequencies.
We give qualitative explanation of the frequency shift in comparison with the
frequency of the discrete level in the potential well of isolated kink. We show
that in this region of the parameter the effective long-range interaction
between kink and antikink takes place.Comment: 9 pages, LaTeX, 4 figures (eps
Androgen Receptor and Vasopressin Receptor (AVPR1a) Genetic Polymorphisms are not associated with Marital Status or Fertility among Ariaal Men of Northern Kenya
A growing body of scholarship implicates testosterone and vasopressin in male reproductive behavior, including in humans. Since hormones exert their effects through their respective receptors, an open question has been whether genetic polymorphisms in the androgen receptor and vasopressin 1a receptor (AVPR1a) impact human male social behavior. Here, we sought to test for associations between polymorphisms in the coding region of the androgen receptor and promoter region of AVPR1a in relation to marital status and fertility among pastoralist Ariaal men of northern Kenya. None of the three polymorphisms were related to marital status (single, monogamously married, polygynously married) or fertility (number of current living children). We discuss these null findings in light of existing data
Discrete local altitude sensing device Patent
Device for use in descending spacecraft as altitude sensor for actuating deceleration retrorocket
A technology development program for large space antennas
The design and application of the offset wrap rib and the maypole (hoop/column) antenna configurations are described. The NASA mission model that generically categorizes the classes of user requirements, as well as the methods used to determine critical technologies and requirements are discussed. Performance estimates for the mesh deployable antenna selected for development are presented
Integrated support structure
This Major Qualifying Project is part of the Advanced Space Design Program at WPI. The goal is to design a support structure for a NASA GetAway Special experimental canister. The payload integration, weight, volume, and structural integrity of the canister as specified by NASA guidelines were studied. The end result is a complete set of design drawings with interface drawings and data to specify the design and leave a base on which the next group can concentrate
Effect of Disorder in the Frustrated Ising FCC Antiferromagnet: Phase Diagram and Stretched Exponential Relaxation
We study the phase transition in a face-centered-cubic antiferromagnet with
Ising spins as a function of the concentration of ferromagnetic bonds
randomly introduced into the system. Such a model describes the spin-glass
phase at strong bond disorder. Using the standard Monte Carlo simulation and
the powerful Wang-Landau flat-histogram method, we carry out in this work
intensive simulations over the whole range of . We show that the first-order
transition disappears with a tiny amount of ferromagnetic bonds, namely , in agreement with theories and simulations on other 3D models. The
antiferromagnetic long-range order is also destroyed with a very small
(). With increasing , the system changes into a spin glass and
then to a ferromagnetic phase when . The phase diagram in the space
() shows an asymmetry, unlike the case of the Ising spin glass
on the simple cubic lattice. We calculate the relaxation time around the
spin-glass transition temperature and we show that the spin autocorrelation
follows a stretched exponential relaxation law where the factor is equal to
at the transition as suggested by the percolation-based theory.
This value is in agreement with experiments performed on various spin glasses
and with Monte Carlo simulations on different SG models
A rapidly expanding Bose-Einstein condensate: an expanding universe in the lab
We study the dynamics of a supersonically expanding ring-shaped Bose-Einstein
condensate both experimentally and theoretically. The expansion redshifts
long-wavelength excitations, as in an expanding universe. After expansion,
energy in the radial mode leads to the production of bulk topological
excitations -- solitons and vortices -- driving the production of a large
number of azimuthal phonons and, at late times, causing stochastic persistent
currents. These complex nonlinear dynamics, fueled by the energy stored
coherently in one mode, are reminiscent of a type of "preheating" that may have
taken place at the end of inflation.Comment: 12 pages, 7 figure
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