29,384 research outputs found
Residue currents associated with weakly holomorphic functions
We construct Coleff-Herrera products and Bochner-Martinelli type residue
currents associated with a tuple of weakly holomorphic functions, and show
that these currents satisfy basic properties from the (strongly) holomorphic
case, as the transformation law, the Poincar\'e-Lelong formula and the
equivalence of the Coleff-Herrera product and the Bochner-Martinelli type
residue current associated with when defines a complete intersection.Comment: 28 pages. Updated with some corrections from the revision process. In
particular, corrected and clarified some things in Section 5 and 6 regarding
products of weakly holomorphic functions and currents, and the definition of
the Bochner-Martinelli type current
Weighted integral formulas on manifolds
We present a method of finding weighted Koppelman formulas for -forms
on -dimensional complex manifolds which admit a vector bundle of rank
over , such that the diagonal of has a defining
section. We apply the method to \Pn and find weighted Koppelman formulas for
-forms with values in a line bundle over \Pn. As an application, we
look at the cohomology groups of -forms over \Pn with values in
various line bundles, and find explicit solutions to the \dbar-equation in
some of the trivial groups. We also look at cohomology groups of -forms
over \Pn \times \Pm with values in various line bundles. Finally, we apply
our method to developing weighted Koppelman formulas on Stein manifolds.Comment: 25 page
Event-by-event fluctuations of the charged particle ratio from non-equilibrium transport theory
The event by event fluctuations of the ratio of positively to negatively
charged hadrons are predicted within the UrQMD model. Corrections for finite
acceptance and finite net charge are derived. These corrections are relevant to
compare experimental data and transport model results to previous predictions.
The calculated fluctuations at RHIC and SPS energies are shown to be compatible
with a hadron gas. Thus, deviating by a factor of 3 from the predictions for a
thermalized quark-gluon plasma.Comment: This paper clarifies the previous predictions of Jeon and Koch
(hep-ph/0003168) and addresses issues raised in hep-ph/0006023. 2 Figures,
10pp, uses RevTe
On variable hydrostatic transmission for road vehicles, powered by supply of fluid at constant pressure
Various hydrostatic power transmission systems for automotive applications with power supply at constant pressure and unrestricted flow and with a Volvo Flygmotor variable displacement motor as the principal unit were investigated. Two most promising concepts were analyzed in detail and their main components optimized for minimum power loss at the EPA Urban Driving Cycle. The best fuel consumption is less than 10 lit. per 100 kM for a 1542 kG vehicle with a hydrostatic motor and a two speed gear box in series (braking power not recovered). Realistic system pressure affects the fuel consumption just slightly, but the package volume/weight drastically. Back pressure increases losses significantly. Special attention was paid to description of the behavior and modeling of the losses of variable displacement hydrostatic machines
Gravitational-wave astronomy: the high-frequency window
This contribution is divided in two parts. The first part provides a
text-book level introduction to gravitational radiation. The key concepts
required for a discussion of gravitational-wave physics are introduced. In
particular, the quadrupole formula is applied to the anticipated
``bread-and-butter'' source for detectors like LIGO, GEO600, EGO and TAMA300:
inspiralling compact binaries. The second part provides a brief review of high
frequency gravitational waves. In the frequency range above (say) 100Hz,
gravitational collapse, rotational instabilities and oscillations of the
remnant compact objects are potentially important sources of gravitational
waves. Significant and unique information concerning the various stages of
collapse, the evolution of protoneutron stars and the details of the
supranuclear equation of state of such objects can be drawn from careful study
of the gravitational-wave signal. As the amount of exciting physics one may be
able to study via the detections of gravitational waves from these sources is
truly inspiring, there is strong motivation for the development of future
generations of ground based detectors sensitive in the range from hundreds of
Hz to several kHz.Comment: 21 pages, 5 figures, Lectures presented at the 2nd Aegean Summer
School on the Early Universe, Syros, Greece, September 200
Optimal minimum-cost quantum measurements for imperfect detection
Knowledge of optimal quantum measurements is important for a wide range of
situations, including quantum communication and quantum metrology. Quantum
measurements are usually optimised with an ideal experimental realisation in
mind. Real devices and detectors are, however, imperfect. This has to be taken
into account when optimising quantum measurements. In this paper, we derive the
optimal minimum-cost and minimum-error measurements for a general model of
imperfect detection.Comment: 5 page
Spin-thermo-electronic oscillator based on inverse giant magnetoresistance
A spin-thermo-electronic valve with the free layer of exchange-spring type
and inverse magnetoresistance is investigated. The structure has S-shaped
current-voltage characteristics and can exhibit spontaneous oscillations when
integrated with a conventional capacitor within a resonator circuit. The
frequency of the oscillations can be controlled from essentially dc to the GHz
range by the circuit capacitance.Comment: 7 pages, 9 figure
Density functional theory for freezing transition of vortex-line liquid with periodic layer pinning
By the density functional theory for crystallization, it is shown that for
vortex lines in an underlying layered structure a smectic phase with period m=2
can be stabilized by strong layer pinning. The freezing of vortex liquid is
then two-step, a second-order liquid-smectic transition and a first-order
smectic-lattice transition. DFT also indicates that a direct, first-order
liquid-lattice transition preempts the smectic order with m>2 irrespectively of
the pinning strength. Possible H-T phase diagrams are mapped out. Implications
of the DFT results to the interlayer Josephson vortex system in high-Tc
cuprates are given.Comment: 4 pages, 5 figures, references adde
Spatiotemporally Complete Condensation in a Non-Poissonian Exclusion Process
We investigate a non-Poissonian version of the asymmetric simple exclusion
process, motivated by the observation that coarse-graining the interactions
between particles in complex systems generically leads to a stochastic process
with a non-Markovian (history-dependent) character. We characterize a large
family of one-dimensional hopping processes using a waiting-time distribution
for individual particle hops. We find that when its variance is infinite, a
real-space condensate forms that is complete in space (involves all particles)
and time (exists at almost any given instant) in the thermodynamic limit. The
mechanism for the onset and stability of the condensate are both rather subtle,
and depends on the microscopic dynamics subsequent to a failed particle hop
attempts.Comment: 5 pages, 5 figures. Version 2 to appear in PR
Thermoelectrical manipulation of nanomagnets
We investigate the interplay between the thermodynamic properties and
spin-dependent transport in a mesoscopic device based on a magnetic multilayer
(F/f/F), in which two strongly ferromagnetic layers (F) are exchange-coupled
through a weakly ferromagnetic spacer (f) with the Curie temperature in the
vicinity of room temperature. We show theoretically that the Joule heating
produced by the spin-dependent current allows a spin-thermo-electronic control
of the ferromagnetic-to-paramagnetic (f/N) transition in the spacer and,
thereby, of the relative orientation of the outer F-layers in the device
(spin-thermo-electric manipulation of nanomagnets). Supporting experimental
evidence of such thermally controlled switching from parallel to antiparallel
magnetization orientations in F/f(N)/F sandwiches is presented. Furthermore, we
show theoretically that local Joule heating due to a high concentration of
current in a magnetic point contact or a nanopillar can be used to reversibly
drive the weakly ferromagnetic spacer through its Curie point and thereby
exchange couple and decouple the two strongly ferromagnetic F-layers. For the
devices designed to have an antiparallel ground state above the Curie point of
the spacer, the associated spin-thermionic parallel-to-antiparallel switching
causes magneto-resistance oscillations whose frequency can be controlled by
proper biasing from essentially DC to GHz. We discuss in detail an experimental
realization of a device that can operate as a thermo-magneto-resistive switch
or oscillator.Comment: This paper, published in J. Appl. Phys. 107, 123706 (2010), is an
expanded version of arXiv:0710.5477 (8 pages, 12 figures, two additional
authors and experimental section added
- …