共查询到20条相似文献,搜索用时 78 毫秒
1.
Duplantier B 《Physical review letters》2000,84(7):1363-1367
The multifractal (MF) distribution of the electrostatic potential near any conformally invariant fractal boundary, like a critical O(N) loop or a Q-state Potts cluster, is solved in two dimensions. The dimension &fcirc;(straight theta) of the boundary set with local wedge angle straight theta is &fcirc;(straight theta) = pi / straight theta-25-c / 12 (pi-straight theta)(2) / straight theta(2pi-straight theta), with c the central charge of the model. As a corollary, the dimensions D(EP) of the external perimeter and D(H) of the hull of a Potts cluster obey the duality equation (D(EP)-1) (D(H)-1) = 1 / 4. A related covariant MF spectrum is obtained for self-avoiding walks anchored at cluster boundaries. 相似文献
2.
Brünger C Assaad FF Capponi S Alet F Aristov DN Kiselev MN 《Physical review letters》2008,100(1):017202
We consider a spin-1/2 ladder with a ferromagnetic rung coupling J perpendicular and inequivalent chains. This model is obtained by a twist (theta) deformation of the ladder and interpolates between the isotropic ladder (theta=0) and the SU(2) ferromagnetic Kondo necklace model (theta = pi). We show that the ground state in the (theta, J perpendicular) plane has a finite string order parameter characterizing the Haldane phase. Twisting the chain introduces a new energy scale, which we interpret in terms of a Suhl-Nakamura interaction. As a consequence we observe a crossover in the scaling of the spin gap at weak coupling from delta/J parallel proportional, variant J perpendicular/J parallel for theta < theta c approximately 8 pi/9 to delta/J parallel proportional, variant (J perpendicular/J parallel)2 for theta > theta c. Those results are obtained on the basis of large scale quantum Monte Carlo calculations. 相似文献
3.
计算了三光子W态隐形传输令牌总线网的保真度.通过计算发现在整个量子网络通信过程中,对于给定的分析角θ,保真度仅与系数|a|2有关|随着分析角θ的增加,保真度出现最大值所对应的系数|a|2相应减小,取θ=π/4、π/2、3π/4时可使保真度达最大值1,此时对应的|a|2分别为0.724、0.5和0.276.对于给定的系数|a|,保真度仅与分析角θ有关|若|a|=0,则无论θ为何值,保真度始终为0|若|a|=|b|=0.707 1,则当θ=π/2、3π/2时保真度达最大值1. 相似文献
4.
Raidal M 《Physical review letters》2004,93(16):161801
We argue that there exists a simple relation between the quark and lepton mixings, which supports the idea of grand unification and probes the underlying robust bimaximal fermion mixing structure of still unknown flavor physics. In this framework the quark mixing matrix is a parameter matrix describing the deviation of neutrino mixing from exactly bimaximal, predicting theta(sol)+theta(C)=pi/4, where theta(C) is the Cabibbo angle, theta(atm)+theta(CKM)(23)=pi/4 and theta(MNS)(13) approximately theta(CKM)(13) approximately O(lambda(3)), in perfect agreement with experimental data. Both non-Abelian and Abelian flavor symmetries are needed for such a prediction to be realistic. An example flavor model capable of explaining this flavor mixing pattern and inducing the measured quark and lepton masses is outlined. 相似文献
5.
Friedland A 《Physical review letters》2000,85(5):936-939
We point out that for solar neutrino oscillations with the mass-squared difference of Deltam(2) approximately 10(-10)-10(-9) eV(2), i.e., in the so-called vacuum oscillation range, the solar matter effects are non-negligible, particularly for the low energy pp neutrinos. One consequence of this is that the values of the mixing angle straight theta and pi/2-straight theta are not equivalent, making it necessary to consider the entire physical range of the mixing angle 0=straight theta=pi/2 when determining the allowed values of the neutrino oscillation parameters. 相似文献
6.
He Q Insler J Muramatsu H Park CS Thorndike EH Yang F Coan TE Gao YS Artuso M Blusk S Butt J Li J Menaa N Mountain R Nisar S Randrianarivony K Sia R Skwarnicki T Stone S Wang JC Zhang K Bonvicini G Cinabro D Dubrovin M Lincoln A Asner DM Edwards KW Briere RA Ferguson T Tatishvili G Vogel H Watkins ME Rosner JL Adam NE Alexander JP Cassel DG Duboscq JE Ehrlich R Fields L Gibbons L Gray R Gray SW Hartill DL Heltsley BK Hertz D Jones CD Kandaswamy J Kreinick DL Kuznetsov VE Mahlke-Krüger H 《Physical review letters》2008,100(9):091801
We present measurements of D--> KS0 pi and D--> KL0 pi branching fractions using 281 pb(-1) of psi(3770) data at the CLEO-c experiment. We find that B(D0--> KS0 pi 0) is larger than B(D0--> KL0 pi 0), with an asymmetry of R(D0)=0.108+/-0.025+/-0.024. For B(D+--> KS0 pi+) and B(D+--> KL0 pi+), we observe no measurable difference; the asymmetry is R(D+)=0.022+/-0.016+/-0.018. The D0 asymmetry is consistent with the value based on the U-spin prediction A(D0--> K0 pi 0)/A(D0--> K0 pi 0)=-tan2 theta C, where theta C is the Cabibbo angle. 相似文献
7.
We explore the possibility of observing the anticharmed pentaquark state from the theta(c)npi(+) decay of B mesons produced in B-factory experiments. We first show that the observed branching ratio of the B(+) to lambda(-)(c)p pi(+), as well as its open histograms, can be remarkably well explained by assuming that the decay proceeds first through the pi(+) D(0) (or D(*0)) decay, and then through the subsequent decay of the virtual D(0) or D(*0) mesons to lambda(-)(c)p. We then note that the theta(c)can be similarly produced when the virtual D(0) or D(*0) decay into an antinucleon and a theta(c). Combining the present theoretical estimates for the ratio g(DNlambda(c))/g(DNtheta(c)) approximately 13 and g(D*Ntheta(c)) approximately 1/3g(DNtheta(c)), we find that the anticharmed pentaquark theta(c), which was predicted to be bound by several model calculations, can be produced via B(+)--> theta(c)npi(+), and be observed from the B-factory experiments through the weak decay of theta(c)--> pK(+) pi(-) pi(-). 相似文献
8.
Zhu LY Arrington J Averett T Beise E Calarco J Chang T Chen JP Chudakov E Coman M Clasie B Crawford C Dieterich S Dohrmann F Dutta D Fissum K Frullani S Gao H Gilman R Glashausser C Gomez J Hafidi K Hansen JO Higinbotham DW Holt RJ De Jager CW Jiang X Kinney E Kramer K Kumbartzki G LeRose J Liyanage N Mack D Markowitz P McCormick K Meekins D Meziani ZE Michaels R Mitchell J Nanda S Potterveld D Ransome R Reimer PE Reitz B Saha A Schulte EC Seely J Sirca S Strauch S Sulkosky V Vlahovic B 《Physical review letters》2003,91(2):022003
We have measured the differential cross section for the gamman-->pi(-)p and gammap-->pi(+)n reactions at theta(c.m.)=90 degrees in the photon energy range from 1.1 to 5.5 GeV at Jefferson Lab (JLab). The data at E(gamma) greater, similar 3.3 GeV exhibit a global scaling behavior for both pi(-) and pi(+) photoproduction, consistent with the constituent counting rule and the existing pi(+) photoproduction data. Possible oscillations around the scaling value are suggested by these new data. The data show enhancement in the scaled cross section at a center-of-mass energy near 2.2 GeV. The cross section ratio of exclusive pi(-) to pi(+) photoproduction at high energy is consistent with the prediction based on one-hard-gluon-exchange diagrams. 相似文献
9.
Pribulova Z Klein T Marcus J Marcenat C Levy F Park MS Lee HG Kang BW Lee SI Tajima S Lee S 《Physical review letters》2007,98(13):137001
The anisotropic field dependence of the Sommerfeld coefficient gamma has been measured down to B-->0 by combining specific heat and Hall probe magnetization measurements in MgB2 single crystals. We find that gamma(B,theta) is the sum of two contributions arising from the sigma and pi band, respectively. We show that gammasigma(B,theta)=B/Bc2(theta) where Bc2(theta)=Bc2ab/sqrt[sin2theta+Gamma2cos2theta] with Gamma approximately 5.4 (theta being the angle between the applied field and the c axis) and gammapi(B,theta)=gammapi(B)=B/Bpi(B). The "critical field" of the pi band Bpi is fully isotropic but field dependent increasing from approximately 0.25 T for B< or =0.1 T up to 3 T approximately Bc2c for B-->3 T. Because of the coupling of the two bands, superconductivity survives in the pi band up to 3 T but is totally destroyed above for any orientation of the field. 相似文献
10.
Using an approach to analyze the theta dependence of systems with a theta term we recently proposed, the critical behavior of CP(10 at theta=pi is studied. We find a region outside the strong coupling regime where Haldane's conjecture is verified. The critical line, however, does not belong to the universality class of the Wess-Zumino-Novikov-Witten model at topological coupling k=1 since it shows continuously varying critical exponents. 相似文献
11.
D.V. Dmitriev V.Ya. Krivnov A.A. Ovchinnikov 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,14(1):91-97
We study the spin ladder model with interactions between spins on neighboring rungs. The model Hamiltonian with the exact
singlet ground state degenerated with ferromagnetic state is obtained. The singlet ground state wave function has a special
recurrent form and depends on two parameters. Spin correlations in the singlet ground state show double-spiral structure with
period of spirals equals to the system size. For special values of parameters they have exponential decay. The spectrum of
the model is gapless and there are asymptotically degenerated excited states for special values of parameters in the thermodynamic
limit.
Received 7 May 1999 相似文献
12.
We consider the conductivity sigma of graphene with negligible intervalley scattering at half filling. We derive the effective field theory, which, for the case of a potential disorder, is a symplectic-class sigma model including a topological term with theta=pi. As a consequence, the system is at a quantum critical point with a universal value of the conductivity of the order of e(2)/h. When the effective time-reversal symmetry is broken, the symmetry class becomes unitary, and sigma acquires the value characteristic for the quantum Hall transition. 相似文献
13.
14.
采用从基态到第一激发态为双激光场驱动的物理模型,对梯形三能级系统中自发辐射的相干控制进行了分析,通过变换驱动激光场之间的相对相位得到了一些主要结果.共振激发时,谱线呈现出三个谱峰的对称形式.当初始相位相同时,两边辐射峰值较高而中间峰值较低.随着初相位差的增加,两边谱峰之间的距离逐渐增大,谱线的高度逐渐下降,中心谱线的高度随着初始相位差的增加逐渐增大,宽度逐渐变小,直至成为一条较为尖锐的线,实现了对两边谱峰的完全抑制效应.采用下能级为双激光场激发的梯-型三能级系统,通过变换激光场之间的相对相位,实现了对激发态自发辐射的量子相干控制,观察到自发辐射光谱的抑制及谱线的猝灭等效应. 相似文献
15.
B E Mulligan L S Goodman D P Gleisner M L Faupel 《The Journal of the Acoustical Society of America》1985,77(3):1141-1154
The dependence of binaural loudness summation on interaural phase of tones ranging between 250 and 1400 Hz was investigated in a series of experiments using a loudness-matching procedure. Observers matched loudness of monaural-binaural and binaural-binaural pairs of alternating tones by adjusting the amplitude of one of the two. Adjustable and reference components of each tone pair were equal in frequency and were varied independently in interaural phase angle through the range +/- 177 degrees. For each tone frequency, steps in loudness summation of approximately 3 dB were obtained in the vicinity of a constant value of phase angle, theta t, which depends on the Hornbostel-Wertheimer constant (tau H) according to the relations theta t = 2 pi f tau H for tones of low frequency (f less than or equal to 1/2 tau H), and theta t = 2 pi(1 - f tau H) for tones of higher frequency (1/2 tau H less than or equal to f less than or equal to 1/tau H). Spatial relationships among alternating tones observed in the above conditions covaried with relative loudness in a complex manner, but exhibited qualitative changes in the vicinity of theta t. 相似文献
16.
Balestra F Bedfer Y Bertini R Bland LC Brenschede A Brochard F Bussa MP Choi S Colantoni ML Dressler R Dzemidzic M Faivre JC Ferrero A Ferrero L Foryciarz J Fröhlich I Frolov V Garfagnini R Grasso A Heinz S Jacobs WW Kühn W Maggiora A Maggiora M Manara A Panzieri D Pfaff HW Piragino G Popov A Ritman J Salabura P Tchalyshev V Tosello F Vigdor SE Zosi G;DISTO Collaboration 《Physical review letters》2002,89(9):092001
Total and differential cross sections for the exclusive reaction pp-->pp rho observed via the pi(+)pi(-) decay channel have been measured at p(beam)=3.67 GeV/c. The observed total meson production cross section is determined to be (23.4+/-0.8+/-8) mu b and is significantly lower than typical cross sections used in model calculations for heavy-ion collisions. The differential cross sections measured indicate a strong anisotropy (approximately cos(theta(CM)(rho)) in the rho(0) meson production. 相似文献
17.
Optical implementation of orthogonal phase-code multiplexing 总被引:1,自引:0,他引:1
We propose a new optical implementation of orthogonal phase-code multiplexing in which an arbitrary phase shift of theta or theta +pi is used in the reference beam instead of 0 or pi as in the conventional method. To compare the new and the conventional methods, we employ a 2-bit orthogonal phase code and store two binary-data images in a BaTiO(3) crystal with each method. We also employ numerical methods to simulate the 2-bit phase-code multiplexing and show that the signal-to-noise ratio in the restored images is improved by more than one order of magnitude in the new method in our experimental conditions. 相似文献
18.
S K Misra 《Journal of magnetic resonance (San Diego, Calif. : 1997)》1999,140(1):179-188
Details are given of a procedure to evaluate the spin-Hamiltonian (SH) parameters and the linewidth from a polycrystalline EPR spectrum by using a least-squares fitting (LSF) technique in conjunction with numerical diagonalization of the SH matrix. The required resonance line positions are computed rather quickly using a homotopy technique, in which the position at an external magnetic field (B) orientation (theta, phi) is used as the initial value in a LSF procedure to estimate the position at an infinitesimally close B-orientation, (theta + deltatheta, phi + deltaphi). The resonance line positions are calculated successively in this procedure for all orientations of B over a grid of (theta, phi) values for the unit sphere. The eigenvectors of the SH matrix are used to calculate the intensities of the EPR lines exactly for each orientation of B. Details are given of how to compute rigorously the first and second derivatives of the chi(2)-function with respect to the SH parameters and the linewidth using the eigenvalues and eigenvectors of the spin-Hamiltonian matrix for a polycrystalline spectrum required in the LSF procedure. It is explained how this technique is generalized to include two or more magnetically inequivalent paramagnetic species, as well as how it is used for the simulation of other EPR-related spectra. The procedure is illustrated by evaluation of the Mn(2+) SH parameters and Lorentzian linewidth from the 249.9-GHz EPR spectrum of Mn(gamma-picoline)(4)I(2). 相似文献
19.
M. Hafez S. A. Jafari 《The European Physical Journal B - Condensed Matter and Complex Systems》2010,78(3):323-333
We use perturbative continuous unitary transformations (PCUT) to study
the one dimensional extended ionic Hubbard model (EIHM) at half-filling in the band insulator
region. The extended ionic Hubbard model, in addition to the usual ionic
Hubbard model, includes an inter-site nearest-neighbor (n.n.) repulsion, V. We consider
the ionic potential as unperturbed part of the Hamiltonian, while the hopping and interaction
(quartic) terms are treated as perturbation.
We calculate total energy and ionicity in the ground state.
Above the ground state, (i) we calculate the single particle excitation spectrum by adding
an electron or a hole to the system; (ii) the coherence-length
and spectrum of electron-hole excitation are obtained.
Our calculations reveal that for V = 0, there are two triplet bound state modes and three
singlet modes, two anti-bound states and one bound state, while for finite values
of V there are four excitonic bound states corresponding to two singlet and two triplet modes.
The major role of on-site Coulomb repulsion U is to split singlet and triplet
collective excitation branches, while V tends to pull the singlet branches below
the continuum to make them bound states. 相似文献
20.
D-theory provides an alternative lattice regularization of the 2D CP(N-1) quantum field theory in which continuous classical fields emerge from the dimensional reduction of discrete SU(N) quantum spins. Spin ladders consisting of n transversely coupled spin chains lead to a CP(N-1) model with a vacuum angle theta=npi. In D-theory no sign problem arises and an efficient cluster algorithm is used to investigate theta-vacuum effects. At theta=pi there is a first order phase transition with spontaneous breaking of charge conjugation symmetry for CP(N-1) models with N>2. 相似文献