共查询到20条相似文献,搜索用时 31 毫秒
1.
Miron Ya. Amusia Arkadiy S. Baltenkov Larissa V. Chernysheva 《Central European Journal of Physics》2008,6(1):14-25
We demonstrate rather interesting manifestations of co-existence of resonance features in characteristics of the photoionization
of 3d-electrons in Xe, Cs and Ba endohedral atoms. It is shown that for all of the considered atoms the reflection by the fullerene
shell of photoelectrons produced by the 3d subshell photoionization affects greatly partial photoionization cross-sections of 3d
5/2 and 3d
3/2 levels and respective angular anisotropy parameters, both dipole and non-dipole adding to all of them additional maximums
and minimums. The results obtained demonstrate distinctive differences between the three atoms. The calculations are performed
treating the 3/2 and 5/2 electrons as electrons of different kinds with their spins “up” and “down”. The effect of the C60 shell is accounted for in the frame of the “orange” skin potential model. It is essential that in the considered photon frequency
region the presented resonance features are not affected by the C60polarization.
相似文献
2.
G. A. Kozlov 《Physics of Particles and Nuclei》2010,41(6):954-956
A field model for a quark and an antiquark binding is described. Quarks interact via a gauge unparticle (“ungluon”). The model
is formulated in terms of Lagrangian which features the source field S(x) which becomes a local pseudo-Goldstone field of conformal symmetry — the pseudodilaton mode and from which the gauge non-primary
unparticle field is derived by B
μ(x) ∼ ∂μ
S(x). Because the conformal sector is strongly coupled, the mode S(x) may be one of new states accessible at high energies. We have carried out an analysis of the important quantity that enters
in the “ungluon” exchange pattern — the “ungluon” propagator. 相似文献
3.
Over the last ten years interest in the physics of de Sitter space—time has been growing very fast. Besides the supposed existence
of a “de Sitterian period” in inflation theories, the observational evidence of an acceleration of the universe expansion
(interpreted as a positive cosmological constant or a “dark energy” or some form of “quintessence”) has triggered a lot of
attention in the physics community. A specific de Sitterian field called “massless minimally coupled field” (mmc) plays a
fundamental role in inflation models and in the construction of the de Sitterian gravitational field. A covariant quantization
of the mmc field, à la Krein—Gupta—Bleuler was proposed in Class. Quantum. Grav. 17, 1415 (2000). In this talk, we will review this construction and explain the relevance of such a field in the construction
of a massless spin-2 field in de Sitter space—time. 相似文献
4.
Relativistic constraint mechanics yields consistent systems of coupled Dirac equations for pairs of spinning particles. We
explicitly connect these equations to the Bethe-Salpeter equation of quantum field theory and to the interactions of classical
Fokker-Tetrode dynamics (and hence to classical relativistic field theory) to obtain versions of these equations governed
by systems of (possibly noncoulombic) relativistic potentials whose detailed structures contain important relativistic effects
like correct Darwin interactions. We recast the defining pair of Dirac equations in a number of equivalent but important forms—“external
potential,” Sazdjian, hyperbolic, and Breit— and examine their interconnection. Since the potentials in these equations are
no more singular than — 1/4r2 we are able to solve appropriate versions of them nonperturbatively for the qˉq system to obtain a very good fit to the entire
meson spectrum and for the e
+
e
−
system to calculate the positronium spectrum of QED correct through order α
4
. 相似文献
5.
Using the neutron scattering lengths b determined experimentally for a majority of isotopes in last decades, one can in principic extract systematic information
on some nuclear properties of elements. A significant “scatter” of experimental values of the (related to b) nuclear radius R around the “classical” dependence R = r
0
A
1/3, where A is the mass number, is intriguing and requires a special attention. In this work, on extending the use of known formulas
of the theory of neutron scattering on nucleus represented by a rectangular radial symmetry potential well (or barrier), we
have determined the depths V
0 of the potential well and for many isotopes the position of the bound-state energy level E
b
in the well. The “scatter” mentioned above can be in part attributed to the four types of the s-type wave functions of slow
neutron interacting with nucleus, which appear in this model. In several cases the bound-state energy level is close to the
Fermi E
F
level of the free-nucleon model of nuclear matter of the constant density, independent of A. 相似文献
6.
Fabio Gavarini 《Czechoslovak Journal of Physics》2001,51(12):1330-1335
The “quantum duality principle” states that a quantisation of a Lie bialgebra provides also a quantisation of the dual formal
Poisson group and, conversely, a quantisation of a formal Poisson group yields a quantisation of the dual Lie bialgebra as
well. We extend this to a much more general result: namely, for any principal ideal domainR and for each primepεR we establish an “inner” Galois’ correspondence on the categoryHA of torsionless Hopf algebras overR, using two functors (fromHA to itself) such that the image of the first and the second is the full subcategory of those Hopf algebras which are commutative
and cocommutative, modulop, respectively (i.e., they are“quantum function algebras” (=QFA) and“quantum universal enveloping algebras” (=QUEA), atp, respectively). In particular we provide a machine to get two quantum groups — a QFA and a QUEA — out of any Hopf algebraH over a fieldk: apply the functors tok[ν] ⊗k H forp=ν.
A relevant example occurring in quantum electro-dynamics is studied in some detail.
Presented at the 10th International Colloquium on Quantum Groups: “Quantum Groups and Integrable Systems”, Prague, 21–23 June
2001 相似文献
7.
An algorithm has been proposed to build an estimate of the half-life of a “daughter” nucleus in case, when it is unknown,
which nucleus is its “mother” (“indefinite start time”). For a decay of the “mother” at an instant t we can determine P—a probability of such a decay, if we assume that each “mother”, which has been decayed before t has equal chances to be “mother” of this “daughter”:
$
\sum\limits_{i = 1}^{n_t } {exp\left( { - \frac{{t - t_i }}
{\tau }} \right)} ,
$
\sum\limits_{i = 1}^{n_t } {exp\left( { - \frac{{t - t_i }}
{\tau }} \right)} ,
相似文献
8.
M. Combescot O. Betbeder-Matibet 《The European Physical Journal B - Condensed Matter and Complex Systems》2007,55(1):63-76
The purpose of this paper is to show how the diagrammatic expansion
in fermion exchanges of scalar products of N-composite-boson
(“coboson”) states can be obtained in a practical way. The hard
algebra on which this expansion is based, will be given in an independent publication.
Due to the composite nature of the particles, the scalar products
of N-coboson states do not reduce to a set of Kronecker symbols, as
for elementary bosons, but contain subtle exchange terms between two or
more cobosons. These terms originate from Pauli exclusion between the
fermionic components of the particles. While our many-body
theory for composite bosons leads to write these scalar products as
complicated sums of products of “Pauli scatterings” between
two cobosons, they in fact correspond to fermion exchanges
between any number P of quantum particles, with
2 ≤P≤N. These P-body exchanges are nicely represented by the
so-called “Shiva diagrams”, which are topologically different from
Feynman diagrams, due to the intrinsic many-body nature of the Pauli
exclusion from which they originate. These Shiva diagrams in fact
constitute the novel part of our composite-exciton many-body theory
which was up to now missing to get its full
diagrammatic representation. Using them, we can now “see” through
diagrams the physics of any quantity in which enters N interacting
excitons — or more generally N composite bosons —, with fermion
exchanges included in an
exact — and transparent — way. 相似文献
9.
10.
It is shown that the temperature dependence of the liquid volume is well described by the equation $
V = A + BT + CT^2 + V_e \exp ( - E/RT),
$
V = A + BT + CT^2 + V_e \exp ( - E/RT),
where A, B, C, V
e
, and E are constants. This equation reflects two processes owing to which the liquid volume increases with temperature, namely,
anharmonic oscillations of molecules and formation of “holes.” 相似文献
11.
R. Thissen P. Lablanquie R.I. Hall M. Ukai K. Ito 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1998,4(3):335-342
Photoionization of rare gas clusters in the innervalence shell region has been investigated using threshold photoelectron
and photoion spectrometers and synchrotron radiation. Two classes of states are found to play an important role: (A) valence
states, correlated to dissociation limits involving an ion with a hole in its innervalence ns shell, (B) Rydberg states correlated to dissociation limits involving an ion with a hole in its outervalence np shell plus an excited neutral atom. In dimers, class A states are “bright”, that is, accessible by photoionization, and serve
as an entrance step to form the class B “dark” states; this character fades as the size of the cluster increases. In the dimer,
the “Mulliken” valence state is found to present a shallow potential well housing a few vibrational levels; it is predissociated by the
class B Rydberg states. During the predissociation a remarkable energy transfer process is observed from the excited ion that
loses its innershell electron to its neutral partner.
Received: 10 February 1998 / Revised: 17 July 1998 / Accepted: 31 July 1998 相似文献
12.
If string theory is correct, then our observable Universe may be a 3-dimensional “brane” embedded in a higher-dimensional
spacetime. This theoretical scenario should be tested via the state-of-the-art in gravitational experiments—the current and
upcoming gravity-wave detectors. Indeed, the existence of extra dimensions leads to oscillations that leave a spectroscopic
signature in the gravity-wave signal from black holes. The detectors that have been designed to confirm Einstein's prediction
of gravity waves, can in principle also provide tests and constraints on string theory.
Fourth Award in the 2005 Essay Competition of the Gravity Research Foundation. - Ed. 相似文献
13.
H. L. Kwok 《Applied physics. B, Lasers and optics》2009,94(2):279-282
Organic field-effect transistors (OFETs) have received significant attention recently because of the potential application
in low-cost flexible electronics. The physics behind their operation are relatively complex and require careful consideration
particularly with respect to the effect of charge trapping at the insulator–semiconductor interface and field effect in a
region with a thickness of a few molecular layers. Recent studies have shown that the so-called “onset” voltage (V
onset) in the rubrene OFET can vary significantly depending on past illumination and bias history. It is therefore important to
define the role of the interface trap states in more concrete terms and show how they may affect device performance. In this
work, we propose an equivalent-circuit model for the OFET to include mechanism(s) linked to trapping. This includes the existence
of a light-sensitive “resistor” controlling charge flow into/out of the interface trap states. Based on the proposed equivalent-circuit
model, an analytical expression of V
onset is derived showing how it can depend on gate bias and illumination. Using data from the literature, we analyzed the I–V characteristics of a rubrene OFET after pulsed illumination and a tetracene OFET during steady-state illumination. 相似文献
14.
Anastasios Mallios 《International Journal of Theoretical Physics》2006,45(8):1552-1588
“Geometry,” in the sense of the classical differential geometry of smooth manifolds (CDG), is put under scrutiny from the point of view of Abstract Differential Geometry (ADG). We explore potential physical implications of viewing things under the light of ADG, especially matters concerning the “gauge theories” of modern physics, when the latter are viewed (as they are actually regarded currently) as “physical theories of a geometrical character.” Thence, “physical geometry,” in connection with physical laws and the associated with them, within the background spacetime manifoldless context of ADG, “differential” equations, are also being discussed. 相似文献
15.
In this paper, one-dimensional (1D) nonlinear wave equations
16.
L. P. Ol’khovik Z. I. Sizova E. V. Shurinova A. S. Kamzin 《Physics of the Solid State》2010,52(2):311-316
This paper reports on a study of the field and temperature dependences of the parameters of the particle magnetic interaction
in a densely packed system of nanocrystals of the highly anisotropic hexagonal ferrite BaFe12O19 with the particles distributed in diameter within the range 10—100 nm and having volumes satisfying the criterion of “small
Stoner—Wohlfarth particles.” It is shown that the resultant particle interaction in the temperature range 300 K≤T≤640 K has a negative sign, whereas for T>640 K, it is positive. The maximum values of the parameter Δm allow classification of the interaction as moderate in strength. The temperature dependences of the interaction parameters
are found to correlate with manifestation of the size and surface effects in the system, which are characteristic of small
particles (transition to the superparamagnetic state, “surface” anisotropy, and reduced exchange interaction in a structurally
defective near-surface layer of particles). 相似文献
17.
Yu. A. Simonov 《Physics of Atomic Nuclei》2007,70(1):44-52
The 3d gluodynamics which governs the large-T quark—gluon plasma is studied in the framework of the field correlator method. Field correlators and spacial string tension
are derived through the gluelump Green’s functions. The glueball spectrum is calculated both in C = −1 as well as in C = +1 sectors, and multigluon bound states in the form of “gluon rings” and “gluon stars” are computed explicitly. Good overall
agreement with available lattice data is observed.
The text was submitted by the author in English. 相似文献
18.
The lattice vibration spectrum, rf permittivity, and dynamic Born charges have been calculated for ordered Pb2
B′B″O3 (B′=Ga, In, Lu; B″=Nb, Ta) solid solutions in terms of the generalized Gordon—Kim model. It has been shown that all compounds exhibit a ferroelectric
instability and that the frequencies of “soft” ferroelectric modes are close in magnitude. The ferroelectric phase-transition
temperatures and the spontaneous polarization in the ferroelectric phase of the solid solutions under consideration have been
calculated by the Monte Carlo method using the model Hamiltonian in the local mode approximation. The transition temperature
is found to increase with increasing atomic number of the B′ ion. 相似文献
19.
An apparatus is developed for investigating the dynamic deformation properties of cryoinsulation coatings in the temperature
range 8–293 K. One type of cryo-insulation material — polyurethane foam — is chosen as the object of investigation. Test measurements
on a polyurethane foam “pack” (metal substrate with a polyurethane foam coating) are performed at 0.01 Hz in the temperature
range 8–293 K. A jump in the temperature dependence of the dynamic shear modulus (by two orders of magnitude) is observed
in the temperature range 54–63 K. This feature is attributed to the solidification of the air present in the pores of the
polyurethane foam. Such a transition results in cementation of the polyurethane skeleton of the coating by the nitrogen and
oxygen “ice” that is formed.
Zh. Tekh. Fiz. 69, 116–118 (February 1999) 相似文献
20.
Vilson Tonin-Zanchin Erasmo Recami José A. Roversi Luis A. Brasca-Annes 《Foundations of Physics Letters》1994,7(2):167-179
Within a purely classical formulation of “strong gravity,” we associated hadron constituents (and even hadrons themselves)
with suitable stationary, axisymmetric solutions of certain new Einsteintype equations supposed to describe the strong field
inside hadrons. Such equations are nothing but Einstein equations—with cosmological term—suitably scaled down. As a consequence,
the cosmological constant Λ and the massesM result in our theory to be scaled up, and transformed into a “hadronic constant” and into “strong masses,” respectively.
Due to the unusual range of Λ andM values considered, we met a series of solutions of the Kerr-Newman-de Sitter (KNdS) type with rather interesting properties:
aim of the present work is putting forth such results, while “translating” them into the more popular language of ordinary
gravity.
The requirement that those solutions be stable, i.e., that their temperature (or surface gravity) bevanishingly small, implies the coincidence of at least two of their (in general, three) horizons. Imposing the stability condition of a certain
horizon does yield (once chosen the values ofJ, q and Λ) mass and radius of the associated black hole.
In the case of ordinary Einstein equations and for stable blackholes of the KNdS type, we get in particular Regge-like relations
among massM, angular momentumJ, chargeq and cosmological constant Λ; which did not receive enough attention in the previous literature. For instance, with the standard
definitionsQ
2 = Gq2/(4πε
0
c
4), a ≡ J/(Mc), m ≡GM/c
2, in the case Λ=0 in whichm
2=a2+Q2 and ifq is negligible, we findm
2=J. When considering, for simplicity, Λ>0 andJ=0 (andq still negligible), then we obtainm
2 = 1/(9Λ). In the most general case, the condition, for instance, of “triple coincidence” among the three horizons yields
for |Λa
2|<< 1 the couple of independent relationsm
2 = 2/(9Λ) andm
2 = 8(a
2 + Q2.
Another interesting point is that—with few exceptions—all such relations (amongM, J, q, Λ) lead to solutions that can be regarded as (stable) cosmological models.
Work partially supported by INFN, MURST, and CNR and by CNPq, FAPESP, and CAPES. 相似文献
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