188 research outputs found
Initial Vortex Densities after a Temperature Quench
We calculate the initial density of relativistic global vortices (strings)
produced at a quench and contrast it with the predictions of Kibble and Zurek.Comment: Latex file, 8 pages, No figures. The text contains minor changes that
elucidate the onset of classical behaviour more thoroughly. Also including
the word temperature in the title makes the nature of the transition more
explici
Reconnections of Vortex Loops in the Superfluid Turbulent HeII. Rates of the Breakdown and Fusion processes
Kinetics of merging and breaking down vortex loops is the important part of
the whole vortex tangle dynamics. Another part is the motion of individual
lines, which obeys the Biot-Savart law in presence of friction force and of
applied external velocity fields if any. In the present work we evaluate the
coefficients of the reconnection rates and
. Quantity is a number (per unit of time and per unit of
volume) of events, when two loops with lengths and collide and
form the single loop of length . Quantity
describes the rate of events, when the single loop of the length breaks
down into two the daughter loops of lengths and . These
quantities ave evaluated as the averaged numbers of zeroes of vector
connecting two points on the loops of
and at moment of time . Statistics of the individual
loops is taken from the Gaussian model of vortex tangle. PACS-number 67.40Comment: 9 pages, 5 figures, To be submitted to JLT
Universality and Critical Phenomena in String Defect Statistics
The idea of biased symmetries to avoid or alleviate cosmological problems
caused by the appearance of some topological defects is familiar in the context
of domain walls, where the defect statistics lend themselves naturally to a
percolation theory description, and for cosmic strings, where the proportion of
infinite strings can be varied or disappear entirely depending on the bias in
the symmetry. In this paper we measure the initial configurational statistics
of a network of string defects after a symmetry-breaking phase transition with
initial bias in the symmetry of the ground state. Using an improved algorithm,
which is useful for a more general class of self-interacting walks on an
infinite lattice, we extend the work in \cite{MHKS} to better statistics and a
different ground state manifold, namely , and explore various different
discretisations. Within the statistical errors, the critical exponents of the
Hagedorn transition are found to be quite possibly universal and identical to
the critical exponents of three-dimensional bond or site percolation. This
improves our understanding of the percolation theory description of defect
statistics after a biased phase transition, as proposed in \cite{MHKS}. We also
find strong evidence that the existence of infinite strings in the Vachaspati
Vilenkin algorithm is generic to all (string-bearing) vacuum manifolds, all
discretisations thereof, and all regular three-dimensional lattices.Comment: 62 pages, plain LaTeX, macro mathsymb.sty included, figures included.
also available on
http://starsky.pcss.maps.susx.ac.uk/groups/pt/preprints/96/96011.ps.g
Searching for Signatures of Cosmic Superstrings in the CMB
Because cosmic superstrings generically form junctions and gauge theoretic
strings typically do not, junctions may provide a signature to distinguish
between cosmic superstrings and gauge theoretic cosmic strings. In cosmic
microwave background anisotropy maps, cosmic strings lead to distinctive line
discontinuities. String junctions lead to junctions in these line
discontinuities. In turn, edge detection algorithms such as the Canny algorithm
can be used to search for signatures of strings in anisotropy maps. We apply
the Canny algorithm to simulated maps which contain the effects of cosmic
strings with and without string junctions. The Canny algorithm produces edge
maps. To distinguish between edge maps from string simulations with and without
junctions, we examine the density distribution of edges and pixels crossed by
edges. We find that in string simulations without Gaussian noise (such as
produced by the dominant inflationary fluctuations) our analysis of the output
data from the Canny algorithm can clearly distinguish between simulations with
and without string junctions. In the presence of Gaussian noise at the level
expected from the current bounds on the contribution of cosmic strings to the
total power spectrum of density fluctuations, the distinction between models
with and without junctions is more difficult. However, by carefully analyzing
the data the models can still be differentiated.Comment: 15 page
A tribute to Professor Edward Winter Edward Winter 28 June 1950-18 July 2020
This is an accepted manuscript of an article published by Taylor & Francis in Journal of Sports Sciences on 03/09/2020, available online: https://doi.org/10.1080/02640414.2020.1812283
The accepted version of the publication may differ from the final published version.This tribute honours Professor Edward Winter who, during a distinguished career, made a substantial contribution to the discipline of Sport and Exercise Science. Edward authored more than 200 publications, was involved in the review of more than 2000 manuscripts and abstracts and had extensive experience of supervising and examining research candidates. Specifically here, Professor Winter made a major contribution to the Journal of Sport Sciences as section editor for Sport Performance for over a decade. The editorial Board wishes to formally acknowledge the contribution made by Edward to; the work of the Journal, the development of the British Association of Sport and Exercise Sciences and the science of sport and exercise. This editorial comprises contributions from colleagues across the sport and exercise community that are published elsewhere (Copeland et al., 2020).Published onlin
Information Literacy in Students Entering Higher Education in the French Speaking Community of Belgium: lessons learned from an evaluation
Although universities are providing more and more information literacy training for their undergraduate students, the studentsâ real level of information literacy at the beginning of their studies has never been assessed.
Hence EduDOC has decided to team up with the CIUF âLibraryâ Commission in order to organize a wide study aiming at objectively describing this initial level of information literacy, at identifying the studentsâ main weaknesses, as well as allowing instructors to adjust their training on this basis. The questionnaire was based on a similar study carried out in QuĂ©bec and contains 20 questions grouped in five themes relating to information search steps. It was sent in September 2007 to a random sample of students entering a higher education institution in the French Speaking Community of Belgium for the first time. The studentsâ rather poor results confirm that organizing an information literacy program is imperative if students are to perform well in their studies.Peer reviewe
Renormalization Group Approach to Generalized Cosmological models
We revisit here the problem of generalized cosmology using renormalization
group approach. A complete analysis of these cosmologies, where specific models
appear as asymptotic fixed-points, is given here along with their linearized
stability analysis.Comment: 10 pages, to appear in the International Journal of Theoretical
Physic
Braneworld Dynamics of Inflationary Cosmologies with Exponential Potentials
In this work we consider Randall-Sundrum braneworld type scenarios, in which
the spacetime is described by a five-dimensional manifold with matter fields
confined in a domain wall or three-brane. We present the results of a
systematic analysis, using dynamical systems techniques, of the qualitative
behaviour of Friedmann-Lemaitre-Robertson-Walker type models, whose matter is
described by a scalar field with an exponential potential. We construct the
state spaces for these models and discuss how their structure changes with
respect to the general-relativistic case, in particular, what new critical
points appear and their nature and the occurrence of bifurcation.Comment: 15 pages, 9 figures, RevTex 4. Submitted to Physical Review
Interactions between Cosmic Strings: An Analytical Study
We derive analytic expressions for the interaction energy between two general
cosmic strings as the function of their relative orientation and the
ratio of the coupling constants in the model. The results are relevant to the
statistic description of strings away from critical coupling and shed some
light on the mechanisms involved in string formation and the evolution of
string networks.Comment: 31 pages,REVTEX, Imperial/TP/93-94/3
Complete genome sequence of the Medicago microsymbiont Ensifer (Sinorhizobium) medicae strain WSM419
Ensifer (Sinorhizobium) medicae is an effective nitrogen fixing microsymbiont of a diverse range of annual Medicago (medic) species. Strain WSM419 is an aerobic, motile, non-spore forming, Gram-negative rod isolated from a M. murex root nodule collected in Sardinia, Italy in 1981. WSM419 was manufactured commercially in Australia as an inoculant for annual medics during 1985 to 1993 due to its nitrogen fixation, saprophytic competence and acid tolerance properties. Here we describe the basic features of this organism, together with the complete genome sequence, and annotation. This is the first report of a complete genome se-quence for a microsymbiont of the group of annual medic species adapted to acid soils. We reveal that its genome size is 6,817,576 bp encoding 6,518 protein-coding genes and 81 RNA only encoding genes. The genome contains a chromosome of size 3,781,904 bp and 3 plasmids of size 1,570,951 bp, 1,245,408 bp and 219,313 bp. The smallest plasmid is a fea-ture unique to this medic microsymbiont
- âŠ