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1.
Current-voltage (J-V) and differential-conductivity-voltage ( dJ/dV-V) characteristics are analytically calculated at zero temperature for a point contact consisting of: two Peierls conductors
P
( = 1, 2) separated by an insulator (I). Here P is a conductor with charge density wave (CDW). The J-V and dJ/dV-V characteristics depend on the CDW phases ( = 1, 2) in the mean field approximation. To calculate them analytically we assumed, = ≡Δ where ( = 1, 2) are the energy gaps of P
( = 1, 2). The current J has a discontinuous jump at eV = 2Δ for ϕ
1 = ϕ
2≠ 0. The differential conductivity dJ/dV has a singularity at eV = 2Δ for ϕ
1 = ϕ
2≠ 0. The relation J(V,ϕ
1,ϕ
2) = - J(- V,ϕ
1 + π,ϕ
2 + π) is obtained.
Received 4 July 2001 and Received in final form 13 September 2001 相似文献
2.
On the basis of the experimental data on diffractive processes in πp, pp and pˉp collisions at intermediate, moderately high and high energies, we restore the scattering amplitude related to the t-channel exchange by vacuum quantum numbers by taking account of the diffractive s-channel rescatterings. At intermediate and moderately high energies, the t-channel exchange amplitude turns, with a good accuracy, into an effective pomeron which renders the results of the additive
quark model. At superhigh energies the scattering amplitude provides a Froissart-type behaviour, with an asymptotic universality
of cross sections such as σtot
πp/σtot
pp→ 1 at s→∞. The quark structure of hadrons being taken into account at the level of constituent quarks, the cross sections of pion
and proton (antiproton) in the impact parameter space of quarks, σπ(r
1⊥, r
2⊥; s) and σp(r
1⊥, r
2⊥, r
3⊥; s), are found as functions of s. These cross sections implicate the phenomenon of colour screening: they tend to zero at |r
i⊥−r
k⊥|→ 0. The effective colour screening radius for pion (proton) is found for different s. The predictions for the diffractive cross sections at superhigh energies are presented.
Received: 15 December 1998 相似文献
3.
Shuweia Xu Yuanxiang Xie Yong Yu Zhankui Li Qiangyan Pan Chunfang Wang Jianping Xing Tianmei Zhang 《The European Physical Journal A - Hadrons and Nuclei》2000,8(4):435-437
The available astrophysical S(E) factor data for the reaction 7Li (p,α)α at 10 < E < 1000keV exhibit an exponential increase at low energies due to the effects of electron screening. A parametrisation of
the data using a non-resonant, direct process and two subthreshold resonances reproduces the data at energies E≥ 100keV, while at lower energies this calculated S
b(E) factor curve for bare nuclides drops below the data, which in turn represent the case of electron-shielded nuclides, i.e. the electron-shielded S
s(E) factor. The comparison between S
b(E) and S
s(E) leads to an electron-screening potential energy U
e = 350eV, which is much higher than the adiabatic limit of 175eV and not understood at present. The deduced value of S
b(0) is considerably smaller than the previously adopted value of 59keV b, significantly increasing the calculated abundance
of 7Li in big-bang nucleosynthesis. The Trojan-horse method was applied to the reaction 7Li (p,α)α to determine the energy dependence of the S
b(E) factor for 10 < E < 370keV, free from the effects of the Coulomb barrier and electron screening. The THM results are close to the calculated
S
b(E) curve and suggest that the THM may become a powerful way to obtain improved information on low-energy cross-sections and
associated electron-screening effects in a model-independent way.
Received: 9 September 2000 / Accepted: 5 December 2000 相似文献
4.
M. Martínez J.-L. Pichard 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,30(1):93-100
The two dimensional crossover from independent particle towards collective motion is studied using 2 polarized electrons (spinless
fermions) interacting via a U/r Coulomb repulsion in a L×L square lattice with periodic boundary conditions and nearest neighbor hopping t. Three regimes characterize the ground state when U/t increases. Firstly, when the fluctuation Δr of the spacing r between the two particles is larger than the lattice spacing a, there is a scaling length L
0 = π2(t/U) such that the relative fluctuation Δr/〈r〉 is a universal function of the dimensionless ratio L/L
0, up to finite size corrections of order L-2. L < L
0 and L > L
0 are respectively the limits of the free particle Fermi motion and of the correlated motion of a Wigner molecule. Secondly,
when U/t exceeds a threshold U
*(L)/t, Δr becomes smaller than a, giving rise to a correlated lattice regime where the previous scaling breaks down and analytical expansions in powers of
t/U become valid. A weak random potential reduces the scaling length and favors the correlated motion.
Received 28 March 2002 Published online 19 November 2002 相似文献
5.
A ππ, ˉKK, and ρρ(ωω) fully coupled channel model is used to predict the lowest isospin S, P, D, F-wave phase shifts and inelasticities
for elastic ππ scattering from threshold to 2.0 GeV. As input the S-matrix is required to exhibit poles corresponding to the
meson resonance table of the Particle Data Group. As expected, the ππ inelasticity is very strongly related to the opening
of the ˉK channel near 1 GeV, and the opening of ρρ(4π) and ωω(6π) channels in the 1.5 GeV region. The predictions of this model are
compared to the various elastic ππ→ππ amplitudes, that were obtained from analyses of π− p →π−π+n data. The role of the various resonances, in particular the glueball candidate f
0(1500) and the f
J(1710) is investigated.
Received: 19 November 1997 相似文献
6.
W. Cassing Ye.S. Golubeva L.A. Kondratyuk 《The European Physical Journal A - Hadrons and Nuclei》2000,7(2):279-285
We study the possibility to measure the elastic ΦN (Φ≡J/ψ,ψ(2S), ψ(3770), χ2c) scattering cross section in the reaction ˉp+d→Φ+n
sp and the elastic D(ˉD)N scattering cross section in the reaction ˉp+d→D
−
D
0
p
sp. Our studies indicate that the elastic scattering cross sections can be determined for Φ momenta about 4–6 GeV/c and D/ˉD momenta 2–5 GeV/c by selecting events with p
t≥ 0.4 GeV/c for Φ's and p
t(p
sp) ≥ 0.5 GeV/c for D/ˉD-meson production.
Received: 8 November 1999 相似文献
7.
Lei Gao Yanyan Huang 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,33(2):165-171
The effective linear and nonlinear optical properties of metal/dielectric composite media, in which ellipsoidal metal inclusions
are distributed in shape, are investigated. The shape distribution function P(L
x, L
y) is assumed to be 2Δ-2θ(L
x - 1/3 + Δ/3)θ(L
y - 1/3 + Δ/3)θ(2/3 + Δ/3 - L
x - L
y), where θ( . . . ) is the Heaviside function, Δ is the shape variance and Li are the depolarization factors of the ellipsoidal inclusions along i-symmetric axes (i = x, y). Within the spectral representation, we adopt Maxwell-Garnett type approximation to study the effect of shape variance Δ
on the effective nonlinear optical properties. Numerical results show that both the effective linear optical absorption α
∼ ωIm() and the modulus of the effective third-order optical nonlinearity enhancement |χ(3)
e|/χ(3)
1 exhibit the nonmonotonic behavior with Δ. Moreover, with increasing Δ, the optical absorption and the nonlinearity enhancement
bands become broad, accompanied with the decrease of their peaks. The adjustment of Δ from 0 to 1 allows us to examine the
crossover behavior from no separation to large separation between optical absorption and nonlinearity enhancement peaks. As
Δ → 0, i.e., the ellipsoidal shape deviates slightly from the spherical one, the dependence of |χ(3)
e|/χ(3)
1 on Δ becomes strong first and then weak with increasing the imaginary part of inclusions' dielectric constant. In the dilute
limit, the exact formula for the effective optical nonlinearity is derived, and the present approximation characterizes the
exact results better than old mean field one does.
Received 10 December 2002 Published online 4 June 2003
RID="a"
ID="a"e-mail: lgaophys@pub.sz.jsinfo.net 相似文献
8.
L. Bartosch P. Kopietz 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,28(1):29-36
We consider the effect of Coulomb interactions on the average density of states (DOS) of disordered low-dimensional metals
for temperatures T and frequencies ω smaller than the inverse elastic life-time 1/τ. Using the fact that long-range Coulomb interactions in two dimensions (2d) generate ln2-singularities in the DOS ν(ω) but only ln-singularities in the conductivity σ(ω), we can re-sum the most singular contributions
to the average DOS via a simple gauge-transformation. If σ(ω) > 0, then a metallic Coulomb gapν(ω) ∝ |ω|/e
4 appears in the DOS at T = 0 for frequencies below a certain crossover frequency Ω
2 which depends on the value of the DC conductivity σ(0). Here, - e is the charge of the electron. Naively adopting the same procedure to calculate the DOS in quasi 1d metals, we find ν(ω) ∝ (|ω|/Ω
1)1/2exp(- Ω
1/|ω|) at T = 0, where Ω
1 is some interaction-dependent frequency scale. However, we argue that in quasi 1d the above gauge-transformation method is on less firm grounds than in 2d. We also discuss the behavior of the DOS at finite temperatures and give numerical results for the expected tunneling conductance
that can be compared with experiments.
Received 28 August 2001 / Received in final form 28 January 2002 Published online 9 July 2002 相似文献
9.
L. Gialanella D. Rogalla F. Strieder S. Theis G. Gyürki C. Agodi R. Alba M. Aliotta L. Campajola A. Del Zoppo A. D'Onofrio P. Figuera U. Greife G. Imbriani A. Ordine V. Roca C. Rolfs M. Romano C. Sabbarese P. Sapienza F. Schümann E. Somorjai F. Terrasi H.P. Trautvetter 《The European Physical Journal A - Hadrons and Nuclei》2001,11(3):357-370
An excitation function of the ground-state γ0-ray capture transition in 12C (α,γ)16O at θγ = 90° was obtained in far geometry using six Ge detectors, where the study of the reaction was initiated in inverse kinematics
involving a windowless gas target. The detectors observed predominantly the E1 capture amplitude. The data at E = 1.32 to 2.99 MeV lead to an extrapolated astrophysical S factor S
E1(E
0) = 90±15 keV b at E
0 = 0.3 MeV (for the case of constructive interference between the two lowest E1 sources), in good agreement with previous works. However, a novel Monte Carlo approach in the data extrapolation reveals
systematic differences between the various data sets such that a combined analysis of all available data sets could produce
a biased estimate of the S
E1(E
0) value. As a consequence, the case of destructive interference between the two lowest E1 sources with S
E1(E
0) = 8±3 keV b cannot be ruled out rigorously.
Received: 6 June 2001 / Accepted: 26 July 2001 相似文献
10.
M. Vatasescu F. Masnou-Seeuws 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2002,21(2):191-204
The paper contains a time-dependent investigation of the tunneling effect observed in the photoassociation spectrum of Cs2 and attributed to the 0g
-(6s, 6p
3/2) double well. When by photoassociation of two cold cesium atoms a vibrational level of the outer well is populated, tunneling
is an efficient mechanism for transferring the population to the inner well (R < 15a
0), where spontaneous emission may lead to formation of cold molecules in low vibrational levels of the a
3Σ+
u(6s, 6s) electronic state. This tunneling effect is analyzed by wavepackets propagation, first considering the double well potential
alone, and following a packet made by a superposition of states initially located at large distances. Characteristic times
for the vibration dynamics, corresponding to a beating phenomenon between the two wells, to partial “revival” at large distances,
and to maxima in the population localized in the inner well are reported and discussed. Second, we simulate the two-channels
a
3Σ+
u(6s, 6s)↦0g
-(6s, 6p
3/2) photoassociation at detunings around 2.9 cm-1: the inner well can be populated either by the excitation of a vibrational level of the external well (resonant excitation),
or by tuning the photoassociation laser at the energy of the inner well level which displays tunneling (“off-resonance excitation”).
In the first case the photoassociation is efficient, while the tunneling probability is small; in the second, the tunneling
probability is large, so that despite the poor efficiency of the photoassociation process, more population can be transferred
to the inner well. This second choice is shown to be very sensitive to the laser intensity, which could be used to control
the population of the inner well and hence the formation of ultracold molecules in low vibrational levels.
Received 19 April 2002 Published online 1st October 2002
RID="a"
ID="a"e-mail: francoise.masnou@lac.u-psud.fr 相似文献
11.
12.
J. Desbois 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,24(2):261-266
The spectral determinant of the Schr?dinger operator ( - Δ + V(x)) on a graph is computed for general boundary conditions. (Δ is the Laplacian and V(x) is some potential defined on the graph). Applications to restricted random walks on graphs are discussed.
Received 9 July 2001 相似文献
13.
M. Bender T. Cornelius G.A. Lalazissis J.A. Maruhn W. Nazarewicz P.-G. Reinhard 《The European Physical Journal A - Hadrons and Nuclei》2002,14(1):23-28
Recent mass measurements show a substantial weakening of the binding-energy difference δ2p(Z, N) = E(Z - 2, N) - 2E(Z, N) + E(Z + 2, N) in the neutron-deficient Pb isotopes. As δ2p is often attributed to the size of the proton magic gap, it might be speculated that reduction in δ2p is related to a weakening of the spherical Z = 82 shell. We demonstrate that the observed trend is described quantitatively by self-consistent mean-field models in terms
of deformed ground states of Hg and Po isotopes.
Received: 25 October 2001 / Accepted: 28 February 2002 相似文献
14.
J. Horbach W. Kob K. Binder 《The European Physical Journal B - Condensed Matter and Complex Systems》2001,19(4):531-543
We present the results of extensive molecular dynamics computer simulations in which the high frequency dynamics of silica,
i.e. for frequencies ν > 0.5 THz, is investigated in the viscous liquid state as well as in the glass state. We characterize the
properties of high frequency sound modes by analyzing J
l(q,ν) and J
t(q,ν), the longitudinal and transverse current correlation function, respectively. For wave-vectors q > 0.4 ?-1 the spectra are sitting on top of a flat background. The dynamic structure factor S(q,ν) exhibits for q > 0.23 ?-1 a boson peak which is located nearly independent of q around 1.7 THz and for which the intensity scales approximately linearly with temperature. We show that the low frequency
part of the boson peak is mainly due to the elastic scattering of transverse acoustic modes with frequencies around 1 THz.
The strength of this scattering depends on q and is largest around q = 1.7 ?-1, the location of the first sharp diffraction peak in the static structure factor. By studying S(q,ν) for different system sizes we show that strong finite size effects are present in the low frequency part of the boson
peak in that for small systems part of its intensity is missing. We discuss the consequences of these finite size effects
for the structural relaxation.
Received 27 June 2000 and Received in final form 9 January 2001 相似文献
15.
Z. Rudy W. Cassing L. Jarczyk B. Kamys P. Kulessa 《The European Physical Journal A - Hadrons and Nuclei》2002,15(3):303-314
The production of K+-mesons in proton-nucleus collisions from 1.0 to 2.5GeV is analyzed with respect to one-step nucleon-nucleon ( NN → NYK
+) and two-step Δ-nucleon ( ΔN → K
+
YN) or pion-nucleon ( πN → K
+
Y) production channels on the basis of a coupled-channel transport approach (CBUU) including the kaon final-state interactions.
The influence of momentum-dependent potentials for the nucleon, hyperon and kaon in the final state are studied as well as
the importance of K+ elastic rescattering in the target nucleus. The transport calculations are compared to the experimental K+ spectra taken at LBL Berkeley, SATURNE, CELSIUS, GSI and COSY-Jülich. It is found that the momentum-dependent baryon potentials
affect the excitation function of the K+ cross-section; at low bombarding energies of ∼ 1.0GeV the attractive baryon potentials in the final state lead to a relative
enhancement of the kaon yield, whereas the net repulsive potential at bombarding energies ∼ 2GeV causes a decrease of the
K+ cross-section. Furthermore, it is pointed out that especially the K+ spectra at low momenta (or kinetic energy T
K) allow to determine the in-medium K+ potential almost model independently due to a relative shift of the K+ spectra in kinetic energy that arises from the acceleration of the kaons when propagating out of the nuclear medium to free
space, i.e. converting the potential energy to the kinetic energy of the free kaon.
Received: 28 January 2002 / Accepted: 3 June 2002 / Published online: 19 November 2002
RID="a"
ID="a"e-mail: Wolfgang.Cassing@theo.physik.uni-giessen.de
Communicated by P. Schuck 相似文献
16.
Ricardo Becerril Tonatiuh Matos Luis Ureña-López 《General Relativity and Gravitation》2006,38(4):633-641
Oscillatons are spherically symmetric solutions to the Einstein–Klein–Gordon equations. These solutions are non-singular, asymptotically flat, and with periodic time dependency. In this paper, we investigate the geodesic motion of particles moving around of an oscillatonic field. Bound orbits are found for particular values of the particles' angular momentum L and their initial radial position r
0. It is found that the radial coordinate of such particles oscillates in time and we are able to predict the corresponding oscillating period as well as its amplitude. We carry out this study for the quadratic V(φ) = m
Φ Φ2/2 scalar field potential. We discuss possible ways to follow in order to connect this kind of studies with astrophysical observations. 相似文献
17.
G. Katomeris F. Selva J.-L. Pichard 《The European Physical Journal B - Condensed Matter and Complex Systems》2003,31(3):401-412
In 1969, Andreev and Lifshitz have conjectured the existence of a supersolid phase taking place at zero temperature between
the quantum liquid and the solid. In this and a succeeding paper, we re-visit this issue for a few polarized electrons (spinless
fermions) interacting via a U/r Coulomb repulsion on a two dimensional L×L square lattice with periodic boundary conditions and nearest neighbor hopping t. This paper is restricted to the magic number of particles N = 4 for which a square Wigner molecule is formed when U increases and to the size L = 6 suitable for exact numerical diagonalizations. When the Coulomb energy to kinetic energy ratio r
s = UL/(2t
) reaches a value r
s
F ≈ 10, there is a level crossing between ground states of different momenta. Above r
s
F, the mesoscopic crystallization proceeds through an intermediate regime ( r
s
F < r
s < r
s
W ≈ 28) where unpaired fermions with a reduced Fermi energy co-exist with a strongly paired, nearly solid assembly. We suggest
that this is the mesoscopic trace of the supersolid proposed by Andreev and Lifshitz. When a random substrate is included,
the level crossing at r
s
F is avoided and gives rise to a lower threshold r
s
F(W) < r
s
F where two usual approximations break down: the Wigner surmise for the distribution of the first energy excitation and the
Hartree-Fock approximation for the ground state.
Received 21 June 2002 Published online 14 February 2003
RID="a"
ID="a"e-mail: jpichard@cea.fr 相似文献
18.
R. Krücken S.J. Asztalos R.M. Clark M.A. Deleplanque R.M. Diamond P. Fallon I.Y. Lee A.O. Macchiavelli G.J. Schmid F.S. Stephens K. Vetter Jing-Ye Zhang 《The European Physical Journal A - Hadrons and Nuclei》2001,10(2):151-155
High-spin states in 112Pd were studied using prompt γ-ray spectroscopy with Gammasphere following heavy-ion-induced fission in the reaction 18O + 208Pb at 91 MeV. A new 8+ level at 2638 keV was discovered with transitions connecting it to the yrast band and the quasi-gamma band. The three, now
established, closely spaced 8+ states indicate a mixing between the ground-state band, s-band, and quasi-gamma band. Several high-spin structures with likely negative parity have been extended to higher spin and
it is proposed that they are based on the νh
11/2(g
7/2
d
5/2) and νh
11/2(s
1/2
d
3/2) configurations.
Received: 28 November 2000 / Accepted: 8 February 2001 相似文献
19.
Verneuil E Clain J Buguin A Brochard-Wyart F 《The European physical journal. E, Soft matter》2003,10(4):345-353
A soft bead (radius R
b) is pressed with a force F against a hydrophobic glass plate through a water drop (“wet” JKR set-up). We observe with a fast camera the growth of the
contact zone bridging the rubber bead to the glass. Depending on the approach velocity V, two regimes are observed : i) at large V a liquid film is squeezed at the interface and dewets by nucleation and growth of a dry contact; ii) at low velocities, the
bead remains nearly spherical. As it comes into contact, the rubber bead spreads on the glass with a characteristic time (in
the range of one millisecond) τ ≈ ηR
b
2/F, where η is the liquid viscosity. The laws of spreading are interpreted by a balance of global mechanical and viscous forces.
Received: 22 December 2002 / Accepted: 24 March 2003 / Published online: 29 April 2003
RID="a"
ID="a"e-mail: brochard@curie.fr 相似文献
20.
M. Takigawa M. Ichioka K. Machida 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,27(3):303-311
Thermal conductivity κ
xx(T) under a field is investigated in d
x2 - y2-wave superconductors and isotropic s-wave superconductors by the linear response theory, using a microscopic wave function of the vortex lattice states. To study
the origin of the different field dependence of κxx(T) between higher and lower temperature regions, we analyze the spatially-resolved thermal conductivity around a vortex at
each temperature, which is related to the spectrum of the local density of states. We also discuss the electric conductivity
in the same formulation for a comparison.
Received 8 December 2001 and Received in final form 20 March 2002 Published online 6 June 2002 相似文献