351 research outputs found
A solution of a problem of Sophus Lie: Normal forms of 2-dim metrics admitting two projective vector fields
We give a complete list of normal forms for the 2-dimensional metrics that
admit a transitive Lie pseudogroup of geodesic-preserving transformations and
we show that these normal forms are mutually non-isometric. This solves a
problem posed by Sophus Lie.Comment: This is an extended version of the paper that will appear in Math.
Annalen. Some typos were corrected, references were updated, title was
changed (as in the journal version). 31 page
Gallot-Tanno Theorem for closed incomplete pseudo-Riemannian manifolds and applications
We extend the Gallot-Tanno Theorem to closed pseudo-Riemannian manifolds. It
is done by showing that if the cone over a manifold admits a parallel symmetric
tensor then it is Riemannian. Applications of this result to the
existence of metrics with distinct Levi-Civita connections but having the same
unparametrized geodesics and to the projective Obata conjecture are given. We
also apply our result to show that the holonomy group of a closed
-manifold does not preserve any nondegenerate splitting of
.Comment: minor correction
On Dual Formulation for Higher Spin Gauge Fields in
We obtain dual actions for spin massless fields in by
solving different algebraic constraints in the same first-order theory. Flat
space dual higher spin actions obtained by Boulanger, Cnockaert and Henneaux
\cite{BH} by solving differential constraints are shown to result from our
formulation in a sort of quasi-classical approximation for the flat limit. The
case of is considered in detail.Comment: LaTeX, 13 pages, no figure
A method for obtaining Darboux transformations
In this paper we give a method to obtain Darboux transformations (DTs) of
integrable equations. As an example we give a DT of the dispersive water wave
equation. Using the Miura map, we also obtain the DT of the Jaulent-Miodek
equation. \end{abstract
Thermopower of a single electron transistor in the regime of strong inelastic cotunneling
We study Coulomb blockade oscillations of thermoelectric coefficients of a
single electron transistor based on a quantum dot strongly coupled to one of
the leads by a quantum point contact. At temperatures below the charging energy
E_C the transport of electrons is dominated by strong inelastic cotunneling. In
this regime we find analytic expressions for the thermopower as a function of
temperature T and the reflection amplitude in the contact. In the case when
the electron spins are polarized by a strong external magnetic field, the
thermopower shows sinusoidal oscillations as a function of the gate voltage
with the amplitude of the order of . We obtain
qualitatively different results in the absence of the magnetic field. At
temperatures between and the thermopower oscillations are
sinusoidal with the amplitude of order . On the
other hand, at we find non-sinusoidal oscillations of the
thermopower with the amplitude .Comment: 14 pages, 3 figure
Coulomb blockade of strongly coupled quantum dots studied via bosonization of a channel with a finite barrier
A pair of quantum dots, coupled through a point contact, can exhibit Coulomb
blockade effects that reflect an oscillatory term in the dots' total energy
whose value depends on whether the total number of electrons on the dots is
even or odd. The effective energy associated with this even-odd alternation is
reduced, relative to the bare Coulomb blockade energy for uncoupled dots, by a
factor (1-f) that decreases as the interdot coupling is increased. When the
transmission coefficient for interdot electronic motion is independent of
energy and the same for all channels within the point contact (which are
assumed uncoupled), the factor (1-f) takes on a universal value determined
solely by the number of channels and the dimensionless conductance g of each
individual channel.
This paper studies corrections to the universal value of (1-f) that result
when the transmission coefficent varies over energy scales of the size of the
bare Coulomb blockade energy. We consider a model in which the point contact is
described by a single orbital channel containing a parabolic barrier potential,
and we calculate the leading correction to (1-f) for one-channel (spin-split)
and two-channel (spin-degenerate) point contacts in the limit where the single
orbital channel is almost completely open. By generalizing a previously used
bosonization technique, we find that, for a given value of the dimensionless
conductance g, the value of (1-f) is increased relative to its value for a
zero-thickness barrier, but the absolute value of the increase is small in the
region where our calculations apply.Comment: 13 pages, 3 Postscript figure
Proof of projective Lichnerowicz conjecture for pseudo-Riemannian metrics with degree of mobility greater than two
We prove an important partial case of the pseudo-Riemannian version of the
projective Lichnerowicz conjecture stating that a complete manifold admitting
an essential group of projective transformations is the round sphere (up to a
finite cover).Comment: 32 pages, one .eps figure. The version v1 has a misprint in Theorem
1: I forgot to write the assumption that the degree of mobility is greater
than two. The versions v3, v4 have only cosmetic changes wrt v
CONJUGATE HEAT TRANSFER SIMILATION OF HIGH PRESSURE TURBINE NOZZLE GUIDE VANES OPERATING UNDER REAL LOAD CONDITIONS
This research is focused on the conjugate heat transfer simulation of nozzle guide vanes. In order to properly es¬timate blade temperature distribution the real boundary conditions were considered. Both measured radial and circum¬ferential distortion after combustion chamber were used. It allowed us to predict local increase in blade temperature and temperature gradient determining the stress-stain .state. Apart from that, the hot gases radiation was taken into account that helps us to avoid overestimated values of cooling efficiency
Distributed networked control system for power supply system of the accelerator based on CANopen protocol
Network-based control system for a power supply unit of the linear accelerator was developed. Front-end level
of the system is based on CAN fieldbus with CANopen and CANEX application level protocols. Both local and remote
control for each CANopen node is provided. Level 2 control stations of the system are ARM9 CPU based machines,
operating under Linux OS.Разработана распределенная сетевая система управления для силового источника питания линейного ускорителя. Нижний уровень системы основан на технологии полевой шины CAN с прикладными протоколами CANopen и CANEX. Поддерживается локальный и удаленный доступ к каждому CANopen узлу. В компьютерах станций управления второго уровня используется процессор ARM9 с операционной системой Linux OS.Розроблено розподілену мережну систему керування для силового джерела живлення лінійного
прискорювача. Нижній рівень системи заснований на технології польової шини CAN із прикладними
протоколами CANopen і CANEX. Підтримується локальний і вилучений доступ до кожного CANopen вузлу.
У комп’ю-терах станцій керування другого рівня використається процесор ARM9 з операційною системою
Linux OS
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