119 research outputs found
BFKL pomeron in the external field of the nucleus in (2+1)-dimensional QCD
The behaviour of the pomeron propagator in the external nuclear field is
studied in the (2+1)-dimensional QCD. It is shown that in the physically
interesting case when the field does not vanish at large rapidities the
propagator in the field vanishes much faster than in the vacuum, in agreement
with the results found in the local Regge-Gribov model. However if the nuclear
field vanishes at high rapidities the field does not change the behaviour of
the pomeron propagator.Comment: 14 pages, 10 figure
Hadron-nucleus scattering in the local reggeon model with pomeron loops for realistic nuclei
Contribution of simplest loops for hadron-nucleus scattering cross-sections
is studied in the Local Reggeon Field Theory with a supercritical pomeron. It
is shown that inside the nucleus the supercritical pomeron transforms into a
subcritical one, so that perturbative treatment becomes possible. The pomeron
intercept becomes complex, which leads to oscillations in the cross-sections.Comment: 13 pages, 6 figure
Penning traps for confinement and cooling of charged particles
The parameters of confinement of trapped charged particles are compared for self-consistent electromagnetic traps and for traditional and electromagnetic traps. The possibilities to control the trapped particles dynamics are found, which allows more effective particle confinement. The main attention is paid to methods of controlling the dynamics of charge particles in the trap. Resistive cooling of particles is considered as the main cooling mechanism.Производится сравнение параметров удержания заряженных частиц в конфигурациях самосогласованной электромагнитной ловушки и традиционных электромагнитных ловушек. Показаны возможности управления динамикой удерживаемых частиц, что позволяет более эффективно удерживать и охлаждать их. Основное внимание уделено методам контроля динамики заряженных частиц в ловушке. В качестве основного рассматривается резистивный механизм охлаждения частиц.Робиться порівняння параметрів утримання заряджених частинок у конфігураціях самоузгодженої електромагнітної пастки і традиційних електромагнітних пасток. Показані можливості управління динамікою утримуваних частинок, що дозволяє ефективніше утримувати і охолоджувати їх. Основна увага приділена методам контролю динаміки заряджених частинок у пастці. В якості основного розглядається резистивний механізм охолодження частинок
Features of Magnetocaloric Effect in Er(Co-Fe)2 Laves Phases
In this work the results of measurements of heat capacity (CP) and magnetocaloric effect (MCE) in Er(Co1-хFeх)2 system in the concentration range 0.07 ≤ x ≤ 0.80 are presented. Phase composition was controlled by X-ray difraction analysis. Heat capacity was measured in the temperature range 77-320 K. MCE has been studied within the temperature range 5-670 K in magnetic fields up to 70 kOe. It was found that Fe concentration increase caused the table-like (plateau) MCE temperature dependence for both magnetic entropy change date and direct ∆T-effect measurements independently on Fe concentration. The possible reasons of such behavior are discussed
BFKL pomeron propagator in the external field of the nucleus
It is shown by numerical calculations that the convoluted QCD pomeron
propagator in the external field created by a solution of the
Balitsky-Kovchegov equation in the nuclear matter vanishes at high rapidities.
This may open a possibility to apply the perturbative approach for the
calculation of pomeron loops.Comment: 17 pages, 15 figure
Quantum and Classical Integrable Systems
The key concept discussed in these lectures is the relation between the
Hamiltonians of a quantum integrable system and the Casimir elements in the
underlying hidden symmetry algebra. (In typical applications the latter is
either the universal enveloping algebra of an affine Lie algebra, or its
q-deformation.) A similar relation also holds in the classical case. We discuss
different guises of this very important relation and its implication for the
description of the spectrum and the eigenfunctions of the quantum system.
Parallels between the classical and the quantum cases are thoroughly discussed.Comment: 59 pages, LaTeX2.09 with AMS symbols. Lectures at the CIMPA Winter
School on Nonlinear Systems, Pondicherry, January 199
Development of the method for estimating the inertia radius relative to the vertical axis of the car
The method of estimating the inertia radius relative to the vertical axis of the car is proposed. This allows
a third to reduce the relative error of its definition. A refined formula for calculating the radius of inertia design
with respect to the vertical axis of the car is proposed. The use of the proposed formula reduces the error of determining the radius of inertia from 21–27 % to 5 %, and the error of determining the inertia moment for the car from 46–61 % to 10 %. A method for assessing the adequacy of the results of theoretical and experimental studies is proposed. The use of the method has shown that the refined formula for calculating the radius of inertia relative to the vertical axis of the car makes it possible to reduce the probability of mismatching the results up to three times
Sediment history mirrors Pleistocene aridification in the Gobi Desert (Ejina Basin, NW China)
Central Asia is a large-scale source of dust transport, but it also held a prominent changing hydrological system during the Quaternary. A 223 m long sediment core (GN200) was recovered from the Ejina Basin (synonymously Gaxun Nur Basin) in NW China to reconstruct the main modes of water availability in the area during the Quaternary. The core was drilled from the Heihe alluvial fan, one of the world's largest alluvial fans, which covers a part of the Gobi Desert. Grain-size distributions supported by endmember modelling analyses, geochemical-mineralogical compositions (based on XRF and XRD measurements), and bioindicator data (ostracods, gastropods, pollen and non-pollen palynomorphs, and n-alkanes with leaf-wax delta D) are used to infer the main transport processes and related environmental changes during the Pleistocene. Magnetostratigraphy supported by radionuclide dating provides the age model. Grain- size endmembers indicate that lake, playa (sheetflood), fluvial, and aeolian dynamics are the major factors influencing sedimentation in the Ejina Basin. Core GN200 reached the pre-Quatemary quartz- and plagioclase-rich "Red Clay" formation and reworked material derived from it in the core bottom. This part is overlain by silt-dominated sediments between 217 and 110 m core depth, which represent a period of lacustrine and playa-lacustrine sedimentation that presumably formed within an endorheic basin. The upper core half between 110 and 0 m is composed of mainly silty to sandy sediments derived from the Heihe that have accumulated in a giant sediment fan until modem time. Apart from the transition from a siltier to a sandier environment with frequent switches between sediment types upcore, the clay mineral fraction is indicative of different environments. Mixed-layer clay minerals (chlorite/smectite) are increased in the basal Red Clay and reworked sediments, smectite is indicative of lacustrine-playa deposits, and increased chlorite content is characteristic of the Heihe river deposits. The sediment succession in core GN200 based on the detrital proxy interpretation demonstrates that lake-playa sedimentation in the Ejina Basin has been disrupted likely due to tectonic events in the southern part of the catchment around 1 Ma. At this time Heihe broke through from the Hexi Corridor through the Heli Shan ridge into the northern Ejina Basin. This initiated the alluvial fan progradation into the Ejina Basin. Presently the sediment bulge repels the diminishing lacustrine environment further north. In this sense, the uplift of the hinterland served as a tipping element that triggered landscape transformation in the northern Tibetan foreland (i.e. the Hexi Corridor) and further on in the adjacent northern intracontinental Ejina Basin. The onset of alluvial fan formation coincides with increased sedimentation rates on the Chinese Loess Plateau, suggesting that the Heihe alluvial fan may have served as a prominent upwind sediment source for it
Two-loop two-point functions with masses: asymptotic expansions and Taylor series, in any dimension
In all mass cases needed for quark and gluon self-energies, the two-loop
master diagram is expanded at large and small , in dimensions, using
identities derived from integration by parts. Expansions are given, in terms of
hypergeometric series, for all gluon diagrams and for all but one of the quark
diagrams; expansions of the latter are obtained from differential equations.
Pad\'{e} approximants to truncations of the expansions are shown to be of great
utility. As an application, we obtain the two-loop photon self-energy, for all
, and achieve highly accelerated convergence of its expansions in powers of
or , for .Comment: 25 pages, OUT--4102--43, BI--TP/92--5
Mass Corrections to the Tau Decay Rate
In this note radiative corrections to the total hadronic decay rate of the
-lepton are studied employing perturbative QCD and the operator product
expansion. We calculate quadratic quark mass corrections to the decay rate
ration to the order and find that they
contribute appreciably to the Cabbibo supressed decay modes of the
-lepton. We also discuss corrections of mass dimension D=4, where we
emphasize the need of a suitable choice of the renormalization scale of the
quark and gluon condensates.Comment: 13 pages, LaTeX, no figures. This version fixes a typo in eq. (25) of
the original paper (Z. Phys. C59 (1993) 525) and an errror in a numerical
integration procedure which has resulted to a significant increase of the
O(\alpha_s^2) coefficient in eq. (27). As a consequence also some tables in
Section 4 have been modifie
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