4,335 research outputs found
Paramagnetic-diamagnetic interplay in quantum dots for non-zero temperatures
In the usual Fock-and Darwin-formalism with parabolic potential characterized
by the confining energy \eps_o := \hbar\omega_o= 3.37 meV, but including
explicitly also the Zeeman coupling between spin and magnetic field, we study
the combined orbital and spin magnetic properties of quantum dots in a
two-dimensional electron gas with parameters for GaAs, for N =1 and N >> 1
electrons on the dot.
For N=1 the magnetization M(T,B) consists of a paramagnetic spin contribution
and a diamagnetic orbital contribution, which dominate in a non-trivial way at
low temperature and fields rsp. high temperature and fields.
For N >> 1, where orbital and spin effects are intrinsically coupled in a
subtle way and cannot be separated, we find in a simplified Hartree
approximation that at N=m^2, i.e. at a half-filled last shell, M(T,B,N) is
parallel (antiparallel) to the magnetic field, if temperatures and fields are
low enough (high enough), whereas for N\ne m^2 the magnetization oscillates
with B and N as a T-dependent periodic function of the variable
x:=\sqrt{N}eB/(2m^*c\omega_o), with T-independent period \Delta x =1 (where m^*
:= 0.067 m_o is the small effective mass of GaAs, while m_o is the electron
mass). Correspondingly, by an adiabatic demagnetization process, which should
only be fast enough with respect to the slow transient time of the magnetic
properties of the dot, the temperature of the dot diminishes rsp. increases
with decreasing magnetic field, and in some cases we obtain quite pronounced
effects.Comment: LaTeX, 28 pages; including three .eps-figures; final version accepted
by J. Phys. CM, with minimal changes w.r.to v
Implementation of the Multiple Point Principle in the Two-Higgs Doublet Model of type II
The multiple point principle (MPP) is applied to the non--supersymmetric
two-Higgs doublet extension of the Standard Model (SM). The existence of a
large set of degenerate vacua at some high energy scale caused by the MPP
results in a few relations between Higgs self-coupling constants which can be
examined at future colliders. The numerical analysis reveals that these MPP
conditions constrain the mass of the SM--like Higgs boson to lie below 180 GeV
for a wide set of MPP scales and .Comment: 26 pages, 3 figures, some minor changes to the tex
The Pulsar Wind Nebula Around PSR B1853+01 in the Supernova Remnant W44
We present radio observations of a region in the vicinity of the young pulsar
PSR B1853+01 in the supernova remnant W44. The pulsar is located at the apex of
an extended feature with cometary morphology. We argue on the basis of its
morphology and its spectral index and polarization properties that this is a
synchrotron nebula produced by the spin down energy of the pulsar. The geometry
and physical parameters of this pulsar-powered nebula and W44 are used to
derive three different measures of the pulsar's transverse velocity. A range of
estimates between 315 and 470 km/s are derived, resulting in a typical value of
375 km/s. The observed synchrotron spectrum from radio to X-ray wavelengths is
used to put constraints on the energetics of the nebula and to derive the
parameters of the pulsar wind.Comment: ApJ Let (in press
An integrative approach based on probabilistic modelling and statistical inference for morpho-statistical characterization of astronomical data
This paper describes several applications in astronomy and cosmology that are
addressed using probabilistic modelling and statistical inference
МЕТОДИЧНИЙ ПІДХІД ДО ОЦІНКИ РІВНЯ ФІНАНСОВОЇ БЕЗПЕКИ БУДІВЕЛЬНОГО ПІДПРИЄМСТВА
The article deals with the issues of assessing the level of a construction company financial security. It is determined that the specificity of the construction enterprises activity and their diverse financial relations system require the formation of an appropriate system for certain financial interests protection against existing and potential internal and external threats, that is reflected in the approaches to the definition of “enterprise financial security”. The system of an enterprise financial security is proposed and the existing methodical approaches to assessing the level of enterprise financial security are generalized. The methodical approach to assessing the level of construction company financial security on the example of JSC “Trust Zhytlobud-1” is developed, which allows to distinguish factors-indicators that influence that level, to rank them and to calculate the integral indicator of financial security, which determines its level. As a result of the assessment it was determined that Economic crisis in Ukraine 2013—2014 caused a fall in the level of JSC “Trust Zhytlobud-1” financial security, but the successful financial policy of the company management led to a substantial increase in the financial security level. The application of the proposed methodological approach to assessing the level of a construction company financial security will enable the enterprises management to respond in a timely manner to the deterioration of the economic entity financial condition as well as the negative trends that may develop in the course of the business entity’s activity.Исследован вопрос оценки уровня финансовой безопасности строительного предприятия. Установлено, что специфика деятельности строительных предприятий и наличие в них разнообразной системы финансовых отношений требует формирования соответствующей системы защиты определенных финансовых интересов от существующих и потенциальных угроз внутренней и внешней среды, что отражается в подходах к определению понятия «финансовая безопасность предприятия». Предложена система экономической безопасности предприятия и обобщены существующие методические подходы к оценке уровня финансовой безопасности предприятия. Разработан методический подход к оценке уровня финансовой безопасности строительного предприятия на примере АО «Трест Жилстрой-1», который позволяет выделить факторы-индикаторы, влияющие на уровень финансовой безопасности строительного предприятия, ранжировать их и вычислить интегральный показатель финансовой безопасности, по которому устанавливается ее уровень. В результате оценки установлено, что экономический кризис в Украине в 2013—2014 гг. обусловил падение уровня финансовой безопасности АО «Трест Жилстрой-1», но удачная финансовая политика руководства предприятия привела к повышению уровня финансовой безопасности к достаточно высокому. Использование предложенного методического подхода к оценке уровня финансовой безопасности строительного предприятия дает возможность для менеджмента предприятий вовремя среагировать на ухудшение финансового состояния субъекта хозяйствования и негативные тенденции, которые могут развиваться в процессе деятельности хозяйствующего субъекта.Досліджено питання оцінки рівня фінансової безпеки будівельного підприємства. Установлено, що специфіка діяльності будівельних підприємств і наявність у них різноманітної системи фінансових відносин вимагає формування відповідної системи захисту певних фінансових інтересів від наявних і потенційних загроз внутрішнього і зовнішнього середовища, що відображається у підходах до визначення поняття «фінансова безпека підприємства». Запропоновано систему фінансової безпеки підприємства та узагальнено наявні методичні підходи до оцінки рівня фінансової безпеки підприємства. Розроблено методичний підхід до оцінки рівня фінансової безпеки будівельного підприємства на прикладі АТ «Трест Житлобуд-1», який дозволяє виокремити фактори-індикатори, що мають вплив на рівень фінансової безпеки будівельного підприємства, ранжирувати їх та обчислити інтегральний показник фінансової безпеки, за яким встановлюється її рівень. У результаті оцінки встановлено, що економічна криза в Україні у 2013—2014 роках зумовила падіння рівня фінансової безпеки АТ «Трест Житлобуд-1», але вдала фінансова політика керівництва підприємства призвела до підвищення рівня фінансової безпеки до достатньо високого. Використання запропонованого методичного підходу до оцінки рівня фінансової безпеки будівельного підприємства надасть можливість менеджментові підприємств вчасно зреагувати на погіршення фінансового стану суб’єкта господарювання і негативні тенденції, що можуть розвиватися у процесі діяльності суб’єкта господарювання
Phase transition in gauge theories, monopoles and the Multiple Point Principle
This review is devoted to the Multiple Point Principle (MPP), according to
which several vacuum states with the same energy density exist in Nature. The
MPP is implemented to the Standard Model (SM), Family replicated gauge group
model (FRGGM) and phase transitions in gauge theories with/without monopoles.
Lattice gauge theories are reviewed. The lattice results for critical coupling
constants are compared with those of the Higgs Monopole Model (HMM), in which
the lattice artifact monopoles are replaced by the point-like Higgs scalar
particles with a magnetic charge. Considering our (3+1)-dimensional space-time
as discrete, for example, as a lattice with a parameter a=\lambda_P, equal to
the Planck length, we have investigated the additional contributions of
monopoles to beta-functions of renormalization group equations in the FRGGM
extended beyond the SM at high (the Planck scale) energies. We have reviewed
that, in contrast to the Anti-grand unified theory (AGUT), there exists a
possibility of unification of all gauge interactions (including gravity) near
the Planck scale due to monopoles. The unifications [SU(5)]^3 and [SO(10)]^3 at
the GUT-scale \sim 10^{18} GeV are briefly discussed.Comment: 100 pages, 25 figures, typos correcte
The role of ecological groups in the formation of cyanobacterial communities in the ecosystems of the North Azov region (Ukraine)
The role of Cyanoprokaryota ecological groups in the ecosystems of the North Azov region was revealed in this work. On the territory of Pryazovskyi National Nature Park, 9 experimental polygons were studied, which covered steppe areas or slopes, salt marshes, coastal sandy soils and water bodies (rivers, lakes, estuaries, sea bays, lagoons). As a result of research on the territory of Pryazovskyi National Nature Park, 124 species of cyanoprokaryotes were identified, which include 127 intraspecific taxa. It was proved that the procedure of canonical correspondence analysis is the most suitable for the analysis of the species matrix. The axes identified as a result of the ordination procedure, which indicate the coordinated dynamics of the species, correlated with both synecological characteristics, such as diversity indicators, and with autoecological characteristics, such as ecotypes of cyanoprokaryotes in relation to habitat types or types of adaptation to salinity conditions. The first four canonical axes together explain 47.5% of species matrix variability. Canonical axis 1 explains 18.0% of the variability of the species matrix and is mostly marked by aqual subaerophytes and eurybionts. This axis indicates the presence of a gradient of salinity conditions where the most saline conditions correspond to the positive values of the axis, and the negative values correspond to less saline. Canonical axis 2 describes 12.1% of species matrix variability. This axis differentiates aquatic ecosystems from others. Canonical axis 3 explains 10.0% of the communities’ variability. This axis distinguishes freshwater ecosystems from saline ecosystems. Markers of freshwater communities are stenotopic halotolerants, which are narrow-range, common mainly in the temperate zone of Europe. The canonical axis 4 explains 7.3% of variability of the matrix of species and is able to differentiate sand ecosystems. The ecotopic structure and geographic range width of community species have the greatest independent value among the considered sources of variation. The independent role of adaptation to the salinity conditions of the ecotope and the role of the type of ecosystems is somewhat smaller. The interaction between the sources of variation is important in the variation of the structure of communities. The interaction between the ecotopic structure and the geographic range width of species and the triple interaction between the ecotopic structure of a community, the width of the geographic range of species and the ecosystem type plays the greatest role in the variation of community structure. Ecotopic groups, which indicate the preference of a particular habitat, correlate with the species composition of the communities. It is shown that the ratio of ecototopic groups in a community is a characteristic that reveals the features of the community as a whole
Monopoles near the Planck Scale and Unification
Considering our (3+1)-dimensional space-time as, in some way, discrete or l
attice with a parameter , where is the Planck length,
we have investigated the additional contributions of lattice artifact monopoles
to beta-functions of the renormalisation group equations for the running fine
structure constants (i=1,2,3 correspond to the U(1), SU(2) and
SU(3) gauge groups of the Standard Model) in the Family Replicated Gauge Group
Model (FRGGM) which is an extension of the Standard Model at high energies. It
was shown that monopoles have times smaller magnetic charge in FRGGM
than in SM ( is the number of families in FRGGM). We have estimated al
so the enlargement of a number of fermions in FRGGM leading to the suppression
of the asymptotic freedom in the non-Abelian theory. We have shown that, in
contrast to the case of AntiGUT when the FRGGM undergoes the breakdown at
GeV, we have the possibility of unification if the
FRGGM-breakdown occurs at GeV. By numerical calculations we
obtained an example of the unification of all gauge interactions (including
gravity) at the scale GeV. We discussed the
possibility of or (SUSY or not SUSY) unifications.Comment: 49 pages, 7 figure
- …