6,217 research outputs found
Polarization bistability and resultant spin rings in semiconductor microcavities
The transmission of a pump laser resonant with the lower polariton branch of
a semiconductor microcavity is shown to be highly dependent on the degree of
circular polarization of the pump. Spin dependent anisotropy of
polariton-polariton interactions allows the internal polarization to be
controlled by varying the pump power. The formation of spatial patterns, spin
rings with high degree of circular polarization, arising as a result of
polarization bistability, is observed. A phenomenological model based on spin
dependent Gross-Pitaevskii equations provides a good description of the
experimental results. Inclusion of interactions with the incoherent exciton
reservoir, which provides spin-independent blueshifts of the polariton modes,
is found to be essential.Comment: 5 pages, 3 figure
Optoelectronic Methods of IR-Photometry in Solving Thermal and Physical Problems
Results of the application of optoelectronic IR-photometry methods for solving the actual thermophysical problems using high-speed photodiode temperature (pyrometric) sensors are presented. The latest achievements of the Ioffe Institute in the field of middle IR spectral range (3-6 ΞΌm) photodiode production technology are used in the sensor development. The above-mentioned middle-IR photodiode sensors are based on heterostructures from A3B5 solid solutions and they do not require forced cooling. New data on thermophysical processes taking place under the complex experimental conditions, including dynamically changing properties of the object, have been obtained. The new experimental results are based on high-speed non-contact measurements of the absolute temperature of objects directly in the exposure region of laser radiation and / or powerful electromagnetic fields. In the context of creating new experimental techniques for determining the thermophysical parameters of new promising materials the efficiency of middle- IR photodiode temperature sensors has been shown. In particular, a simple and effective measuring method for determining the heat transfer coefficient of solid objects and the pyroelectric coefficient of ferro- and pyroelectric materials is offered. The measuring method is based on laser thermowave techniques and direct noncontact measurements of the sample surface temperature under the pulsed / periodic laser action. The proposed experimental techniques make it possible to significantly improve the accuracy of measurements of thermophysical parameters of materials, and in particular, to eliminate a considerable spread of data on the parameters of the pyroelectric effect in ferroelectric materials.
Keywords: Pyrometric sensors, mid-IR photodiodes, laser thermowave techniques, heat transfer coefficient, pyroelectric coefficien
Information engine in a nonequilibrium bath
Information engines can convert thermal fluctuations of a bath at temperature
into work at rates of order per relaxation time of the
system. We show experimentally that such engines, when in contact with a bath
that is out of equilibrium, can extract much more work. We place a heavy,
micron-scale bead in a harmonic potential that ratchets up to capture favorable
fluctuations. Adding a fluctuating electric field increases work extraction up
to ten times, limited only by the strength of applied field. Our results
connect Maxwell's demon with energy harvesting and an estimate of efficiency
shows that information engines in nonequilibrium baths can greatly outperform
conventional engines.Comment: 14 pages, 9 figure
On Observational Predictions from Multidimensional Gravity
We discuss possible observational manifestations of static, spherically
symmetric solutions of a class of multidimensional theories of gravity, which
includes the low energy limits of supergravities and superstring theories as
special cases. We discuss the choice of a physical conformal frame to be used
for the description of observations. General expressions are given for (i) the
Eddington parameters and , characterizing the post-Newtonian
gravitational field of a central body, (ii) p-brane black hole temperatures in
different conformal frames and (iii) the Coulomb law modified by extra
dimensions. It is concluded, in particular, that and depend on
the integration constants and can be therefore different for different central
bodies. If, however, the Einstein frame is adopted for describing observations,
we always obtain . The modified Coulomb law is shown to be
independent of the choice of a 4-dimensional conformal frame. We also argue the
possible existence of specific multidimensional objects, T-holes, potentially
observable as bodies with mirror surfaces.Comment: 16 pages, Latex2
Gamma spectrometric method to control activity and nuclide composition of gaseous radioactive waste formed at operation of nuclear power plants
Gamma spectrometric method was developed to monitor continuously and on line radioactivity and nuclide composition of inert radioactive gases, radioactive aerosols and iodine in gas aerosol emissions from power reactor facilities. This method is based on continuous representative sampling of gas aerosol samples and quasi-continuous automated recording of nuclide composition and radioactive material emission rate. Low detectable level of the method is about 0,1 Bq/m3, highest detectable level for noble gases (Ar_41, isotopes Xe and Kr) is about 105 Bq/m
Toda p-brane black holes and polynomials related to Lie algebras
Black hole generalized p-brane solutions for a wide class of intersection
rules are obtained. The solutions are defined on a manifold that contains a
product of n - 1 Ricci-flat internal spaces. They are defined up to a set of
functions H_s obeying non-linear differential equations equivalent to Toda-type
equations with certain boundary conditions imposed. A conjecture on polynomial
structure of governing functions H_s for intersections related to semisimple
Lie algebras is suggested. This conjecture is proved for Lie algebras: A_m,
C_{m+1}, m > 0. For simple Lie algebras the powers of polynomials coincide with
the components of twice the dual Weyl vector in the basis of simple coroots.
The coefficients of polynomials depend upon the extremality parameter \mu >0.
In the extremal case \mu = 0 such polynomials were considered previously by H.
L\"u, J. Maharana, S. Mukherji and C.N. Pope. Explicit formulas for
A_2-solution are obtained. Two examples of A_2-dyon solutions, i.e. dyon in D =
11 supergravity with M2 and M5 branes intersecting at a point and Kaluza-Klein
dyon, are considered.Comment: 24 pages, Latex, typos are eliminated, a correct relation on
parameters of special block-orthogonal solution is added in third line after
eq. (4.10
Schwinger pair creation in multilayer graphene
The low energy effective field model for the multilayer graphene (at ABC
stacking) in external Electric field is considered. The Schwinger pair creation
rate and the vacuum persistence probability are calculated using the semi -
classical approach.Comment: Latex, 5 pages, accepted for publication in JETP let
Gamma spectrometric method to control activity and nuclide composition of gaseous radioactive waste formed at operation of nuclear power plants
Gamma spectrometric method was developed to monitor continuously and on line radioactivity and nuclide composition of inert radioactive gases, radioactive aerosols and iodine in gas aerosol emissions from power reactor facilities. This method is based on continuous representative sampling of gas aerosol samples and quasi-continuous automated recording of nuclide composition and radioactive material emission rate. Low detectable level of the method is about 0,1 Bq/m3, highest detectable level for noble gases (Ar_41, isotopes Xe and Kr) is about 105 Bq/m
Charged particles in crossed and longitudinal electromagnetic fields and beam guides
We consider a class of electromagnetic fields that contains crossed fields
combined with longitudinal electric and magnetic fields. We study the motion of
a classical particle (solutions of the Lorentz equations) in such fields. Then,
we present an analysis that allows one to decide which fields from the class
act as a beam guide for charged particles, and we find some time-independent
and time-dependent configurations with beam guiding properties. We demonstrate
that the Klein-Gordon and Dirac equations with all the fields from the class
can be solved exactly. We study these solutions, which were not known before,
and prove that they form complete and orthogonal sets of functions.Comment: 14 page
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