关键词：
05.70.Jk Critical point phenomena;64.60.i General studies of phase transitions;75.40.Mg Numerical simulation studies
摘要：
We derive exact results for several thermodynamic quantities of the O
(
n
) symmetric
field theory in the limit
in a finite d-dimensional hypercubic geometry with periodic boundary conditions. Corresponding results are derived for an O
(
n
) symmetric
model on a finite d-dimensional lattice with a finite-range interaction. The leading finite-size effects near Tc of the field-theoretic model are compared with those of the lattice model. For 2 <
d
< 4, the finite-size scaling functions are verified to be universal. For d
> 4, significant lattice effects are found. Finite-size scaling in its usual simple form does not hold for d
> 4 but remains valid in a generalized form with two reference lengths. The finite-size scaling functions of the
field theory turn out to be nonuniversal whereas those of the
lattice model are independent of the nonuniversal model parameters. In particular, the field-theoretic model exhibits finite-size effects whose leading exponents differ from those of the lattice model. The widely accepted lowest-mode approach is shown to fail for both the field-theoretic and the lattice model above four dimensions.
作者机构：
[Wiedemann, U.A.] Inst. für Theoretische Physik, Universität Regensburg, D-93040 Regensburg, Germany;Faculty of Mathematics and Physics, Comenius University, Mlynská Dolina, SK-84215 Bratislava, Slovakia;CERN, Theory Division, CH-1211 Geneve, Switzerland;Institute of Particle Physics, Hua-Zhong Normal University, Wuhan, China;[Heinz, U.] Inst. für Theoretische Physik, Universität Regensburg, D-93040 Regensburg, Germany, CERN, Theory Division, CH-1211 Geneve, Switzerland
通讯机构：
[Tomášik, B.] I;Inst. für Theoretische Physik, Universität Regensburg, Germany
摘要：
We present the Yano-Koonin-Podgoretskiǐ parametrisation of the correlation function. Compared to the conventionally used Cartesian parametrisation, this one provides more straightforward measurement of the duration of the emission process in the fireball and a clearer signal of the longitudinal expansion, which is expected in ulrarelativistic heavy ion collisions.
作者机构：
ACAD SINICA, INST HIGH ENERGY PHYS, BEIJING, PEOPLES R CHINA.;INST GRAVITAT & SPACE RES, BUCHAREST, ROMANIA.;PANJAB UNIV, DEPT PHYS, CHANDIGARH 160014, INDIA.;HUNAN EDUC INST, DEPT PHYS, CHANGSHA, HUNAN, PEOPLES R CHINA.;JOINT INST NUCL RES DUBNA, LAB HIGH ENERGIES, DUBNA, RUSSIA.
通讯机构：
[Adamovich, MI] I;INST HIGH ENERGY PHYS, ALMATY, KAZAKHSTAN.
摘要：
Angular distributions of projectile-associated He fragments from Pb induced reactions on stationary Pb target at 158 A GeV/c incident momentum are reported. The precision of the angular measurements was about ±0.01 mrad. Two emission components are appearing in the projected angular spectra of the He particles, one representing fragmentation at Fermi momentum scale, while the other one exhibits large transverse momentum transfer. By scaling with the incident momentum the angular spectra of He particles are compared with earlier reported measurements of Au on Au interactions at 11.6 A GeV/c. The pT spectrum of the He particles appears the same for the two cases.
作者机构：
[Gao-Niang L.] Department of Physics, Huazhong Normal University, Wuhan 430079, China;[Van C.-N.] Department of Chemistry, Jinzhou Normal College, Jinzhou 434100, China;[Jin-Sheng P.] Department of Physics, Huazhang Normal University, Wuhan 430079, China
通讯机构：
[Li, GX] H;HUAZHONG NORMAL UNIV,DEPT PHYS,WUHAN 430079,PEOPLES R CHINA.
摘要：
We have studied the atomic coherent population trapping in a Raman-type photoionization system with three bound states. The conditions for the system having two or one stable eigenstate are given. The influences of Fano asymmetric factors on the coherent population transfer are also analyzed. It is found that the property of the system having only one population trapping state consisting of the ground state and one excited state, can be utilized to transfer the atomic initial population into one excited state.
作者机构：
[Li, GX; Peng, JS] Department of Physics, Huazhong Normal University, Wuhan 430070, China
通讯机构：
[Li, GX] H;HUAZHONG NORMAL UNIV,DEPT PHYS,WUHAN 430070,PEOPLES R CHINA.
摘要：
We have studied the atomic coherent population trapping in the system of a two-mode quantized field interacting with a Λ-configuration multilevel atom with one lower discrete state and two sets of quasicontinuum states, or a set of quasicontinuum states and a set of true continuum states. The influence of the atom's initial preparation and the properties of the atomic upper levels on whether or not atomic coherent population trapping occurs, and the states of the field which trap the atom are analyzed.
作者机构：
[Li, GX] Huazhong Normal Univ, Dept Phys, Wuhan 430079, Peoples R China.;Queens Univ Belfast, Dept Appl Math & Theoret Phys, Belfast BT7 1NN, Antrim, North Ireland.
通讯机构：
[Li, GX] H;Huazhong Normal Univ, Dept Phys, Wuhan 430079, Peoples R China.
关键词：
光化电离系统;自电离态;相干群陷阱作用
摘要：
We investigate the atomic coherent population trapping in the system of two-mode quantized field interacting with a Λ-configuration atom with two lower bound states, one autoionizing state and a flat atomic continuum. The states of the field which traps the atom in its two lower bound states are given and the influence of the field induced continuum structure is examined.
期刊：
EUROPEAN PHYSICAL JOURNAL B,1997年102(2):233-237 ISSN：1434-6028
通讯作者：
Li, GX
作者机构：
[Peng, JS; Li, GX] HUAZHONG NORMAL UNIV, DEPT PHYS, WUHAN 430070, PEOPLES R CHINA.;[Li, GX] CHINA CTR ADV SCI & TECHNOL, WORLD LAB, POB 8730, BEIJING 100080, PEOPLES R CHINA.
通讯机构：
[Li, GX] C;CHINA CTR ADV SCI & TECHNOL, WORLD LAB, POB 8730, BEIJING 100080, PEOPLES R CHINA.
摘要：
The atomic coherent population trapping in the system of an atom with one ground state, a pair of excited states and a set of continuum states, interacting with two temporally separated sets of laser pulses with different phases is investigated. The relative phases of laser pulses on the amount of atomic populations trapped in the three bound states and the efficiency of population transfer are analyzed.
