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1.
We study spectral properties of
the discrete Laplacian H on the half-space
with random boundary condition ;
the V(n) are independent random variables on a
probability
space and λ is the coupling constant.
It is known that if the
V(n) have densities, then on the interval
[-2(d+1), 2(d+1)] (=σ(H
0),
the spectrum of the
Dirichlet Laplacian) the spectrum of H is P-a.s.
absolutely continuous for all λ [JL1].
Here we show that if the random potential P
satisfies the
assumption of Aizenman–Molchanov [AM], then there
are constants λ
d
and
Λ
d
such that for
|λ|<lambda;
d
and |λ|>
Λ
d
the spectrum of
H outside σ(H
0)
is P-a.s. pure point with exponentially decaying
eigenfunctions.
Received: 3 December 1998 / Accepted: 27 May 1999 相似文献
2.
B.M. Abramov S.A. Bulychjov A.I. Khanov Y.S. Krestnikov A.P. Krutenkova V.V. Kulikov M.A. Matsyuk I.A. Radkevich A.I. Sutormin E.N. Turdakina 《The European Physical Journal A - Hadrons and Nuclei》1998,1(2):115-116
We report on our measurement of the inclusive spectrum of positive pions from the reaction pp→π++X on a CH
2 internal target of the ITEP proton synchrotron at 1.5 GeV/c with a missing mass resolution of about 1 MeV/c2. The goal of our experiment was the search for the hypothetical narrow πNN resonance (0.5\ MeV/c2 width and a mass of 2.06\ GeV/c2) with I(J
P
P)=even(0−), called d′. We do not see any statistically significant d′-signal. The upper limit for d′ production cross-section in pp-interactions is near 2μb at 84%C.L.
Received: 5 November 1997 相似文献
3.
The renormalization of the solution of the Navier-Stokes equation for randomly stirred fluid with long-range correlations
of the driving force is analysed near two dimensions. It is shown that a local term must be added to the correlation function
of the random force for the correct renormalization of the model at two dimensions. The interplay of the short-range and long-range
terms in the large-scale behaviour of the model is analysed near two dimensions by the field-theoretic renormalization group.
A regular expansion in 2ε=d-2 and δ=2-λ is constructed, whered is the space dimension and λ the exponent of the powerlike correlation function of the driving force. It is shown that in
spite of the additional divergences, the asymptotic behaviour of the model near two dimensions is the same as in higher dimensions,
contrary to recent conjectures based on an incorrect renormalization procedure. 相似文献
4.
Sayan K. Chakrabarti 《General Relativity and Gravitation》2007,39(5):567-582
We obtain the quasinormal modes for tensor perturbations of Gauss–Bonnet (GB) black holes in d = 5, 7, 8 dimensions and vector perturbations in d = 5, 6, 7 and 8 dimensions using third order WKB formalism. The tensor perturbation for black holes in d = 6 is not considered because of the fact that the black hole is unstable to tensor mode perturbations. In the case of uncharged
GB black hole, for both tensor and vector perturbations, the real part of the QN frequency increases as the Gauss–Bonnet coupling
(α′) increases. The imaginary part first decreases upto a certain value of α′ and then increases with α′ for both tensor and vector perturbations. For larger values of α′, the QN frequencies for vector perturbation differs slightly from the QN frequencies for tensorial one. It has also been
shown that as α′ → 0, the quasinormal frequencies for tensor and vector perturbations of the Schwarzschild black hole can be obtained. We
have also calculated the quasinormal spectrum of the charged GB black hole for tensor perturbations. Here we have found that
the real oscillation frequency increases, while the imaginary part of the frequency falls with the increase of the charge.
We also show that the quasinormal frequencies for scalar field perturbations and the tensor gravitational perturbations do
not match as was claimed in the literature. The difference in the result increases if we increase the GB coupling. 相似文献
5.
Noam Berger 《Communications in Mathematical Physics》2002,226(3):531-558
We study the behavior of the random walk on the infinite cluster of independent long-range percolation in dimensions d= 1,2, where x and y are connected with probability . We show that if d<s<2d, then the walk is transient, and if s≥ 2d, then the walk is recurrent. The proof of transience is based on a renormalization argument. As a corollary of this renormalization
argument, we get that for every dimension d≥ 1, if d>s>2d, then there is no infinite cluster at criticality. This result is extended to the free random cluster model. A second corollary
is that when d≥& 2 and d>s>2d we can erase all long enough bonds and still have an infinite cluster. The proof of recurrence in two dimensions is based
on general stability
results for recurrence in random electrical networks. In particular, we show that i.i.d. conductances on a recurrent graph
of bounded degree yield a recurrent electrical network.
Received: 27 October 2000 / Accepted: 29 November 2001 相似文献
6.
Y. Zhang C. Y. Chen M. Huang Y. S. Wang Y. M. Zou 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2010,56(2):157-166
Ab initio calculations of the total dielectronic
recombination (DR) rate coefficients for thirteen ions along the NiI
isoelectronic sequence in the ground state (Kr8+, Mo14+,
Ag19+, Sn22+, Xe26+, Nd32+, Gd36+,
Yb42+, W46+, Au51+, Pb54+, At57+, and
U64+) have been performed using the flexible atomic code. The
level-by-level calculations are performed for evaluating the DR
contributions through the relevant Cu-like autoionizing inner-shell
excited 3l174l′n′′l′′ and 3l175l′n′′l′′ configuration complexes with n′′
≤15, which are associated with Δn=1 and Δn=2
core-excitations, respectively. The usual (n′′)-3 scaling
law is found to be invalid for low-Z ions. A level-by-level
extrapolation procedure is employed to obtain the contributions
through higher n′′ complexes. The decays to autoionizing
levels followed possibly by radiative cascades could enlarge the
rates at relatively high temperature by a factor up to about 23%.
For the whole isoelectronic ions the contributions from
3s23p63d9 4l′n′′l′′ dominate the total DR
rates while the contributions from the 3s23p63d9 5l′n′′l′′ configuration complexes are about 10-20% at
relatively high temperature. On the basis of the calculated results,
a general analytic formula for the total DR rate coefficients of all
the ions with 36≤Z ≤92 along the NiI isoelectronic
sequence is constructed. The comparisons of the rates obtained from
the general formula with those from the detailed calculations show
that the formula is of high precision, generally better than 3%
accuracy for electron temperatures kT≥0.1EI, where EI is
the ionization energy of the Cu-like ion. The present DR rates at
temperature above 1.0EI are larger than the previously published
data by a factor above 30%. The commonly used semiempirical formula
proposed by Burgess and modified by Merts may overestimate the rates
at high temperature by a factor of about 2 for low-Z ions. 相似文献
7.
Andre Toom 《Journal of statistical physics》1997,88(1-2):347-364
We consider space- and time-uniformd-dimensional random processes with linear local interaction, which we call harnesses and which may be used as discrete mathematical
models of random interfaces. Their components are rea random variablesa
s
t
, wheres ∈ Z
d
andt=0, 1, 2.,... At every time step two events occur: first, every component turns into a linear combination of itsN neighbors, and second, a symmetric random i.i.d. “noise”v is added to every component. For any σ ∈Z
d
+
define Δσ
a′
s
as follows. If σ=(0,...,0), σ=(0,...,0), Δσ
a
s
t
=a
s
t
. Then by induction,
wheree
i is thed-dimensional vector, whoseith component is one and other components are zeros. Denote |σ| the sum of components of σ. Call a real random variable ϕ symmetric
if it is distributed as −ϕ. For any symmetric random variable ϕpower decay or P-decay is defined as the supremum of thoser for which therth absolute moment of ϕ is finite. Convergence a.s., in probability and in law whent→∞ is examined in terms of P-decay(v): Ifd=1, σ=0 ord=2, σ=(0,0), Δσ
a
s
t
diverges. In all the other cases: If P-decay(v)<(d+2)/(d+|σ|), Δσ
a
s
t
diverges; if P-decay(v)>(d+2)/(d+|σ|), Δσ
a
s
t
, converges and P-decay(ν) For any symmetric random variable ϕexponential decay or E-decay is defined as the supremum of thoser for which the expectation of exp(|x|r) is finite. Let E-decay(v)>0. Whenever Δσ
a
s
t
converges (that is, ifd>2 or |σ|>0: Ifd>2, E-decay(lima
s
t
)=min(E-decay(v),d+2/2); if |σ|=1, E-decay (lim Δσ
a
s
t
)=min(E-decay(ν),d+2); if |σ| ⩾, E-decay (lim Δσ
a
s
t
)=E-decay(ν). 相似文献
8.
V. G. Nazin M. N. Mikheeva L. L. Lev V. A. Rogalev S. L. Molodtsov M. M. Brzhezinskaya 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2010,4(6):935-940
Photoelectron spectra and optical absorption spectra for clean surfaces of quasicrystalline samples of the Ti—Zr—Ni system
are measured. The resonant photoelectron spectra are also measured in the range of photon energies corresponding to Ni 2p and Zr 3d absorption thresholds. The change in the intensities of the spectrum of the valence band near the Zr 3d threshold is insignificant. The emission of Auger electrons increases near the Ni 2p threshold in a resonance way. Our studies make it possible to reveal certain specific features of the electronic structure
of quasicrystals, which can be used to construct models of actual electronic structures of quasi-crystalline materials. 相似文献
9.
Stellmack MA Viemeister NF Byrne AJ 《The Journal of the Acoustical Society of America》2005,118(1):346-352
Psychometric functions were measured for the discrimination of the interaural phase difference (IPD) of the envelope of a sinusoidally amplitude-modulated (SAM) 4-kHz pure tone for modulation frequencies of 128 and 300 Hz and modulation depths (m) of 0.2, 0.6, 0.9, and 1.0. Contrary to recent modeling assumptions, it was found that a constant change in normalized interaural envelope correlation, with or without additional model stages to simulate peripheral auditory processing, did not produce a constant level of performance. Rather, in some cases, performance could range from chance to near perfect across modulation depths for a given change in normalized interaural envelope correlation. This was also true for the maximum change in normalized interaural envelope correlation computed across the cross-correlation functions for the stimuli to be discriminated. The change in the interaural time difference (ITD) computed from the IPD accounted for discriminability across modulation depths better than the change in normalized interaural envelope correlation, although ITD could not account for all the data, particularly those for lower values of m. 相似文献
10.
Brungart DS 《The Journal of the Acoustical Society of America》1999,106(6):3589-3602
A series of experiments has examined the auditory localization of a nearby (< 1 m) sound source under four conditions: (1) a fixed-amplitude condition where loudness-based distance cues were available; (2) a monaural condition where the contralateral ear was occluded by an ear-plug and muff; (3) a high-pass condition where the stimulus bandwidth was 3 Hz to 15 kHz; and (4) a low-pass condition where the stimulus bandwidth was 200 Hz to 3 kHz. The results of these experiments were compared to those of a previous experiment that measured localization performance for a nearby broadband, random-amplitude source [Brungart et al., J. Acoust. Soc. Am. 106, 1956-1968 (1999)]. Directional localization performance in each condition was consistent with the results of previous far-field localization experiments. Distance localization accuracy improved slightly in the fixed-amplitude condition relative to the earlier broadband random-amplitude experiment, especially near the median plane, but was severely degraded in the monaural condition. Distance accuracy was also found to be highly dependent on the low-frequency energy of the stimulus: in the low-pass condition, distance accuracy was similar to that in the broadband condition, while in the high-pass condition, distance accuracy was significantly reduced. The results suggest that low-frequency interaural level differences are the dominant auditory distance cue in the proximal region. 相似文献
11.
Molecular oxygen detection in low pressure flames using cavity ring-down spectroscopy 总被引:1,自引:0,他引:1
Cavity ring down spectroscopy is used for measurement of the concentration profiles of oxygen in the low pressure (30 Torr) methane/nitrogen/oxygen flames. Three different equivalence ratios are used: 0.8, 1.0 and 1.17. Molecular oxygen concentration is monitored via rotational spectrum of b1
Σ
g
+←X3
Σ
g
- (v′=0-v′′=0) transition, also known as atmospheric A band, located near 750 nm. The P(15)P(15) line is used for concentration measurements. The sensitivity reached is 2.2×10-8 cm-1. The concentration profiles are in a good agreement with the ones calculated using GRI-3.0 mechanism. PACS 33.20.Kf; 33.70.Fd; 42.60.Da 相似文献
12.
Culling JF 《The Journal of the Acoustical Society of America》2007,122(5):2803-2813
Three experiments investigated the roles of interaural correlation (rho) and of the monaural power spectrum in the detection and discrimination of narrow-band-noise signals (462-539 Hz) in broadband maskers (0-3 kHz). The power and rho of the target band were independently controlled, while the flanking noise was fixed and diotic. Experiments 1 and 2 involved rho and power values that would be produced by specific values of signal-to-noise ratio (SNR) in the NoSpi binaural configuration. Listeners were required to discriminate different SNRs via a 2I-FC loudness-discrimination task. At low reference SNRs, changes in rho fully accounted for listeners' performance, but as reference SNR increased, additional energy in the target band played an increasing role. Experiment 2 showed that at these higher SNRs the combination of information from the power spectrum and rho was superadditive and could not be explained by simple signal-detection models. The equalization-cancellation (EC) theory would explain these data using the output from interaural cancellation, Y, rather than rho. Experiment 3 attempted to foil binaural processing, by fixing either rho or Y across intervals. Consistent with EC theory, when Y was fixed, the contribution of the binaural system appeared negligible, while fixing rho did not have this effect. 相似文献
13.
Rare earth element substituted bismuth ferrites (BiFeO3) are of enormous importance as magnetoelectric materials. The polycrystalline samples of Bi
x
La1−x
FeO3 (x=0, 0.2, 0.4, 0.6, 0.8) were prepared by solid-state reaction using standard ceramic method. The single-phase formation of
these compounds was confirmed by X-ray diffraction (XRD) studies. The samples with x=0, 0.2, 0.4, 0.6 are found to be orthorhombic while the sample with x=0.8 is triclinic. The dielectric constant (ε′) and dissipation factor (tan δ) were measured in the frequency range 100 Hz
to 1 MHz at room temperature and as a function of temperature at certain fixed frequencies (1 kHz, 10 kHz, 100 kHz, 1 MHz).
All the samples showed dielectric dispersion. The dielectric constant with temperature shows a broad peak; the peak temperature
shifts with frequency which reflects the relaxor-type behavior. The peak above 600 K in the measured temperature range corresponds
to antiferromagnetic ordering temperature (Néel temperature). The broadness of the peak changes with composition. The ac conductivity
as well as ε′ are found to be maximum for the sample x=0.2 at room temperature. 相似文献
14.
V. Baru J. Haidenbauer C. Hanhart A. Kudryavtsev P. Moskal J. Speth 《The European Physical Journal A - Hadrons and Nuclei》1999,6(4):445-450
The near threshold behaviour of the reaction cross section for pp→ppη′, recently measured in experiments at COSY and SATURNE, is analyzed. The interaction in the pp as well as in the η′
p final states is taken into account. The suppression of the total cross section for this process at excess energies Q < 3 MeV observed in these experiments is interpreted as an evidence for a strong repulsive η′
p interaction.
Received: 26 May 1999 / Revised version: 8 July 1999 相似文献
15.
Two-photon optogalvanic transitions in Ar glow discharge with Nd: YAG laser pumped dye laser excitation in the frequency range
13520–16520 cm−1 has been studied using linear and circular polarization. The intensities of two-photon optogalvanic transitions are very
sensitive to changes in the incident laser power which is not the case with one-photon transitions. Intensity ratio for circular
and linear polarized light for two photon transitions 6s′[1/2]°1←4s[3/2]°2, 6s′[1/2]°0←4s[3/2]°2, and 5d[1/2]°0←4s[3/2]°2, 5d[1/2]°1←4s[3/2]°2 are quite different from the other two-photon transitions. This has been explained as due to near one photon resonance
of 4p′[3/2]1 level for the first pair and 4p′[1/2]1 for the second pair of transitions. The ratio of optogalvanic intensity for circular to linear polarized light has
been theoretically estimated and compared with the observed results. 相似文献
16.
Using the configuration interaction Pauli-Fock including core polarization (CIPFCP)
approach we have calculated absolute total and partial cross sections for photoionization
of excited
mp
5(m + 1)p J = 0−3
levels in Ar, Kr and Xe (m = 3−5) near threshold. Particular emphasis is
paid to the lineshapes of the odd mp
1/25
n(s/d)′
autoionizing
resonances and their variation with the character of the intermediate excited
J = 0−3 state. For selected intermediate levels of Ar and Kr the
computed cross sections are compared with laser spectroscopic measurements; good agreement
between the theoretical and experimental lineshapes and branching ratios for different
resonances is observed. 相似文献
17.
In this paper, a broadband reflector exhibiting a flattened bandstop spectral response is proposed by using a multilayered
grating structure possessing multi-subpart profile. It is shown that with the properly configured profile and a strongly modulated
grating layer, in transverse electric (TE) polarized wave the presented reflector experimentally demonstrated a 240 nm-wide
reflection spectrum from 1.56 to 1.8 μm, very high reflectivity (>97%), and a low sensitivity to incident angle at the range
of −13.8°<θ<+14°. Effects of deviation from the design parameters on the performance of the reflector are also illustrated, and a reasonably
good tolerance of fabrication error is exhibited in the proposed device. 相似文献
18.
A. A. Ovchinnikov M. Ya. Ovchinnikova E. A. Plekhanov 《Journal of Experimental and Theoretical Physics》1999,88(2):356-369
The phase diagram, nature of the normal state pseudogap, type of the Fermi surface, and behavior of the superconducting gap
in various cuprates are discussed in terms of a correlated state with valence bonds. The variational correlated state, which
is a band analogue of the Anderson (RVB) states, is constructed using local unitary transformations. Formation of valence
bonds causes attraction between holes in the d-channel and corresponding superconductivity compatible with antiferromagnetic spin order. Our calculations indicate that
there is a fairly wide range of doping with antiferromagnetic order in isolated CuO2 planes. The shape of the Fermi surface and phase transition curve are sensitive to the value and sign of the hopping interaction
t′ between diagonal neighboring sites. In underdoped samples, the dielectrization of various sections of the Fermi boundary,
depending on the sign of t′, gives rise to a pseudogap detected in photoemission spectra for various quasimomentum directions. In particular, in bismuth-and
yttrium-based ceramics (t′>0), the transition from the normal state of overdoped samples to the pseudogap state of underdoped samples corresponds to
the onset of dielectrization on the Brillouin zone boundary near k=(0,π) and transition from “large” to “small” Fermi surfaces. The hypothesis about s-wave superconductivity of La-and Nd-based ceramics has been revised: a situation is predicted when, notwithstanding the d-wave symmetry of the superconducting order parameter, the excitation energy on the Fermi surface does not vanish at all points
of the phase space owing to the dielectrization of the Fermi boundary at k
x=±
k
y. The model with orthorhombic distortions and two peaks on the curve of T
c versus doping is discussed in connection with experimental data for the yttrium-based ceramic.
Zh. éksp. Teor. Fiz. 115, 649–674 (February 1999) 相似文献
19.
The reaction pn↦dφ is studied within a covariant boson exchange model. The behavior of polarization observables being accessible in forthcoming
experiments near threshold is predicted.
Received: 13 February 2001 / Accepted: 25 March 2002 相似文献
20.
L. Lis 《Il Nuovo Cimento D》1990,12(7):935-940
Summary In this report investigations are presented of laser generations at 3391 nm and 3391 and 7699 nm, or rather of changes induced
by them in populations of the 5s′ [1/2]
1
0
, 4p′[3/2]2 and 3d′[5/2]
3
0
levels, depending upon the angle of the tilted mirror of the He−Ne laser system. This writer has discovered that the above
laser generations develop at a strongly tilted mirror, when the beam reflected from one mirror, in order to reach the other,
has to be reflected many times on the inside walls of the discharge tube.
The work was supported by CPBR 8.14. 相似文献