59,079 research outputs found
Analytic ranks of elliptic curves over number fields
Let be an elliptic curves over the rational numbers. Let be a cyclic
extension of prime degree . Then, we show that the average of analytic ranks
of over all cyclic extension of prime degree is at most
, where is the analytic rank of . This bound is independent of the degree of the cyclic extension. Also, we
also obtain some average rank result over -fields
Velocity statistics from spectral line data: effects of density-velocity correlations, magnetic field, and shear
In a previous work Lazarian and Pogosyan suggested a technique to extract
velocity and density statistics, of interstellar turbulence, by means of
analysing statistics of spectral line data cubes. In this paper we test that
technique, by studying the effect of correlation between velocity and density
fields, providing a systematic analysis of the uncertainties arising from the
numerics, and exploring the effect of a linear shear. We make use of both
compressible MHD simulations and synthetic data to emulate spectroscopic
observations and test the technique. With the same synthetic spectroscopic
data, we also studied anisotropies of the two point statistics and related
those anisotropies with the magnetic field direction. This presents a new
technique for magnetic field studies. The results show that the velocity and
density spectral indices measured are consistent with the analytical
predictions. We identified the dominant source of error with the limited number
of data points along a given line of sight. We decrease this type of noise by
increasing the number of points and by introducing Gaussian smoothing. We argue
that in real observations the number of emitting elements is essentially
infinite and that source of noise vanishes.Comment: 12 pages, 10 figures. Accepted for publication in MNRA
Schwinger Effect in Non-parallel D1-branes: A Path Integral Approach
We study the Schwinger effect in a system of non-parallel D1-branes for the
bosonic strings using the path integral formalism. We drive the string pair
creation rate by calculating the one loop vacuum amplitude of the setup in
presence of the background electric filed defined along one of the D1-branes.
We find an angle dependent minimum value for the background field and show that
the decaying of vacuum into string pairs takes place for the field above this
value. It is shown that in limit the vacuum
becomes stable and thus no pair creation occurs
Kinetically-controlled thin-film growth of layered - and NaCoO cobaltate
We report growth characteristics of epitaxial -NaCoO and
-NaCoO thin films on (001) sapphire substrates grown by
pulsed-laser deposition. Reduction of deposition rate could change structure of
NaCoO thin film from -phase with island growth mode to
-phase with layer-by-layer growth mode. The
-NaCoO thin film exhibits spiral surface growth with
multiterraced islands and highly crystallized texture compared to that of the
-NaCoO thin film. This heterogeneous epitaxial film growth
can give opportunity of strain effect of physical properties and growth
dynamics of NaCoO as well as subtle nature of structural change.Comment: accepted for publication in Applied Physics Letter
Requirement for Slit-1 and Robo-2 in zonal segregation of olfactory sensory neuron axons in the main olfactory bulb
The formation of precise stereotypic connections in sensory systems is critical for the ability to detect and process signals from the environment. In the olfactory system, olfactory sensory neurons (OSNs) project axons to spatially defined glomeruli within the olfactory bulb (OB). A spatial relationship exists between the location of OSNs within the olfactory epithelium (OE) and their glomerular targets
along the dorsoventral axis in the OB. The molecular mechanisms underlying the zonal segregation of OSN axons along the dorsoventral axis of the OB are poorly understood. Using robo-2/ (roundabout) and slit-1/ mice, we examined the role of the Slit family of axon
guidance cues in the targeting of OSN axons during development. We show that a subset of OSN axons that normally project to the dorsal region of the OB mistarget and form glomeruli in the ventral region in robo-2/ and slit-1/ mice. In addition, we show that the Slit
receptor, Robo-2, is expressed in OSNs in a high dorsomedial to low ventrolateral gradient across the OE and that Slit-1 and Slit-3 are expressed in the ventral region of the OB. These results indicate that the dorsal-to-ventral segregation of OSN axons are not solely defined
by the location of OSNs within the OE but also relies on axon guidance cues
Supersymmetric gauged Double Field Theory: Systematic derivation by virtue of \textit{Twist}
In a completely systematic and geometric way, we derive maximal and
half-maximal supersymmetric gauged double field theories in lower than ten
dimensions. To this end, we apply a simple twisting ansatz to the
ungauged maximal and half-maximal supersymmetric double field theories
constructed previously within the so-called semi-covariant formalism. The
twisting ansatz may not satisfy the section condition. Nonetheless, all the
features of the semi-covariant formalism, including its complete
covariantizability, are still valid after the twist under alternative
consistency conditions. The twist allows gaugings as supersymmetry preserving
deformations of the untwisted theories after Scherk-Schwarz-type
dimensional reductions. The maximal supersymmetric twist requires an extra
condition to ensure both the Ramond-Ramond gauge symmetry and the
supersymmetries unbroken.Comment: 1+58 pages, section 4 enhanced, refs added. To appear in JHE
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