共查询到20条相似文献,搜索用时 343 毫秒
1.
F. Clementi M. Gallegati G. Kaniadakis 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,57(2):187-193
Starting from the generalized exponential function
, with exp 0(x)=exp (x), proposed in reference [G. Kaniadakis, Physica A 296, 405 (2001)], the survival function P>(x)=exp κ(-βxα), where x∈R+, α,β>0, and
, is considered in order to analyze the data on personal income distribution for Germany, Italy, and the United Kingdom. The
above defined distribution is a continuous one-parameter deformation of the stretched exponential function P>
0(x)=exp (-βxα)
to which reduces as κ approaches zero
behaving in very different way in the x→0 and x→∞ regions. Its bulk is very close to the stretched exponential one, whereas
its tail decays following the power-law P>(x)∼(2βκ)-1/κx-α/κ. This makes the κ-generalized function particularly suitable to describe simultaneously the income distribution among both
the richest part and the vast majority of the population, generally fitting different curves. An excellent agreement is found
between our theoretical model and the observational data on personal income over their entire range. 相似文献
2.
Zhi-Gang Wang 《The European Physical Journal C - Particles and Fields》2009,61(2):321-329
We calculate the masses and the pole residues of the
heavy baryons Ω
c
0(css) and Ω
b
−(bss) with the QCD sum rules. The numerical values
GeV (or
GeV) and
GeV (or
GeV) are in good agreement with the experimental data. 相似文献
3.
H. Prakash P. Kumar 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2008,46(2):359-363
We study amplitude-squared squeezing of the Hermitian operator Zθ=Z1
cosθ+Z2 sin θ, in the most general superposition state
, of two coherent states
and
. Here operators Z1,2 are defined by
, a is annihilation operator, θ is angle, and
complex numbers C1,2 , α, β are arbitrary and only
restriction on these is the normalization condition of the state
. We define the condition for a state
to be amplitude-squared squeezed for the operator Zθ
if squeezing parameter
, where N=a+a and
. We find
maximum amplitude-squared squeezing of Zθ in the superposed
coherent state
with minimum value 0.3268 of the
parameter S for an infinite combinations with α- β= 2.16
exp [±i(π/4) + iθ/2],
and with
arbitrary values of (α+β) and θ. For this minimum
value of squeezing parameter S, the expectation value of photon number can
vary from the minimum value 1.0481 to infinity. Variations of the parameter
S with different variables at maximum amplitude-squared squeezing are also
discussed. 相似文献
4.
Zhi-Qing Zhang Zhen-Jun Xiao 《The European Physical Journal C - Particles and Fields》2009,59(1):49-66
We calculate the important next-to-leading-order (NLO) contributions to the B→KK
* decays from the vertex corrections, the quark loops, and the magnetic penguins in the perturbative QCD (pQCD) factorization
approach. The pQCD predictions for the CP-averaged branching ratios are
,
,
and Br(B
0→K
+
K
*−+K
−
K
*+)≈1.3×10−7, which agree well with both the experimental upper limits and the predictions based on the QCD factorization approach. Furthermore,
the CP violating asymmetries of the considered decay modes are also evaluated. The NLO pQCD predictions for
and
decays are
and
. 相似文献
5.
M. Weis P. Bartsch D. Baumann J. Bermuth A. M. Bernstein K. Bohinc R. Böhm M. Ding M. O. Distler I. Ewald J. M. Friedrich J. Friedrich M. Kahrau M. Kohl K. W. Krygier A. Liesenfeld H. Merkel P. Merle U. Müller R. Neuhausen M. M. Pavan Th. Pospischil M. Potokar G. Rosner H. Schmieden M. Seimetz S. Širca A. Wagner Th. Walcher 《The European Physical Journal A - Hadrons and Nuclei》2008,38(1):27-33
The differential cross-sections σ0 = σT + εσL , σLT , and σTT of electroproduction from the proton were measured from threshold up to an additional center-of-mass energy of 40MeV, at a value
of the photon four-momentum transfer of Q
2 = 0.05 GeV2/c2 and a center-of-mass angle of θ = 90° . By an additional out-of-plane measurement with polarized electrons σLT' was determined. This showed for the first time the presence of an imaginary part of the s -wave above the threshold, which is usually interpreted as a unitary cusp. The predictions of the Heavy Baryon Chiral Perturbation Theory
(HBChPT) are in disagreement with these data. On the other hand, the data are somewhat better predicted by the MAID phenomenological
model and are in good agreement with the dynamical model DMT. 相似文献
6.
A. Ehresmann W. Kielich L. Werner Ph. V. Demekhin D. V. Omel''yanenko V. L. Sukhorukov K.-H. Schartner H. Schmoranzer 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,45(2):235-246
Dispersed fluorescence from fragments formed after the de-excitation of the
1s-1π* resonances of N*O and NO* has been
measured in the spectral range of 118–142 nm. This range is dominated by
lines of atomic nitrogen and oxygen fragments and by the
bands in the NO+ ion which result from the participator Auger decay of the 1s-1π* resonances.
Ab-initio calculations of the transition probabilities between vibrational
levels during the reaction NO
N*O
⇒ NO
were used to explain the observed intensity dependence for the
fluorescence bands on the exciting-photon energy across
the resonances and on both v′ and v′′
vibrational quantum numbers. The multiplet structure of the 1s-1π* resonance and lifetime vibrational interference explain the observed exciting-photon energy dependence of the
fluorescence
intensity. A strong spin-orbit coupling between singlet and triplet states
of NO+ is proposed to reduce additional cascade population of the
state via radiative transitions from the
and
states and to explain
remaining differences between measured and calculated integral fluorescence
intensities. 相似文献
7.
A. Nadeem M. Nawaz S. U. Haq S. Shahzada M. A. Baig 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2009,53(2):147-151
We report term energies and quantum defects of highly excited even-parity states of mercury in the 83 876–84 140 cm-1 energy range, employing a two-step laser excitation scheme via the S0↦6s6p3P1 inter-combination transition. Two dye lasers, pumped by a common Nd:YAG laser, were frequency doubled by BBO crystals and
used to record the spectra in conjunction with a thermionic diode ion detector. Our new observations include the much extended
D2 (22 ≤n ≤52) series and a few members of the S1 (24 ≤n ≤30) Rydberg series. Members of the D2 Rydberg series with such a high n value are reported for the first time. The relative intensities of the D2 and S1 transitions (m = 4, 5 and 6) of group II-B elements excited from the P1 inter-combination states are also discussed. 相似文献
8.
S.S. Agaev M.A. Gomshi Nobary 《The European Physical Journal C - Particles and Fields》2008,54(2):219-229
Power-suppressed corrections arising from end-point integration regions to the space-like vertex function of the massive η′-meson virtual gluon transition are computed. Calculations are performed within the standard hard-scattering approach (HSA) and the running coupling method
supplemented by the infrared renormalon calculus. Contributions to the vertex function from the quark and gluon contents of
the η′-meson are taken into account and the Borel resummed expressions for (Q2,ω,η), as well as for (Q2,ω=±1,η) and (Q2,ω=0,η) are obtained. It is demonstrated that the power-suppressed corrections ∼(Λ2/Q2)n, in the explored range of the total gluon virtuality 1≤Q2≤25 GeV2, considerably enhance the vertex function relative to the results found in the framework of the standard HSA with a fixed
coupling. Modifications generated by the η′-meson mass effects are discussed.
PACS 12.38.Bx; 14.40.Aq; 11.10.Hi 相似文献
9.
Analysis of edge-state energies in the integer quantum
Hall effect is carried out within the semiclassical approximation.
When the system is wide so that each edge can be considered
separately, this problem is equivalent to that of a one dimensional
harmonic oscillator centered at x = xc and an infinite wall at
x = 0, and appears in numerous physical contexts. The eigenvalues
En(xc) for a given quantum number n are solutions of the
equation S(E,xc)=π[n+ γ(E,xc)] where S is the WKB
action and 0 < γ < 1 encodes all the information on the
connection procedure at the turning points.
A careful implication of the WKB connection formulae results in an
excellent approximation to the exact energy eigenvalues. The
dependence of γ[En(xc),xc] ≡γn(xc)
on xc is analyzed between its two extreme values
as xc ↦-∞ far inside the sample
and as xc ↦∞ far outside the sample.
The edge-state energiesEn(xc) obey an almost exact scaling
law of the form
and the scaling function f(y) is explicitly elucidated. 相似文献
10.
I. K. Bensafa P. Achenbach M. Ases Antelo C. Ayerbe D. Baumann R. Böhm D. Bosnar E. Burtin X. Defaÿ N. D'Hose M. Ding M. O. Distler L. Doria H. Fonvieille J. M. Friedrich J. Friedrich J. García Llongo P. Janssens G. Jover Mañas M. Kohl G. Laveissière M. Lloyd M. Makek J. Marroncle H. Merkel P. Merle U. Müller L. Nungesser B. Pasquini R. Pérez Benito J. Pochodzalla M. Potokar G. Rosner S. Sánchez Majos M. Seimetz S. Širca T. Spitzenberg G. Tamas R. Van de Vyver L. Van Hoorebeke Th. Walcher M. Weis 《The European Physical Journal A - Hadrons and Nuclei》2007,32(1):69-75
The beam-helicity asymmetry has been measured simultaneously for the reactions
p→epγ and
p→epπ
0 in the Δ(1232)-resonance region at Q
2 = 0.35(GeV/c)2. The experiment was performed at MAMI with a longitudinally polarized beam and an out-of-plane detection of the proton. The
results are compared with calculations based on dispersion relations for virtual Compton scattering and with the MAID model
for pion electroproduction. There is an overall good agreement between experiment and theoretical calculations. The remaining
discrepancies may be ascribed to an imperfect parametrization of some γ
(*)
N→πN multipoles, mainly contributing to the non-resonant background. The beam-helicity asymmetry in both channels (γ and π
0) shows a good sensitivity to these multipoles and should allow future improvement in their parametrization. 相似文献
11.
After deriving the projected stress tensor in cylindrical geometry for a fluid membrane described by the Helfrich Hamiltonian,
we calculate the average force f exerted by a thermally fluctuating nanotubule of radius R , and its standard deviation
f . We obtain f and
f in terms of the internal membrane tension , the bending rigidity , the temperature k
B
T and a molecular cutoff . We find for f a shift ∼ 1/ with respect to the mean field behavior ∼ . We obtain (
f )2 ∼ R ln(R/b) where b is a molecular length,
f being typically small compared to f . Taking into account the difference between the internal tension and the actual mechanical tension applied to the membrane from which the tubule is drawn, we discuss the amplitude of the fluctuation-induced corrections to
the average force. Our results, obtained in the harmonic approximation, hold for tubules with aspect ratio not larger than
200 , of radius significantly smaller than 100nm, that are connected to a large membrane reservoir, e.g., a giant vesicle. 相似文献
12.
S. Procureur 《The European Physical Journal A - Hadrons and Nuclei》2007,32(4):483-487
The most recent determinations of the gluon polarization in the nucleon,
, obtained at RHIC and COMPASS experiments, are reviewed. The former accesses the gluon polarization mainly through the production
of neutral pions (PHENIX) or jets (STAR) in polarized proton collisions. The latter uses the photon-gluon fusion in polarized
lepton-nucleon scattering, tagged either by open charm or high-pT hadrons production. All the results are in good agreement, and favour values of ΔG roughly between 0 and 0.5 at a few (GeV/c)2 , thus in contradiction with what could be derived from the Ellis-Jaffe sum rule and the axial anomaly. Much stronger constraints
will be obtained in a near future by both programs, helping us to clarify the role of gluons in the nucleon spin. 相似文献
13.
I. D. Petrov V. L. Sukhorukov M. W. Ruf H. Hotop 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2009,53(3):289-302
Absolute photoionization cross sections for Ne atoms in the excited
levels (Paschen notation
) were calculated at near threshold energies within
the configuration interaction Pauli-Fock approach including core polarization.
The computed spectra and the lineshape parameters of the odd parity
2p1/2
5ns′/d′ autoionizing resonances are
found to be in good agreement with high resolution laser spectroscopic
results. Guided by the theoretical results, improved analyses of the measured
spectra by superimposed Fano-type profiles were achieved. Theoretical
predictions are presented for resonances which have not yet been studied
experimentally. In addition, we report the absolute partial photoionization
cross sections for the 2P3/2 and 2P1/2 channel at
photoelectron energies up to 7 eV. Except for the highest lying 2p1(1S0) level, these cross sections monotonically decrease with
energy (as reported earlier in single-electron calculations for the
Ne(2p53p) configuration) with branching ratios which essentially reflect
the core composition of the 2px levels. For the 2p1 level the resonance structure and the
partial cross sections are strongly influenced by a
Cooper-Seaton minimum in the d3/2
′ channel,located just above the 2P1/2 ionization limit. 相似文献
14.
D. Savran W. Bayer D. Galaviz S. Müller K. Sonnabend A. Zilges 《The European Physical Journal A - Hadrons and Nuclei》2008,36(1):17-20
High-resolution photon scattering experiments have been performed on the nucleus 45Sc at the Darmstadt superconducting electron accelerator S-DALINAC using bremsstrahlung beams with end point energies of 5.0
and 7.0MeV. Energies, absolute cross-sections and decay widths of 50 states, most of them previously unknown, have been determined.
The results are compared to (γ,
) experiments on the neighbouring closed proton shell isotope 44Ca . 相似文献
15.
R. K. Niven 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,70(1):49-63
We examine the combinatorial or probabilistic definition (“Boltzmann’s principle”) of the entropy or cross-entropy function
H ∝ or D ∝ - , where is the statistical weight and the probability of a given realization of a system. Extremisation of H or D, subject to any constraints, thus selects the
“most probable” (MaxProb) realization. If the system is multinomial, D converges asymptotically (for number of entities N
↦∞) to the Kullback-Leibler cross-entropy DKL; for equiprobable categories in a system, H converges to the Shannon entropy HSh. However, in many cases or is not multinomial and/or does not satisfy an asymptotic limit. Such systems cannot meaningfully be analysed with DKL or HSh, but can be analysed directly by MaxProb. This study reviews several examples, including (a) non-asymptotic systems; (b)
systems with indistinguishable entities (quantum statistics); (c) systems with indistinguishable categories; (d) systems represented
by urn models, such as “neither independent nor identically distributed” (ninid) sampling; and (e) systems representable in
graphical form, such as decision trees and networks. Boltzmann’s combinatorial definition of entropy is shown to be of greater
importance for “probabilistic inference” than the axiomatic definition used in information theory. 相似文献
16.
G. Meierhofer P. Kudejova L. Canella P. Grabmayr J. Jochum J. Jolie 《The European Physical Journal A - Hadrons and Nuclei》2009,40(1):61-64
The thermal neutron capture cross-sections of the 76Ge(n,)77Ge and the 76Ge(n,)77m
Ge reactions have been measured by activating targets of isotopically enriched GeO2 through cold neutrons. The -decay spectra after the -decay of 77Ge and 77m
Ge were measured with HPGe detectors. From these spectra the cross-sections for the 76Ge(n,) reactions were derived relative to the cross-section of 197Au using the absolute emission probabilities of the observed -ray energies. The methods used in this work result in smaller systematic uncertainties than those obtained in previous experiments. 相似文献
17.
18.
D. Elsner A. Süle P. Barneo P. Bartsch D. Baumann J. Bermuth R. Böhm D. Bosnar M. Ding M. Distler D. Drechsel I. Ewald J. Friedrich J. M. Friedrich S. Grözinger P. Jennewein S. Kamalov F. H. Klein M. Kohl K. W. Krygier H. Merkel P. Merle U. Müller R. Neuhausen Th. Pospischil M. Potokar G. Rosner H. Schmieden M. Seimetz O. Strähle L. Tiator Th. Walcher M. Weis 《The European Physical Journal A - Hadrons and Nuclei》2006,27(1):91-97
The reaction p(e, e'p)π0 has been studied at Q2 = 0.2 (GeV/c)2 in the region of W = 1232MeV. From measurements left and right of
, cross-section asymmetries ρLT have been obtained in forward kinematics ρLT(
= 20°) = (- 11.68±2.36stat±2.36sys) and backward kinematics ρLT(
= 160°) = (12.18±0.27stat±0.82sys) π0. Multipole ratios
{S1+ * M1+}/| M1+|2 and
{S0+ * M1+}/| M1+|2 were determined in the framework of the MAID2003 model. The results are in agreement with older data. The unusally strong
negative
{S0+ * M1+}/| M1+|2 required to bring also the result of Kalleicher et al. in accordance with the rest of the data is almost excluded. 相似文献
19.
A semi-phenomenological theory of variable-range hopping (VRH) is developed for two-dimensional (2D) quasi-one-dimensional
(quasi-1D) systems such as arrays of quantum wires in the Wigner crystal regime. The theory follows the phenomenology of Efros,
Mott and Shklovskii allied with microscopic arguments. We first derive the Coulomb gap in the single-particle density of states,
g(ε), where ε is the energy of the charge excitation. We then derive the main exponential dependence of the electron conductivity
in the linear (L), i.e. σ(T) ∼exp [-(TL/T)γL], and current in the non-linear (NL), i.e.
, response regimes (
is the applied electric field). Due to the strong anisotropy of the system and its peculiar dielectric properties we show
that unusual, with respect to known results, Coulomb gaps open followed by unusual VRH laws, i.e. with respect to the disorder-dependence
of TL and
and the values of γL and γNL. 相似文献
20.
A. Borschevsky E. Eliav M. J. Vilkas Y. Ishikawa U. Kaldor 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2007,45(1):115-119
Transition energies of the superheavy element lawrencium, including the ionization potential, excitation energies and electron
affinities, are calculated by the intermediate Hamiltonian coupled cluster method. A large basis set (37s31p26d21f16g11h6i)
is used, as well as an extensive P space (6s5p4d2f1g). The outer 43 electrons are correlated. Accuracy is monitored by applying
the same approach to lutetium, the lighter homologue of Lr, and comparing with experimentally known energies. QED corrections
are
included. The main goal is to predict excitation energies, in anticipation of planned spectroscopy of Lr.
The ground state of Lr is
, unlike the
of Lu. Predicted Lr excitations with large transition moments in the prime range for the planned experiment, 20 000–30 000 cm-1, are 7p→8s at 20 100 cm-1
and 7p→7d at 28 100 cm-1. The average absolute
error of 20 excitation energies of Lu is 423 cm -1, and the error limits for Lr are put at 700 cm-1.
The two electron affinities measured recently for Lu are reproduced within 55 cm-1, and a third bound state of Lu- is predicted. 相似文献