510 research outputs found
High Temperature 3D QCD: Dimensional Reduction at Work
We investigate the three-dimensional SU(3) gauge theory at finite temperature
in the framework of dimensional reduction. The large scale properties of this
theory are expected to be conceptually more complicated than in four
dimensions. The dimensionally reduced action is computed in closed analytical
form. The resulting effective two-dimensional theory is studied numerically
both in the electric and magnetic sector. We find that dimensional reduction
works excellently down to temperatures of 1.5 times the deconfinement phase
transition temperature and even on rather short length scales. We obtain strong
evidence that for , even at high temperature the colour averaged
potential is represented by the exchange of a single state, at variance with
the usual Debye screening picture involving a pair of electric gluons.Comment: 27 page
A really simple approximation of smallest grammar
In this paper we present a really simple linear-time algorithm constructing a
context-free grammar of size O(g log (N/g)) for the input string, where N is
the size of the input string and g the size of the optimal grammar generating
this string. The algorithm works for arbitrary size alphabets, but the running
time is linear assuming that the alphabet Sigma of the input string can be
identified with numbers from 1,ldots, N^c for some constant c. Algorithms with
such an approximation guarantee and running time are known, however all of them
were non-trivial and their analyses were involved. The here presented algorithm
computes the LZ77 factorisation and transforms it in phases to a grammar. In
each phase it maintains an LZ77-like factorisation of the word with at most l
factors as well as additional O(l) letters, where l was the size of the
original LZ77 factorisation. In one phase in a greedy way (by a left-to-right
sweep and a help of the factorisation) we choose a set of pairs of consecutive
letters to be replaced with new symbols, i.e. nonterminals of the constructed
grammar. We choose at least 2/3 of the letters in the word and there are O(l)
many different pairs among them. Hence there are O(log N) phases, each of them
introduces O(l) nonterminals to a grammar. A more precise analysis yields a
bound O(l log(N/l)). As l \leq g, this yields the desired bound O(g log(N/g)).Comment: Accepted for CPM 201
The Spatial String Tension in High Temperature Lattice Gauge Theories
We develop some techniques which allow an analytic evaluation of space-like
observables in high temperature lattice gauge theories. We show that such
variables are described extremely well by dimensional reduction. In particular,
by using results obtained in the context of ``Induced QCD'', we evaluate the
contributions to space-like observables coming from the Higgs sector of the
dimensionally reduced action, we find that they are of higher order in the
coupling constant compared to those coming from the space-like action and hence
neglegible near the continuum limit. In the case of SU(2) gauge theory our
results agree with those obtained through Montecarlo simulations both in (2+1)
and (3+1) dimensions and they also indicate a possible way of removing the gap
between the two values of recently appeared in the literature.Comment: 17 pages, (Latex), DFTT 8/9
Correlation in telomere lengths between feathers and blood cells in pied flycatchers
We are grateful to Toni Laaksonen, Pauliina Teerikorpi, Ville Ojala, Wiebke Schuett, Corinna Adrian and Marie Hardenbicker for their help in the field, and two anonymous reviewers for constructive comments on the manuscript. This research was financially supported by the Turku Collegium for Science and Medicine (grant to AS) and Societas Pro Fauna et Flora Fennica, The Kuopio Naturalists’ Society, and Finnish Cultural Foundation Varsinais-Suomi regional fund (grants to TK). The authors declare to have no conflict of interests. Dataset used in this study will be publicly accessible on Figshare https://figshare.com/s/dffa03e1e91c2e57dc13).Peer reviewedPostprin
Lattice-continuum relations for 3d SU(N)+Higgs theories
3d lattice studies have recently attracted a lot of attention, especially in
connection with finite temperature field theories. One ingredient in these
studies is a perturbative computation of the 2-loop lattice counterterms, which
are exact in the continuum limit. We extend previous such results to SU(N)
gauge theories with Higgs fields in the fundamental and adjoint
representations. The fundamental SU(3)xSU(2) case might be relevant for the
electroweak phase transition in the MSSM, and the adjoint case for the GUT
phase transition and for QCD in the high temperature phase. We also revisit the
standard SU(2)xU(1) and U(1) theories.Comment: 21 page
Testing imaginary vs. real chemical potential in finite-temperature QCD
One suggestion for determining the properties of QCD at finite temperatures
and densities is to carry out lattice simulations with an imaginary chemical
potential whereby no sign problem arises, and to convert the results to real
physical observables only afterwards. We test the practical feasibility of such
an approach for a particular class of physical observables, spatial correlation
lengths in the quark-gluon plasma phase. Simulations with imaginary chemical
potential followed by analytic continuation are compared with simulations with
real chemical potential, which are possible by using a dimensionally reduced
effective action for hot QCD. We find that for imaginary chemical potential the
system undergoes a phase transition at |mu/T| \approx pi/3, and thus
observables are analytic only in a limited range. However, utilising this
range, relevant information can be obtained for the real chemical potential
case.Comment: 14 pages. Some clarifications and references added, figures modified.
To appear in PL
One-variable word equations in linear time
In this paper we consider word equations with one variable (and arbitrary
many appearances of it). A recent technique of recompression, which is
applicable to general word equations, is shown to be suitable also in this
case. While in general case it is non-deterministic, it determinises in case of
one variable and the obtained running time is O(n + #_X log n), where #_X is
the number of appearances of the variable in the equation. This matches the
previously-best algorithm due to D\k{a}browski and Plandowski. Then, using a
couple of heuristics as well as more detailed time analysis the running time is
lowered to O(n) in RAM model. Unfortunately no new properties of solutions are
shown.Comment: submitted to a journal, general overhaul over the previous versio
Faster subsequence recognition in compressed strings
Computation on compressed strings is one of the key approaches to processing
massive data sets. We consider local subsequence recognition problems on
strings compressed by straight-line programs (SLP), which is closely related to
Lempel--Ziv compression. For an SLP-compressed text of length , and an
uncompressed pattern of length , C{\'e}gielski et al. gave an algorithm for
local subsequence recognition running in time . We improve
the running time to . Our algorithm can also be used to
compute the longest common subsequence between a compressed text and an
uncompressed pattern in time ; the same problem with a
compressed pattern is known to be NP-hard
Preliminary heavy-light decay constants from the MILC collaboration
Preliminary results from the MILC collaboration for , , ,
and their ratios are presented. We compute in the quenched
approximation at , 6.0 and 5.7 with Wilson light quarks and static
and Wilson heavy quarks. We attempt to quantify systematic errors due to finite
volume, finite lattice spacing, large , and fitting and extrapolation
uncertainties. The hopping parameter approach of Henty and Kenway is used to
treat the heavy quarks; the sources are Coulomb gauge gaussians.Comment: 3 pages, compressed postscript (uufiles), talk given at Lattice '9
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