528 research outputs found
Coherent Destruction of Photon Emission from a Single Molecule Source
The behavior of a single molecule driven simultaneously by a laser and by an
electric radio frequency field is investigated using a non-Hermitian
Hamiltonian approach. Employing the renormalization group method for
differential equations we calculate the average waiting time for the first
photon emission event to occur, and determine the conditions for the
suppression and enhancement of photon emission. An abrupt transition from
localization-like behavior to delocalization behavior is found.Comment: 5 pages, 4 figure
Π ΠΏΠΎΡΡΡΠΎΠ΅Π½ΠΈΠΈ ΡΠΈΡΠΊΡΠ»ΡΠ½ΡΠ½ΡΡ ΠΌΠ°ΡΡΠΈΡ, ΡΠ²ΡΠ·Π°Π½Π½ΡΡ Ρ MDS-ΠΌΠ°ΡΡΠΈΡΠ°ΠΌΠΈ
The objective of this paper is to suggest a method of the construction of circulant ma-trices, which are appropriate for being MDS (Maximum Distance Separable) matrices utilising in cryptography. Thus, we focus on designing so-called bi-regular circulant matrices, and furthermore, impose additional restraints on matrices in order that they have the maximal number of some element occurrences and the minimal number of distinct elements. The reason to construct bi-regular matrices is that any MDS matrix is necessarily the bi-regular one, and two additional restraints on matrix elements grant that matrix-vector multiplication for the samples constructed may be performed effciently. The results obtained include an upper bound on the number of some ele-ment occurrences for which the circulant matrix is bi-regular. Furthermore, necessary and sucient conditions for the circulant matrix bi-regularity are derived. On the ba-sis of these conditions, we developed an effcient bi-regularity verication procedure. Additionally, several bi-regular circulant matrix layouts of order up to 31 with the maximal number of some element occurrences are listed. In particular, it appeared that there are no layouts of order 32 with more than 5 occurrences of any element which yield a bi-regular matrix (and hence an MDS matrix)
Majorana fermions in pinned vortices
Exploiting the peculiar properties of proximity-induced superconductivity on
the surface of a topological insulator, we propose a device which allows the
creation of a Majorana fermion inside the core of a pinned Abrikosov vortex.
The relevant Bogolyubov-de Gennes equations are studied analytically. We
demonstrate that in this system the zero-energy Majorana fermion state is
separated by a large energy gap, of the order of the zero-temperature
superconducting gap , from a band of single-particle non-topological
excitations. In other words, the Majorana fermion remains robust against
thermal fluctuations, as long as the temperature remains substantially lower
than the critical superconducting temperature. Experimentally, the Majorana
state may be detected by measuring the tunneling differential conductance at
the center of the Abrikosov vortex. In such an experiment, the Majorana state
manifests itself as a zero-bias anomaly separated by a gap, of the order of
, from the contributions of the nontopological excitations.Comment: 9 pages, 2 eps figures, new references are added, several typos are
correcte
Instabilities of the AA-stacked graphene bilayer
Tight-binding calculations predict that the AA-stacked graphene bilayer has
one electron and one hole conducting bands, and that the Fermi surfaces of
these bands coincide. We demonstrate that as a result of this degeneracy, the
bilayer becomes unstable with respect to a set of spontaneous symmetry
violations. Which of the symmetries is broken depends on the microscopic
details of the system. We find that antiferromagnetism is the more stable order
parameter. This order is stabilized by the strong on-site Coulomb repulsion.
For an on-site repulsion energy typical for graphene systems, the
antiferromagnetic gap can exist up to room temperatures.Comment: 4 pages, 2 eps figure, submitted to Phys. Rev. Let
Density-density propagator for one-dimensional interacting spinless fermions with non-linear dispersion and calculation of the Coulomb drag resistivity
Using bosonization-fermionization transformation we map the
Tomonaga-Luttinger model of spinless fermions with non-linear dispersion on the
model of fermionic quasiparticles whose interaction is irrelevant in the
renormalization group sense. Such mapping allows us to set up an expansion for
the density-density propagator of the original Tomonaga-Luttinger Hamiltonian
in orders of the (irrelevant) quasiparticle interaction. The lowest order term
in such an expansion is proportional to the propagator for free fermions. The
next term is also evaluated. The propagator found is used for calculation of
the Coulomb drug resistivity in a system of two capacitively coupled
one-dimensional conductors. It is shown that is proportional to for
both free and interacting fermions. The marginal repulsive in-chain interaction
acts to reduce as compared to the non-interacting result. The correction to
due to the quasiparticle interaction is found as well. It scales as
at low temperature.Comment: 5 pages, 1 eps figure; the new version of the e-print corrects an
error, which exists in the original submission; fortunately, all important
conclusions of the study remain vali
Aggregated estimation of the basic parameters of biological production and the carbon budget of Russian terrestrial ecosytems: 2. Net primary production
The estimated net primary production (NPP) of Russian terrestrial ecosystems (annual average over the period from 1988 to 1992) is 9544 Tg of dry matter, or 4353 Tg of carbon. Of the total amount, forests account for approximately 39.2% (here and below, comparisons are made with respect to carbon content); natural grasslands and brushwoods, for 27.6%; farmlands (arable land and cultivated pastures), for 22.0%; and wetlands, for 11.2%. The average NPP density on lands covered with vegetation (1629.8 million hectares in Russia) is 267 g C/m2per year. The highest value (498 g C/m2per year) is characteristic of arable lands. Other land-use/land-cover (LULC) classes have the following NPP densities (in areas covered with vegetation): grasslands and brushwoods, 278 g C/m2; forests, 224 g C/m2; and wetlands, 219 g C/m2per year. In general, Russian terrestrial ecosystems accumulate 59.7% of the total NPP in the aboveground phytomass (47.8% in green parts and 11.9% in wood) and 40.3% in the underground phytomass. The latter parameter differs significantly in different LULC classes and bioclimatic zones. According to calculations, the uncertainty in estimating the total NPP is 11% (a priori confidential probability 0.9)
Suspensions of supracolloidal magnetic polymers: self-assembly properties from computer simulations
We study self-assembly in suspensions of supracolloidal polymer-like
structures made of crosslinked magnetic particles. Inspired by self-assembly
motifs observed for dipolar hard spheres, we focus on four different topologies
of the polymer-like structures: linear chains, rings, Y-shaped and X-shaped
polymers. We show how the presence of the crosslinkers, the number of beads in
the polymer and the magnetic interparticle interaction affect the structure of
the suspension. It turns out that for the same set of parameters, the rings are
the least active in assembling larger structures, whereas the system of Y- and
especially X-like magnetic polymers tend to form very large loose aggregates
A nearly closed ballistic billiard with random boundary transmission
A variety of mesoscopic systems can be represented as a billiard with a
random coupling to the exterior at the boundary. Examples include quantum dots
with multiple leads, quantum corrals with different kinds of atoms forming the
boundary, and optical cavities with random surface refractive index. The
specific example we study is a circular (integrable) billiard with no internal
impurities weakly coupled to the exterior by a large number of leads with one
channel open in each lead. We construct a supersymmetric nonlinear
-model by averaging over the random coupling strengths between bound
states and channels. The resulting theory can be used to evaluate the
statistical properties of any physically measurable quantity in a billiard. As
an illustration, we present results for the local density of states.Comment: 5 pages, 1 figur
Stem-technologies: mathematics and informatics
Algorithms solutions of tasks in the field of the theory of numbers within implementation of the STEM project are proposed and realized. Calculations in a package of computer algebra on an open code in the environment of Linux DebianΠΡΠ΅Π΄Π»ΠΎΠΆΠ΅Π½Ρ ΠΈ ΡΠ΅Π°Π»ΠΈΠ·ΠΎΠ²Π°Π½Ρ Π°Π»Π³ΠΎΡΠΈΡΠΌΡ ΡΠ΅ΡΠ΅Π½ΠΈΡ Π·Π°Π΄Π°Ρ Π² ΠΎΠ±Π»Π°ΡΡΠΈ ΡΠ΅ΠΎΡΠΈΠΈ ΡΠΈΡΠ΅Π» Π² ΡΠ°ΠΌΠΊΠ°Ρ
ΡΠ΅Π°Π»ΠΈΠ·Π°ΡΠΈΠΈ ΠΏΡΠΎΠ΅ΠΊΡΠ° STEM. ΠΡΡΠΈΡΠ»Π΅Π½ΠΈΡ Π² ΠΏΠ°ΠΊΠ΅ΡΠ΅ ΠΊΠΎΠΌΠΏΡΡΡΠ΅ΡΠ½ΠΎΠΉ Π°Π»Π³Π΅Π±ΡΡ Π½Π° ΠΎΡΠΊΡΡΡΠΎΠΌ ΠΊΠΎΠ΄Π΅ Π² ΡΡΠ΅Π΄Π΅ Linux Debia
Experimental (computing) theory of numbers
Carrying out numerical experiments with Euler's function. Specification of the theorem of Mertens. Calculations in a package of computer algebra on an open code in the environment of Linux DebianΠΡΠΎΠ²Π΅Π΄Π΅Π½ΠΈΠ΅ ΡΠΈΡΠ»Π΅Π½Π½ΡΡ
ΡΠΊΡΠΏΠ΅ΡΠΈΠΌΠ΅Π½ΡΠΎΠ² Ρ ΡΡΠ½ΠΊΡΠΈΠ΅ΠΉ ΠΠΉΠ»Π΅ΡΠ°. Π£ΡΠΎΡΠ½Π΅Π½ΠΈΠ΅ ΡΠ΅ΠΎΡΠ΅ΠΌΡ ΠΠ΅ΡΡΠ΅Π½ΡΠ°. ΠΡΡΠΈΡΠ»Π΅Π½ΠΈΡ Π² ΠΏΠ°ΠΊΠ΅ΡΠ΅ ΠΊΠΎΠΌΠΏΡΡΡΠ΅ΡΠ½ΠΎΠΉ Π°Π»Π³Π΅Π±ΡΡ Π½Π° ΠΎΡΠΊΡΡΡΠΎΠΌ ΠΊΠΎΠ΄Π΅ Π² ΡΡΠ΅Π΄Π΅ Linux Debia
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