388 research outputs found
Singular values of some modular functions
We study the properties of special values of the modular functions obtained
from Weierstrass P-function at imaginary quadratic points.Comment: 19 pages,corrected typo
Generation of Relativistic Electron Bunches with Arbitrary Current Distribution via Transverse-to-Longitudinal Phase Space Exchange
We propose a general method for tailoring the current distribution of
relativistic electron bunches. The technique relies on a recently proposed
method to exchange the longitudinal phase space emittance with one of the
transverse emittances. The method consists of transversely shaping the bunch
and then converting its transverse profile into a current profile via a
transverse-to-longitudinal phase-space-exchange beamline. We show that it is
possible to tailor the current profile to follow, in principle, any desired
distributions. We demonstrate, via computer simulations, the application of the
method to generate trains of microbunches with tunable spacing and
linearly-ramped current profiles. We also briefly explore potential
applications of the technique.Comment: 13 pages, 17 figure
Computing Hilbert Class Polynomials
We present and analyze two algorithms for computing the Hilbert class
polynomial . The first is a p-adic lifting algorithm for inert primes p
in the order of discriminant D < 0. The second is an improved Chinese remainder
algorithm which uses the class group action on CM-curves over finite fields.
Our run time analysis gives tighter bounds for the complexity of all known
algorithms for computing , and we show that all methods have comparable
run times
An explicit height bound for the classical modular polynomial
For a prime m, let Phi_m be the classical modular polynomial, and let
h(Phi_m) denote its logarithmic height. By specializing a theorem of Cohen, we
prove that h(Phi_m) <= 6 m log m + 16 m + 14 sqrt m log m. As a corollary, we
find that h(Phi_m) <= 6 m log m + 18 m also holds. A table of h(Phi_m) values
is provided for m <= 3607.Comment: Minor correction to the constants in Theorem 1 and Corollary 9. To
appear in the Ramanujan Journal. 17 pages
First Principles Calculation of Anomalous Hall Conductivity in Ferromagnetic bcc Fe
We perform a first principles calculation of the anomalous Hall effect in
ferromagnetic bcc Fe. Our theory identifies an intrinsic contribution to the
anomalous Hall conductivity and relates it to the k-space Berry phase of
occupied Bloch states. The theory is able to account for both dc and
magneto-optical Hall conductivities with no adjustable parameters.Comment: 4 pages, 6 figures, author list correcte
Interacting Constituents in Cosmology
Universe evolution, as described by Friedmann's equations, is determined by
source terms fixed by the choice of pressure energy-density equations
of state . The usual approach in Cosmology considers equations of
state accounting only for kinematic terms, ignoring the contribution from the
interactions between the particles constituting the source fluid. In this work
the importance of these neglected terms is emphasized. A systematic method,
based on the Statistical Mechanics of real fluids, is proposed to include them.
A toy-model is presented which shows how such interaction terms can engender
significant cosmological effects.Comment: 24 pages, 6 figures. It includes results presented in "Cosmic
Acceleration from Elementary Interactions" [arXiv:gr-qc/0512135]. Citations
added in v.
A Real-Time Capable Software-Defined Receiver Using GPU for Adaptive Anti-Jam GPS Sensors
Due to their weak received signal power, Global Positioning System (GPS) signals are vulnerable to radio frequency interference. Adaptive beam and null steering of the gain pattern of a GPS antenna array can significantly increase the resistance of GPS sensors to signal interference and jamming. Since adaptive array processing requires intensive computational power, beamsteering GPS receivers were usually implemented using hardware such as field-programmable gate arrays (FPGAs). However, a software implementation using general-purpose processors is much more desirable because of its flexibility and cost effectiveness. This paper presents a GPS software-defined radio (SDR) with adaptive beamsteering capability for anti-jam applications. The GPS SDR design is based on an optimized desktop parallel processing architecture using a quad-core Central Processing Unit (CPU) coupled with a new generation Graphics Processing Unit (GPU) having massively parallel processors. This GPS SDR demonstrates sufficient computational capability to support a four-element antenna array and future GPS L5 signal processing in real time. After providing the details of our design and optimization schemes for future GPU-based GPS SDR developments, the jamming resistance of our GPS SDR under synthetic wideband jamming is presented. Since the GPS SDR uses commercial-off-the-shelf hardware and processors, it can be easily adopted in civil GPS applications requiring anti-jam capabilities
Seroepidemiologic studies of hantavirus infection among wild rodents in California.
A total of 4,626 mammals were serologically tested for antibodies to Sin Nombre virus. All nonrodent species were antibody negative. Among wild rodents, antibody prevalence was 8.5% in murids, 1.4% in heteromyids, and < 0.1% in sciurids. Of 1,921 Peromyscus maniculatus (deer mice), 226 (11.8%) were antibody positive, including one collected in 1975. The highest antibody prevalence (71.4% of 35) was found among P. maniculatus on Santa Cruz Island, off the southern California coast. Prevalence of antibodies among deer mice trapped near sites of human cases (26.8% of 164) was significantly higher than that of mice from other sites (odds ratio = 4.5; 95% confidence interval = 1.7, 11.6). Antibody prevalence increased with rising elevation (> 1,200 meters) and correlated with a spatial cluster of hantavirus pulmonary syndrome cases in the Sierra Nevada
A Pomeron Approach to Hadron-Nucleus and Nucleus-Nucleus "Soft" Interactions at High Energy
We formulate a generalization of the Glauber formalism for hadron-nucleus and
nucleus-nucleus collisions based on the Pomeron approach to high energy
interactions. Our treatment is based on two physical assumptions (i.e. two
small parameters) : (i) that only sufficiently small distances contribute to
the Pomeron structure; and (ii) the triple Pomeron vertex (where is the Pomeron-nucleon vertex) is small. A systematic
method is developed for calculating the total, elastic and diffractive
dissociation cross sections as well as the survival probability of large
rapidity gap processes and inclusive observables, both for hadron - nucleus and
nucleus-nucleus collisions. Our approach suggests saturation of the density of
the produced hadrons in nucleus-nucleus collisions, the value of the saturation
density turns out to be large and depends on the number of nucleons in the
lightest nucleus.Comment: 54 pages, 63 figure
Capture Hi-C identifies the chromatin interactome of colorectal cancer risk loci.
Multiple regulatory elements distant from their targets on the linear genome can influence the expression of a single gene through chromatin looping. Chromosome conformation capture implemented in Hi-C allows for genome-wide agnostic characterization of chromatin contacts. However, detection of functional enhancer-promoter interactions is precluded by its effective resolution that is determined by both restriction fragmentation and sensitivity of the experiment. Here we develop a capture Hi-C (cHi-C) approach to allow an agnostic characterization of these physical interactions on a genome-wide scale. Single-nucleotide polymorphisms associated with complex diseases often reside within regulatory elements and exert effects through long-range regulation of gene expression. Applying this cHi-C approach to 14 colorectal cancer risk loci allows us to identify key long-range chromatin interactions in cis and trans involving these loci
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