3,482 research outputs found
Significant Conditions on the Two-electron Reduced Density Matrix from the Constructive Solution of N-representability
We recently presented a constructive solution to the N-representability
problem of the two-electron reduced density matrix (2-RDM)---a systematic
approach to constructing complete conditions to ensure that the 2-RDM
represents a realistic N-electron quantum system [D. A. Mazziotti, Phys. Rev.
Lett. 108, 263002 (2012)]. In this paper we provide additional details and
derive further N-representability conditions on the 2-RDM that follow from the
constructive solution. The resulting conditions can be classified into a
hierarchy of constraints, known as the (2,q)-positivity conditions where the q
indicates their derivation from the nonnegativity of q-body operators. In
addition to the known T1 and T2 conditions, we derive a new class of
(2,3)-positivity conditions. We also derive 3 classes of (2,4)-positivity
conditions, 6 classes of (2,5)-positivity conditions, and 24 classes of
(2,6)-positivity conditions. The constraints obtained can be divided into two
general types: (i) lifting conditions, that is conditions which arise from
lifting lower (2,q)-positivity conditions to higher (2,q+1)-positivity
conditions and (ii) pure conditions, that is conditions which cannot be derived
from a simple lifting of the lower conditions. All of the lifting conditions
and the pure (2,q)-positivity conditions for q>3 require tensor decompositions
of the coefficients in the model Hamiltonians. Subsets of the new
N-representability conditions can be employed with the previously known
conditions to achieve polynomially scaling calculations of ground-state
energies and 2-RDMs of many-electron quantum systems even in the presence of
strong electron correlation
Exactly solvable models in 2D semiclassical dilaton gravity and extremal black holes
Previously known exactly solvable models of 2D semiclassical dilaton gravity
admit, in the general case, only non-extreme black holes. It is shown that
there exist exceptional degenerate cases, that can be obtained by some limiting
transitions from the general exact solution, which include, in particular,
extremal and ultraextremal black holes. We also analyze properties of extreme
black holes without demanding exact solvability and show that for such
solutions quantum backreaction forbids the existence of ultraextreme black
holes. The conditions,under which divergencies of quantum stresses in a free
falling frame can disappear, are found. We derive the closed equation with
respect to the metric as a function of the dilaton field that enables one,
choosing the form of the metric, to restore corresponding Lagrangian. It is
demonstrated that exactly solvable models, found earlier, can be extended to
include an electric charge only in two cases: either the dilaton-gravitation
coupling is proportional to the potential term, or the latter vanishes. The
second case leads to the effective potential with a negative amplitude and we
analyze, how this fact affects the structure of spacetime. We also discuss the
role of quantum backreaction in the relationship between extremal horizons and
the branch of solutions with a constant dilaton.Comment: 31 pages. In v.2 typo in Ref. [2] corrected, 4 references added.
Accepted in Class. Quant. Gra
Generalized 2d dilaton gravity with matter fields
We extend the classical integrability of the CGHS model of 2d dilaton gravity
[1] to a larger class of models, allowing the gravitational part of the action
to depend more generally on the dilaton field and, simultaneously, adding
fermion- and U(1)-gauge-fields to the scalar matter. On the other hand we
provide the complete solution of the most general dilaton-dependent 2d gravity
action coupled to chiral fermions. The latter analysis is generalized to a
chiral fermion multiplet with a non-abelian gauge symmetry as well as to the
(anti-)self-dual sector df = *df (df = -*df) of a scalar field f.Comment: 37 pages, Latex; typos and Eqs. (44,45) corrected; paragraph on p.
26, referring to a work of S. Solodukhin, reformulated; references adde
Система управления персоналом организации на примере обувной сети «Дарина»
Выпускная квалификационная работа 72 с., 5 рис., 13 табл., 40 источников, 3 прил.
Ключевые слова: система управления персоналом, персонал, кадры, модели управления персоналом, система стимулирования.
Объект исследования – обувная сеть «Дарина».
Предмет исследования – предложения по совершенствованию системы управления персоналом в сети магазинов «Дарина».
Цель работы – на основе анализа системы управления персоналом в сети магазинов «Дарина» разработать предложения по ее совершенствованию.Graduation thesis 72 p., 5 Fig., 13 tab., 40 sources, 3 ADJ.
Key words: personnel management system, personnel, personnel, model of personnel management, system of incentives.
The object of study – Shoe network "Darina".
Subject of research – proposals for improving the personnel management system in chain stores "Darina".
Purpose – based on the analysis of the personnel management system in chain stores "Darina" to develop proposals for its improvement
Quantum magneto-oscillations in a two-dimensional Fermi liquid
Quantum magneto-oscillations provide a powerfull tool for quantifying
Fermi-liquid parameters of metals. In particular, the quasiparticle effective
mass and spin susceptibility are extracted from the experiment using the
Lifshitz-Kosevich formula, derived under the assumption that the properties of
the system in a non-zero magnetic field are determined uniquely by the
zero-field Fermi-liquid state. This assumption is valid in 3D but, generally
speaking, erroneous in 2D where the Lifshitz-Kosevich formula may be applied
only if the oscillations are strongly damped by thermal smearing and disorder.
In this work, the effects of interactions and disorder on the amplitude of
magneto-oscillations in 2D are studied. It is found that the effective mass
diverges logarithmically with decreasing temperature signaling a deviation from
the Fermi-liquid behavior. It is also shown that the quasiparticle lifetime due
to inelastic interactions does not enter the oscillation amplitude, although
these interactions do renormalize the effective mass. This result provides a
generalization of the Fowler-Prange theorem formulated originally for the
electron-phonon interaction.Comment: 4 pages, 1 figur
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