1,778 research outputs found
Incoherent quantum feedback control of collective light scattering by Bose-Einstein condensates
It is well known that in the presence of a ring cavity the light scattering
from a uniform atomic ensemble can become unstable resulting in the collective
atomic recoil lasing. This is the result of a positive feedback due to the
cavity. We propose to add an additional electronic feedback loop based on the
photodetection of the scattered light. The advantage is a great flexibility in
choosing the feedback algorithm, since manipulations with electric signals are
very well developed. In this paper we address the application of such a
feedback to atoms in the Bose-Einstein condensed state and explore the quantum
noise due to the incoherent feedback action. We show that although the feedback
based on the photodetection does not change the local stability of the initial
uniform distribution with respect to small disturbances, it reduces the region
of attraction of the uniform equilibrium. The feedback-induced nonlinearity
enables quantum fluctuations to bring the system out of the stability region
and cause an exponential growth even if the uniform state is globally stable
without the feedback. Using numerical solution of the feedback master equation
we show that there is no feedback-induced noise in the quadratures of the
excited atomic and light modes. The feedback loop, however, introduces
additional noise into the number of quanta of these modes. Importantly, the
feedback opens an opportunity to position the modulated BEC inside a cavity as
well as tune the phase of scattered light. This can find applications in
precision measurements and quantum simulations.Comment: 7 pages, 7 figure
A combinatorial approach to the set-theoretic solutions of the Yang-Baxter equation
A bijective map , where
is a finite set, is called a \emph{set-theoretic solution of the Yang-Baxter
equation} (YBE) if the braid relation
holds in A non-degenerate involutive solution satisfying
, for all , is called \emph{square-free solution}. There
exist close relations between the square-free set-theoretic solutions of YBE,
the semigroups of I-type, the semigroups of skew polynomial type, and the
Bieberbach groups, as it was first shown in a joint paper with Michel Van den
Bergh.
In this paper we continue the study of square-free solutions and the
associated Yang-Baxter algebraic structures -- the semigroup , the
group and the - algebra over a field , generated by
and with quadratic defining relations naturally arising and uniquely
determined by . We study the properties of the associated Yang-Baxter
structures and prove a conjecture of the present author that the three notions:
a square-free solution of (set-theoretic) YBE, a semigroup of I type, and a
semigroup of skew-polynomial type, are equivalent. This implies that the
Yang-Baxter algebra is Poincar\'{e}-Birkhoff-Witt type algebra,
with respect to some appropriate ordering of . We conjecture that every
square-free solution of YBE is retractable, in the sense of Etingof-Schedler.Comment: 34 page
Higher education market in Ukraine
The article analyses key features o f how the higher education market develops in Ukraine. In order to cover the topic on a large scale, we have defined the terms o f education sen’ice and sen’ice differentiation. The analysis o f market structure gives reasons for stating that the higher education market in Ukraine acts under the conditions o f monopolistic competition.У статті розглянуто загальні характеристики розвитку ринку освітніх послуг України. З метою розкриття теми було визначено поняття «освітня послуга» та «диференціація послуги». Аналіз структури ринку дає підстави характеризувати ргінок освітніх послуг України як монополістичну конкуренцію
Хлорфенолы в органическом синтезе
Received: 17.08.2016; accepted: 11.10.2016; published: 01.12.2016.Поступило: 17.08.2016; приянято: 11.10.2016; опубликовано: 01.12.2016.This article reviews the alternatives for modifications of p-chlorophenols, p-chloroanisoles with the formation of C-C, C-N, C-S and C-B bonds. It is worth noting the high fundamental as well as practical importance of these reactions due to the availability and cheapness of initial chlorine substituted derivatives of phenol.В данном обзоре рассмотрены варианты модификаций п-хлорфенолов и п-хлоранизолов с образованием связей C-C, C-N, C-S и C-B. Стоит отметить высокую не только фундаментальную, но и практическую значимость данных реакций, ввиду доступности и дешевизны исходных хлорзамещенных производных фенола
First investigation of noble gases in the Dengli H3,8 chondrite
The Dengli (H3,8) meteorite, which weighs 243.5 g, is a find from the Karakum desert. It is a complex microbreccia containing unusual clasts which are more typical for regolithic breccias than for H-chondrites. Based on comparisons of Xe and Kr content and isotopic composition, the Dengli does not differ significantly from other H-chondrites. Its exposure age is 7.6 Ma. That is in agreement with common data for the exposure age (6.2 + 0.2 Ma) of 350 H-chondrites. Dengli's K/Ar age (4.01 Ga) coincides with the same ages of many other H-chondrites. Thus the Dengli is not regolithic breccia, and it probably formed during accretion of its parent body
BENZ- AND HETARENE-ANNULATED AZEPINES FROM DONOR-ACCEPTOR CYCLOPROPANES
This work was supported by Russian Science Foundation (grant № 18-13-00449
Дискуссия по проблеме субъекта в современном феминизме
In article are considered the concept of “subject”, “women's subjectivity”, “nomadic subjectivity”, “identity”, “feminism”.В статье рассматриваются понятия “субъект”, “женская субъективность”, “номадическая субъективность”, “идентичность”, “феминизм”
THE PHENOMENON OF ALIENATION IN CHILDREN-PARENT RELATIONS
The main approaches to the definition of the phenomenon of “alienation” have been considered. The causes and dynamics of the emergence of alienation in the child-parent relationship have been investigated. Interconnection of violations in parent-child relationships with the incorrect educational strategy of parents has been revealed. Special attention has been paid to the specificity of manifestations and the nature of alienation in adolescence. It has been supposed about the connection between alienation and style of upbringing of a teenager. The practical part of the article describes the procedure and results of the study on the determination of this connection. The analysis has identified a statistically significant interrelation between alienation and the relationship between parents and children. Critical importance of hypo-care for the formation of teenage alienation has been ascertained. The characteristic of child-parent relations in same-sex and opposite-sex couples child-parent has been made
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