29,396 research outputs found
Electron-Transport Properties of Na Nanowires under Applied Bias Voltages
We present first-principles calculations on electron transport through Na
nanowires at finite bias voltages. The nanowire exhibits a nonlinear
current-voltage characteristic and negative differential conductance. The
latter is explained by the drastic suppression of the transmission peaks which
is attributed to the electron transportability of the negatively biased plinth
attached to the end of the nanowire. In addition, the finding that a voltage
drop preferentially occurs on the negatively biased side of the nanowire is
discussed in relation to the electronic structure and conduction.Comment: 4 pages, 6 figure
Higher Spin Gravity with Matter in AdS_3 and Its CFT Dual
We study Vasiliev's system of higher spin gauge fields coupled to massive
scalars in AdS_3, and compute the tree level two and three point functions.
These are compared to the large N limit of the W_N minimal model, and
nontrivial agreements are found. We propose a modified version of the
conjecture of Gaberdiel and Gopakumar, under which the bulk theory is
perturbatively dual to a subsector of the CFT that closes on the sphere.Comment: 58 pages; typos corrected, references adde
On the Quantum Invariant for the Brieskorn Homology Spheres
We study an exact asymptotic behavior of the Witten-Reshetikhin-Turaev
invariant for the Brieskorn homology spheres by use of
properties of the modular form following a method proposed by Lawrence and
Zagier. Key observation is that the invariant coincides with a limiting value
of the Eichler integral of the modular form with weight 3/2. We show that the
Casson invariant is related to the number of the Eichler integrals which do not
vanish in a limit . Correspondingly there is a
one-to-one correspondence between the non-vanishing Eichler integrals and the
irreducible representation of the fundamental group, and the Chern-Simons
invariant is given from the Eichler integral in this limit. It is also shown
that the Ohtsuki invariant follows from a nearly modular property of the
Eichler integral, and we give an explicit form in terms of the L-function.Comment: 26 pages, 2 figure
Arithmetical Congruence Preservation: from Finite to Infinite
Various problems on integers lead to the class of congruence preserving
functions on rings, i.e. functions verifying divides for all
. We characterized these classes of functions in terms of sums of rational
polynomials (taking only integral values) and the function giving the least
common multiple of . The tool used to obtain these
characterizations is "lifting": if is a surjective morphism,
and a function on a lifting of is a function on such that
. In this paper we relate the finite and infinite notions
by proving that the finite case can be lifted to the infinite one. For -adic
and profinite integers we get similar characterizations via lifting. We also
prove that lattices of recognizable subsets of are stable under inverse
image by congruence preserving functions
Geometric Bogomolov conjecture for abelian varieties and some results for those with some degeneration (with an appendix by Walter Gubler: The minimal dimension of a canonical measure)
In this paper, we formulate the geometric Bogomolov conjecture for abelian
varieties, and give some partial answers to it. In fact, we insist in a main
theorem that under some degeneracy condition, a closed subvariety of an abelian
variety does not have a dense subset of small points if it is a non-special
subvariety. The key of the proof is the study of the minimal dimension of the
components of a canonical measure on the tropicalization of the closed
subvariety. Then we can apply the tropical version of equidistribution theory
due to Gubler. This article includes an appendix by Walter Gubler. He shows
that the minimal dimension of the components of a canonical measure is equal to
the dimension of the abelian part of the subvariety. We can apply this result
to make a further contribution to the geometric Bogomolov conjecture.Comment: 30 page
Structure of a translocation signal domain mediating conjugative transfer by Type IV secretion systems
Relaxases are proteins responsible for the transfer of plasmid and chromosomal DNA from one bacterium to another during conjugation. They covalently react with a specific phosphodiester bond within DNA origin of transfer sequences, forming a nucleo-protein complex which is subsequently recruited for transport by a plasmid-encoded type IV secretion system. In previous work we identified the targeting translocation signals presented by the conjugative relaxase TraI of plasmid R1. Here we report the structure of TraI translocation signal TSA. In contrast to known translocation signals we show that TSA is an independent folding unit and thus forms a bona fide structural domain. This domain can be further divided into three sub-domains with striking structural homology with helicase sub-domains of the SF1B family. We also show that TSA is part of a larger vestigial helicase domain which has lost its helicase activity but not its single-stranded DNA binding capability. Finally, we further delineate the binding site responsible for translocation activity of TSA by targeting single residues for mutations. Overall, this study provides the first evidence that translocation signals can be part of larger structural scaffolds, overlapping with translocation-independent activities
Tidal deformability of neutron stars with realistic equations of state and their gravitational wave signatures in binary inspiral
The early part of the gravitational wave signal of binary neutron star
inspirals can potentially yield robust information on the nuclear equation of
state. The influence of a star's internal structure on the waveform is
characterized by a single parameter: the tidal deformability lambda, which
measures the star's quadrupole deformation in response to the companion's
perturbing tidal field. We calculate lambda for a wide range of equations of
state and find that the value of lambda spans an order of magnitude for the
range of equation of state models considered.
An analysis of the feasibility of discriminating between neutron star
equations of state with gravitational wave observations of the early part of
the inspiral reveals that the measurement error in lambda increases steeply
with the total mass of the binary. Comparing the errors with the expected range
of lambda, we find that Advanced LIGO observations of binaries at a distance of
100 Mpc will probe only unusually stiff equations of state, while the proposed
Einstein Telescope is likely to see a clean tidal signature.Comment: 12 pages, submitted to PR
Effects of non-magnetic impurities on spin-fluctuations induced superconductivity
We study the effects of non-magnetic impurities on the phase diagram of a
system of interacting electrons with a flat Fermi surface. The one-loop
Wilsonian renormalization group flow of the angle dependent diffusion function
and interaction
determines the critical temperature and the nature of the low temperature
state. As the imperfect nesting increases the critical temperature decreases
and the low temperature phase changes from the spin-density wave (SDW) to the
d-wave superconductivity (dSC) and finally, for bad nesting, to the random
antiferromagnetic state (RAF). Both SDW and dSC phases are affected by
disorder. The pair breaking depends on the imperfect nesting and is the most
efficient when the critical temperature for superconductivity is maximal.Comment: 4 pages, 4 figures. Submitted to PR
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