3,214 research outputs found
Equal-time correlation function for directed percolation
We suggest an equal-time n-point correlation function for systems in the
directed percolation universality class which is well defined in all phases and
independent of initial conditions. It is defined as the probability that all
points are connected with a common ancestor in the past by directed paths.Comment: LaTeX, 12 pages, 8 eps figure
Ageing, dynamical scaling and conformal invariance
Building on an analogy with conformal invariance, local scale transformations
consistent with dynamical scaling are constructed. Two types of local scale
invariance are found which act as dynamical space-time symmetries of certain
non-local free field theories. The scaling form of two-point functions is
completely fixed by the requirement of local scale invariance. These
predictions are confirmed through tests in the 3D ANNNI model at its Lifshitz
point and in ageing phenomena of simple ferromagnets, here studied through the
kinetic Ising model with Glauber dynamics.Comment: Latex2e, 12 pages, 3 figures. Talk given at TH2002, Paris July 200
Large impacts in the Baltic shield with special attention to the Uppland structure
Within the Baltic Shield several very large structures have been identified and are suspected to be of meteorite impact origin. Some of these deeply eroded circular features are presented with special attention to the Uppland structure, where several indications point toward an impact origin in the mid-Proterozoic. The structures exceed 100 km in diameter and the topographic expression is inferior or absent. An arcuate arrangement of lithologies occurs around the margin of the structures and the central regions show conform magnetic and positive gravity anomalies. The Uppland structure is approximately 320 km in diameter as expressed by morphological, geological, and geophysical concentric patterns. The central part is topographically remarkably flat and is characterized by an unusual irregular fracture pattern. A subcircular central tonalite with density of 2.81 Mg(sup -3) gives a positive gravity anomaly of 35 mgal and the gravimetric profile is very similar to that of Manicouagan and Vredefort. The tonalite constitutes a huge antiform, 80 km in diameter, probably representing a 12-km structural uplift of infracrustal rocks. The flancs of the tonalite are characterized by recrystallized pseudotachylitic breccia dykes and breccia zones. Around the central parts amphibolite-grade metamorphic rocks appear as large fragments within a fine-grained granite interpreted as a thermally annealed melt rock. Several occurrences of breccia dykes and breccia-bearing melts have been identified about 100 km from the gravimetric center of the structure. Impact-related ore deposits are located around the margin of the structure and are interpreted as preexisting downfaulted iron formations, and deposits formed from remobilization of these preimpact occurrences. The so-called ball ores are interpreted to have formed by fluid injection similar to the formation of breccia dykes. The extensive hydrothermal alteration along the outer margin of the structure have created extreme soda and K-enriched rocks ('leptites') from preexisting gneiss granites and supracrustal sedimentary gneisses
Thermal effects in the magnetic Casimir-Polder interaction
We investigate the magnetic dipole coupling between a metallic surface and an
atom in a thermal state, ground state and excited hyperine state. This
interaction results in a repulsive correction and - unlike the electrical
dipole contribution - depends sensitively on the Ohmic dissipation in the
material
Impact cratering record of Fennoscandia
A compilation of circular topographic, morphological, or geophysical structures in Fennoscandia and adjacent areas reveals 62 craterform structures of which 15 appear to be of extraterrestrial origin due to meteorite impact. The majority of the structures are probable and possible impact craters for which there is not yet sufficient proof for impact origin. Four of the proven impact craters contain large volumes of impact melt and many other features of intense shock metamorphism. The age of recognized impact craters vary from prehistoric to late Precambrian. We review the Fennoscandian impact cratering record giving examples of geophysical signatures of impact craters
From kinetic theory to dissipative fluid dynamics
We present the results of deriving the Israel-Stewart equations of
relativistic dissipative fluid dynamics from kinetic theory via Grad's
14-moment expansion. Working consistently to second order in the Knudsen
number, these equations contain several new terms which are absent in previous
treatments.Comment: 7 pages, proceedings of the Erice School on Nuclear Physics "Heavy
Ion collisions from the Coulomb Barrier up to the Quark Gluon Plasma", Erice,
Sicily, Sep. 16 - 24, 200
On the predictive power of Local Scale Invariance
Local Scale Invariance (LSI) is a theory for anisotropic critical phenomena
designed in the spirit of conformal invariance. For a given representation of
its generators it makes non-trivial predictions about the form of universal
scaling functions. In the past decade several representations have been
identified and the corresponding predictions were confirmed for various
anisotropic critical systems. Such tests are usually based on a comparison of
two-point quantities such as autocorrelation and response functions. The
present work highlights a potential problem of the theory in the sense that it
may predict any type of two-point function. More specifically, it is argued
that for a given two-point correlator it is possible to construct a
representation of the generators which exactly reproduces this particular
correlator. This observation calls for a critical examination of the predictive
content of the theory.Comment: 17 pages, 2 eps figure
Local scale invariance in the parity conserving nonequilibrium kinetic Ising model
The local scale invariance has been investigated in the nonequilibrium
kinetic Ising model exhibiting absorbing phase transition of PC type in 1+1
dimension. Numerical evidence has been found for the satisfaction of this
symmetry and estimates for the critical ageing exponents are given.Comment: 8 pages, 2 figures (IOP format), final form to appear in JSTA
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