共查询到20条相似文献,搜索用时 890 毫秒
1.
M. Hauer V. V. Begun M. I. Gorenstein 《The European Physical Journal C - Particles and Fields》2008,58(1):83-110
The aim of this paper is to introduce a new technique for the calculation of observables, in particular multiplicity distributions,
in various statistical ensembles at finite volume. The method is based on Fourier analysis of the grand canonical partition
function. A Taylor expansion of the generating function is used to separate contributions to the partition function in their
power in volume. We employ Laplace’s asymptotic expansion to show that any equilibrium distribution of multiplicity, charge,
energy, etc. tends to a multivariate normal distribution in the thermodynamic limit. A Gram–Charlier expansion additionally
allows for the calculation of finite volume corrections. Analytical formulas are presented for the inclusion of resonance
decay and finite acceptance effects directly into the partition function of the system. This paper consolidates and extends
previously published results of the current investigation into the properties of statistical ensembles. 相似文献
2.
Valerio Faraoni 《The European Physical Journal C - Particles and Fields》2010,70(1-2):363-366
The t<0 branch of pre-big bang cosmological scenarios is subject to a gravitational wave instability. The unstable behaviour of tensor perturbations is derived in a very simple way in Hwang’s covariant and gauge-invariant formalism developed for extended theories of gravity. A simple interpretation of this instability as the effect of an “antifriction” is given, and it is argued that a universe must eventually enter the expanding phase. 相似文献
3.
Hye Won Kim Eun-Kyung Ahn Bo Keun Jee Hyoung-Kyu Yoon Kweon Haeng Lee Young Lim 《Journal of nanoparticle research》2009,11(1):55-65
In urban areas, the quantity of exhaust particles from vehicle emissions is tremendous and has been regarded as the main contributor
to particulate matter (PM) pollution. Recently, the nano-sized PM on public health has begun to raise the attention. The increased
toxicity of nanoparticulate can be largely explained by their small size, high airborne concentration, extensive surface area
and high content of organic carbon and transition metals. We have attempted to address the toxicity of nano sized-particlulate
matter by comparing various particulates including micro-SiO2 (mSiO2), nano-SiO2 (nSiO2), micro-TiO2 (mTiO2), and nano-TiO2 (nTiO2) in RAW264.7 cells and in vivo. The cell viability of all particulates decreased dose dependently. 24-h incubation with nSiO2
demonstrated apoptosis in RAW264.7 using Annexin-V binding immunofluorescent microscopy, but not in any other particulates.
In vivo, cytotoxicity of nanosized was higher than micro-sized particulates. As higher the concentration of particulates,
the more pulmonary injury and neutrophilic infiltration were observed in nano-sized than micro-sized particulates, respectively.
Particularly, 5.0 mg/kg of mTiO2 never shows any increase of neutrophile even with high cellularity of total cells and macrophages. From these results, we
suggested that particulate-induced respiratory toxicity be influenced by component, size, and dose of particulates including
the characteristic nature of the target cells in vitro and in vivo. 相似文献
4.
André Mischke 《The European Physical Journal C - Particles and Fields》2009,61(4):807-809
We report measurements of the azimuthal angular correlation distribution of heavy-quark decay electrons and open charmed mesons
in pp collisions at
GeV in the STAR experiment at RHIC. This measurement in combination with current theoretical model calculations allows to
extract the relative bottom contribution to the heavy-quark decay electrons, which is important for the interpretation of
the observed strong suppression of the high-p
T electron yield in central Au+Au collisions. 相似文献
5.
X. G. Kong Y. Yu T. Gao 《The European Physical Journal B - Condensed Matter and Complex Systems》2010,76(3):365-371
The ab initio pseudopotential method within the
generalized gradient approximation (GGA) and quasiparticle approximation has
been used to investigate the electronic properties of titanium dioxide in
the rutile, anatase, and fluorite structures, respectively. Here we present
the GW approximation for the electronic self-energy, which allows to
calculate excited-state properties, especially electronic band structures.
For this calculation, good agreement with the experimental results for the
minimum band gaps in rutile and anatase phase is obtained. In the fluorite
phase we predict that titanium dioxide will be an indirect (Γ to X)
wide band-gap semiconductor (2.367 or 2.369 eV) and the properties remain to
be confirmed by experiment. 相似文献
6.
Carlo Cafaro 《International Journal of Theoretical Physics》2008,47(11):2924-2933
A new information-geometric approach to chaotic dynamics on curved statistical manifolds based on Entropic Dynamics (ED) is
proposed. It is shown that the hyperbolicity of a non-maximally symmetric 6N-dimensional statistical manifold ℳ
s
underlying an ED Gaussian model describing an arbitrary system of 3N degrees of freedom leads to linear information-geometric entropy growth and to exponential divergence of the Jacobi vector
field intensity, quantum and classical features of chaos respectively. 相似文献
7.
In this paper, we study the symmetries of massless and massive particles action. By considering the non-commutative space-time,
we find appropriate non-commutative relation for relativistic particles which leaves invariant the non-commutative Minkowski
space-time. We show that non-commutativity break the scale and conformal invariance in massless and massive action. So, in
non-commutative space-time the massless and massive particles have same symmetry. 相似文献
8.
Luigi Cappiello Giancarlo D’Ambrosio 《The European Physical Journal C - Particles and Fields》2010,69(1-2):315-329
In holographic QCD the effects of gluonic condensate can be encoded in a suitable deformation of the 5D metric. We develop two different methods for the evaluation of first order perturbative corrections to masses and decay constants of vector resonances in 5D Hard-Wall models of QCD due to small deformations of the metric. They are extracted either from a novel compact form for the first order correction to the vector two-point function, or from perturbation theory for vector bound-state eigenfunctions: the equivalence of the two methods is shown. Our procedures are then applied to flat and to AdS 5D Hard-Wall models; we complement results of existing literature evaluating the corrections to vector decay constant and to two-pion–one-vector couplings: this is particularly relevant to satisfy the sum rules. We concentrate our attention on the effects for the Gasser–Leutwyler coefficients; we show that as in the Chiral Quark model, the addition of the gluonic condensate improves the consistency, the understanding and the agreement with phenomenology of the holographic model. 相似文献
9.
Xian-Qiao Yu 《The European Physical Journal C - Particles and Fields》2009,64(4):529-532
We study the nucleon electromagnetic form factors in a quark–gluon core model framework, which can be viewed as an extension
of the Isgur–Karl model of baryons. Using this picture we derive nucleon electromagnetic dipole form factors at low Q
2 and the deviation from the dipole form at high Q
2, that are consistent with the existing experimental data. 相似文献
10.
Dennis Dieks 《Foundations of Physics》2009,39(7):760-775
Pekka Lahti is a prominent exponent of the renaissance of foundational studies in quantum mechanics that has taken place during the last few decades. Among other things, he and coworkers have drawn renewed attention to, and have analyzed with fresh mathematical rigor, the threat of inconsistency at the basis of quantum theory: ordinary measurement interactions, described within the mathematical formalism by Schrödinger-type equations of motion, seem to be unable to lead to the occurrence of definite measurement outcomes, whereas the same formalism is interpreted in terms of probabilities of precisely such definite outcomes. Of course, it is essential here to be explicit about how definite measurement results (or definite properties in general) should be represented in the formalism. To this end Lahti et al. have introduced their objectification requirement that says that a system can be taken to possess a definite property if it is certain (in the sense of probability 1) that this property will be found upon measurement. As they have gone on to demonstrate, this requirement entails that in general definite outcomes cannot arise in unitary measuring processes.In this paper we investigate whether it is possible to escape from this deadlock. As we shall argue, there is a way out in which the objectification requirement is fully maintained. The key idea is to adapt the notion of objectivity itself, by introducing relational or perspectival properties. It seems that such a “relational perspective” offers prospects of overcoming some of the long-standing problems in the interpretation of quantum mechanics. 相似文献
11.
Z. Fleischman C. Munasinghe A. J. Steckl A. Wakahara J. Zavada V. Dierolf 《Applied physics. B, Lasers and optics》2009,97(3):607-618
Using combined excitation emission spectroscopy, we performed a comparative study of europium ions in GaN in samples that
have been in situ doped during interrupted growth epitaxy (IGE) or conventional molecular beam epitaxy (MBE) as well as samples
that were grown using organometallic vapor phase epitaxy (OMVPE) and subsequently ion implanted with Eu ions. Through site-selective
resonant excitation, we are able to unambiguously assign all major observed transitions to a combination of different incorporation
sites and electron–phonon coupled transitions. We identified at least nine different incorporation sites of Eu ions in GaN
and studied how these sites behave under different excitation conditions and how their relative number is modified by different
growth and doping conditions. The coupling to phonons has also been studied for a series of Al
x
Ga1−x
N samples with x=0…1. We find that a main site most resembling an unperturbed Eu ion on Ga site is always dominant, while the minority sites
are changing substantially in relative numbers and can occur in some samples fairly close in emission intensity to the main
site. In terms of the excitation pathway after the creation of electron-hole pairs, we found three types of centers: (1) sites
that are dominantly excited through shallow defect traps; (2) sites that are excited through a deep defect trap; (3) sites
that cannot be excited at all including the majority of the main sites. We interpret this finding to indicate that the ion
in this environment is not very efficient in trapping excitation and that the indirect excitation involving other traps depends
on the ion/trap distance. Many of the main sites are far away from these traps and cannot be excited through this channel
at all. The efficiency of excitation is highest for the deep traps, indicating that it would be desirable to enrich the respective
site, as has been done with some success in the IGE grown samples. 相似文献
12.
The radiative transition form factors of the pseudoscalar mesons π, η, η′ and the vector mesons ρ, ω, φ are restudied with π–η–η′ and ρ–ω–φ in the tri-meson-mixing pattern, which is described by tri-mixing matrices in the light-cone constituent quark model. The experimental transition decay widths are better reproduced with tri-meson mixing than previous results in a two-mixing-angle scenario of only two-meson η–η′ mixing and ω–φ mixing. 相似文献
13.
R. S. Kolevatov 《The European Physical Journal C - Particles and Fields》2010,68(3-4):513-521
A fragmenting relativistic string is widely used for modeling particle production via quark–gluon strings formed in hadronic and nuclear inelastic interactions at high energies. In this note we focus on motion and fragmentation of a relativistic string with non-zero transverse separation of its ends and study this scenario as a possible mechanism for bringing anisotropy into the azimuthal angle distribution of produced particles in inelastic interactions of hadrons. 相似文献
14.
Lawrence Dunn Brian Cobb Dharmendar Reddy Ananth Dodabalapur 《Applied Physics A: Materials Science & Processing》2009,95(1):153-158
In this paper we describe three methods that can be used to measure the transient response of organic and polymer field-effect
transistors (FETs) and also how such measurements can be used to determine the drift mobility and velocity. The first method
measures the response of a FET to a step voltage applied to the source with the gate grounded and the drain held at close
to ground, while the second uses a ramp input to the source. The third technique evaluates the frequency response of the FET,
connected as a diode, to a large-signal alternating voltage. We show that important information can be obtained from such
measurements which can be quantitatively interpreted with the help of models that we are developing. In general, there is
good agreement between the drift mobility measured with these approaches and the field-effect mobility calculated from transistor
output and transfer characteristics. The specific results we present in this paper are for pentacene devices; however, other
recent work by our group indicates that these results are more general. 相似文献
15.
Anna De Masi Immacolata Merola Errico Presutti Yvon Vignaud 《Journal of statistical physics》2009,134(2):243-306
This is the second of two papers on a continuum version of the Potts model, where particles are points in ℝ
d
, d≥2, with a spin which may take S≥3 possible values. Particles with different spins repel each other via a Kac pair potential of range γ
−1, γ>0. In this paper we prove phase transition, namely we prove that if the scaling parameter of the Kac potential is suitably
small, given any temperature there is a value of the chemical potential such that at the given temperature and chemical potential
there exist S+1 mutually distinct DLR measures. 相似文献
16.
Daniel Charbulák Zdeněk Stuchlík 《The European Physical Journal C - Particles and Fields》2017,77(12):897
We study the general motion of photons in the Kerr–de Sitter black-hole and naked singularity spacetimes. The motion is governed by the impact parameters X, related to the axial symmetry of the spacetime, and q, related to its hidden symmetry. Appropriate ‘effective potentials’ governing the latitudinal and radial motion are introduced and their behavior is examined by the ‘Chinese boxes’ technique giving regions allowed for the motion in terms of the impact parameters. Restrictions on the impact parameters X and q are established in dependence on the spacetime parameters \(M, \Lambda , a\). The motion can be of orbital type (crossing the equatorial plane, \(q>0\)) and vortical type (tied above or below the equatorial plane, \(q<0\)). It is shown that for negative values of q, the reality conditions imposed on the latitudinal motion yield stronger constraints on the parameter X than that following from the reality condition of the radial motion, excluding the existence of vortical motion of constant radius. The properties of the spherical photon orbits of the orbital type are determined and used along with the properties of the effective potentials as criteria of classification of the KdS spacetimes according to the properties of the motion of the photon. 相似文献
17.
Christian?G.?B?hmer Francisco?S.?N.?Lobo 《The European Physical Journal C - Particles and Fields》2010,70(4):1111-1118
Recently, Hořava proposed a power counting renormalizable theory for (3+1)-dimensional quantum gravity, which reduces to Einstein
gravity with a non-vanishing cosmological constant in IR, but possesses improved UV behaviors. In this work, we analyze the
stability of the Einstein static universe by considering linear homogeneous perturbations in the context of an IR modification
of Hořava gravity, which implies a ‘soft’ breaking of the ‘detailed balance’ condition. The stability regions of the Einstein
static universe is parameterized by the linear equation of state parameter w=p/ρ and the parameters appearing in the Hořava theory, and it is shown that a large class of stable solutions exists in the respective
parameter space. 相似文献
18.
We study the Generalized Brans-Dicke cosmology in the presence of matter and dark energy. Of particular interest for a constant
Brans-Dicke parameter, the de Sitter space has also been investigated. 相似文献
19.
The study of superconductivity, dual superconductivity and color superconductivity has been undertaken through the breaking
of super symmetric gauge theory in restricted chromo dynamics (RCD) which automatically incorporates the condensation of monopoles
and dyons leading to confining and superconducting phases. Dyonic supermultiplets in N=1 super symmetry have been obtained quantum mechanically in RCD and it has been shown that dyon appears in RCD theory only
through restricted part of the generalized potential and it is only this part of this potential which is responsible for quark
confinement and the resulting superconductivity through the mechanism of dyonic condensation. 相似文献
20.
Alexandre Mermillod-Blondin Euan McLeod Craig B. Arnold 《Applied Physics A: Materials Science & Processing》2008,93(1):231-234
The ability to dynamically shape the spatial intensity profile of an incident laser beam enables new ways to modify and structure
surfaces through pulsed laser processing. Here we describe a method to generate doughnut-shaped beams from an input Gaussian
source using a tunable acoustic gradient index (TAG) lens. The TAG lens is capable of modulating between focused beams and
annular rings of variable size, using sinusoidal driving frequencies. Laser micromachining is accomplished by synchronizing
the TAG lens to a 355 nm pulsed nanosecond laser. Results in polyimide demonstrate the ability to generate adjacent surface
features with different shapes and sizes. 相似文献