242 research outputs found
On the Segregation Phenomenon in Complex Langevin Simulation
In the numerical simulation of certain field theoretical models, the complex
Langevin simulation has been believed to fail due to the violation of
ergodicity. We give a detailed analysis of this problem based on a toy model
with one degree of freedom (). We find that the failure is
not due to the defect of complex Langevin simulation itself, but rather to the
way how one treats the singularity appearing in the drift force. An effective
algorithm is proposed by which one can simulate the behaviour of
the expectation value in the small limit.Comment: (20 pages + 8 figures on request). Siegen Si-93-8, Tokuyama TKYM-93-
Determination of the Critical Point and Exponents from short-time Dynamics
The dynamic process for the two dimensional three state Potts model in the
critical domain is simulated by the Monte Carlo method. It is shown that the
critical point can rigorously be located from the universal short-time
behaviour. This makes it possible to investigate critical dynamics
independently of the equilibrium state. From the power law behaviour of the
magnetization the exponents and are determined.Comment: 6 pages, 4 figure
Universality and Scaling in Short-time Critical Dynamics
Numerically we simulate the short-time behaviour of the critical dynamics for
the two dimensional Ising model and Potts model with an initial state of very
high temperature and small magnetization. Critical initial increase of the
magnetization is observed. The new dynamic critical exponent as well
as the exponents and are determined from the power law
behaviour of the magnetization, auto-correlation and the second moment.
Furthermore the calculation has been carried out with both Heat-bath and
Metropolis algorithms. All the results are consistent and therefore
universality and scaling are confirmed.Comment: 14 pages, 14 figure
Universal Short-time Behaviour of the Dynamic Fully Frustrated XY Model
With Monte Carlo methods we investigate the dynamic relaxation of the fully
frustrated XY model in two dimensions below or at the Kosterlitz-Thouless phase
transition temperature. Special attention is drawn to the sublattice structure
of the dynamic evolution. Short-time scaling behaviour is found and
universality is confirmed. The critical exponent is measured for
different temperature and with different algorithms.Comment: 18 pages, LaTeX, 8 ps-figure
Dynamic SU(2) Lattice Gauge Theory at Finite Temperature
The dynamic relaxation process for the (2+1)--dimensional SU(2) lattice gauge
theory at critical temperature is investigated with Monte Carlo methods. The
critical initial increase of the Polyakov loop is observed. The dynamic
exponents and as well as the static critical exponent
are determined from the power law behaviour of the Polyakov loop, the
auto-correlation and the second moment at the early stage of the time
evolution. The results are well consistent and universal short-time scaling
behaviour of the dynamic system is confirmed. The values of the exponents show
that the dynamic SU(2) lattice gauge theory is in the same dynamic universality
class as the dynamic Ising model.Comment: 10 pages with 2 figure
The short-time behaviour of a kinetic Ashkin-Teller model on the critical line
We simulate the kinetic Ashkin-Teller model with both ordered and disordered
initial states, evolving in contact with a heat-bath at the critical
temperature. The power law scaling behaviour for the magnetic order and
electric order are observed in the early time stage. The values of the critical
exponent vary along the critical line. Another dynamical exponent
is also obtained in the process.Comment: 14 pages LaTeX with 4 figures in postscrip
The short-time Dynamics of the Critical Potts Model
The universal behaviour of the short-time dynamics of the three state Potts
model in two dimensions at criticality is investigated with Monte Carlo
methods. The initial increase of the order is observed. The new dynamic
exponent as well as exponent and are determined. The
measurements are carried out in the very beginning of the time evolution. The
spatial correlation length is found to be very short compared with the lattice
size.Comment: 6 pages, 3 figure
Eiszeitliche Ablagerungen in Hochlagen des Süntels (Süd-Hannover) und seinen Karstschlotten
Aus dem Karstgebiet des Riesenberges im Süntel werden hochgelegene kies- und steinführende Ablagerungen verschiedenen Alters beschrieben. Außer kiesführenden Höhlensedimenten präglazialen Alters treten kiesführende Ablagerungen auf, die eiszeitlich entstanden sind. Während die Kies- und Steinanteile der präglazialen Ablagerungen aus lokalen (Kalkstein des Malm) und z. T. ortsfremden Komponenten (Sandstein des Wealden) bestehen, enthalten die jüngeren Ablagerungen zusätzlich Kiesanteile aus nordisch-skandinavischen Gesteinen sowie resedimentierten Weserkies. Die eiszeitlichen Ablagerungen wurden im Kammbereich sowie in Karsthöhlen abgelagert.Gravel deposits positioned in high altitude areas of Süntel Mountains are described from the carst area of Riesenberg. Not only cave gravel of pre-glacial age, but also those of glacial age occur. While the pre-glacial deposits comprise local, but xenotopic components, the younger ones display also material of northern derivation as well as reworked gravels from the Weser-River. The sediments were deposited both in caves and at summit region of the Süntel Mountains. Conditions of deposition and age relation to the glaciations are discussed
Dynamic Approach to the Fully Frustrated XY Model
Using Monte Carlo simulations, we systematically investigate the
non-equilibrium dynamics of the chiral degree of freedom in the two-dimensional
fully frustrated XY model. The critical initial increase of the staggered
chiral magnetization is observed. By means of the short-time dynamics approach,
we estimate the second order phase transition temperature and all the
dynamic and static critical exponents , z, and .Comment: 5 pages with 6 figures include
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