1207 research outputs found
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Random percolation as a gauge theory
Get PDFThree-dimensional bond or site percolation theory on a lattice can be interpreted as a gauge theory in which the Wilson loops are viewed as counters of topological linking with random clusters. Beyond the percolation threshold large Wilson loops decay with an area law and show the universal shape effects due to flux tube quantum fluctuations like in ordinary confining gauge theories. Wilson loop correlators define a non-trivial spectrum of physical states of increasing mass and spin, like the glueballs of ordinary gauge theory. The crumbling of the percolating cluster when the length of one periodic direction decreases below a critical threshold accounts for the finite temperature deconfinement, which belongs to 2-D percolation universality class
Finite-Time Current Probabilities in the Asymmetric Exclusion Process on a Ring
Get PDFWe calculate the time-dependent probability of non-zero current through a selected bond in the totally asymmetric exclusion process with periodic boundary conditions. For specific initial conditions corresponding to the minimal probability of non-zero current, we derive an explicit analytical expression which is valid for arbitrary time intervals
Studying glueball masses in non-Abelian LGT with the LW algorithm
Get PDFWe address a study of glueball masses in the confining regime of SU(2) in D = 3 using an algo-rithm inspired by the multi-level scheme. Our method, which exploits the locality of the action to achieve high precision results, is based on a technique already used for compact QED, and gen-eralises it to the non-Abelian case. We discuss the main features of this method, in comparison with other algorithms that have been used in similar studies
Miscellanea Hibernica: 1. Old Irish tráigid (ebbs, recedes). 2. The Simplex serbaid. 3. do-maisi and a Detail of Syncope
Get PDFLong Cycles in a Perturbed Mean Field Model of a Boson Gas
Get PDFIn this paper we give a precise mathematical formulation of the relation between Bose condensation and long cycles and prove its validity for the perturbed mean field model of a Bose gas. We decompose the total density ρ = ρ_short + ρ_long into the number density of particles belonging to cycles of finite length (ρ_short) and to infinitely long cycles (ρ_long) in the thermodynamic limit. For this model we prove that when there is Bose condensation, ρ_long is different from zero and identical to the condensate density. This is achieved through an application of the theory of large deviations. We discuss the possible equivalence of ρ_long =/= 0 with off-diagonal long range order and winding paths that occur in the path integral representation of the Bose gas
Comparing the Nambu-Goto string with LGT results
Get PDFWe discuss a way to evaluate the full prediction for the interquark potential which is expected from the effective Nambu-Goto string model. We check the correctness of the prescription reproducing the results obtained with the zeta function regularization for the first two perturbative orders. We compare the predictions with existing Monte Carlo data for the (2+1) dimensional Z_2, SU(2) and SU(3) gauge theories: in the low temperature regime, we find good agreement for large enough interquark distances, but an increasing mismatch between theoretical predictions and numerical results is observed as shorter and shorter distances are investigated. On the contrary, at high temperatures (approaching the deconfinement transition from below) a remarkable agreement between Monte Carlo data and the expectations from the Nambu-Goto effective string is observed for a wide range of interquark distances
Waves on noncommutative spacetimes
Get PDFWaves on “commutative” spacetimes like R^d are elements of the commutative algebra C^0(R^d) of functions on R^d . When C^0(R^d) is deformed to a noncommutative algebra A_θ(R^d) with deformation parameter θ (A_0(R^d) = C^0(R^d)), waves being its elements, are no longer complex-valued functions on R^d . Rules for their interpretation, such as measurement of their intensity, and energy, thus need to be stated. We address this task here. We then apply the rules to interference and diffraction for d ≤ 4 and with time-space noncommutativity. Novel phenomena are encountered. Thus when the time of observation T is so brief that T ≤ 2θw, where w is the frequency of incident waves, no interference can be observed. For larger times, the interference pattern is deformed and depends on θw/T . It approaches the commutative pattern only when θw/T → 0. As an application, we discuss interference of star light due to cosmic strings
Zero is not a Four-Letter Word: Studies in the Evolution of Language
Get PDFWe examine a model genetic system that has features of both genetic programming and genetic regulatory networks, to show how various forms of degeneracy in the genotype-phenotype map can induce complex and subtle behaviour in the dynamics that lead to enhanced evolutionary robustness and can be fruitfully described in terms of an elementary algorithmic “language”
