387 research outputs found
Where the electroweak phase transition ends
We give a more precise characterisation of the end of the electroweak phase
transition in the framework of the effective 3d SU(2)--Higgs lattice model than
has been given before. The model has now been simulated at gauge couplings
beta_G=12 and 16 for Higgs masses M_H^*=70, 74, 76 and 80 GeV up to lattices
96^3 and the data have been used for reweighting. The breakdown of finite
volume scaling of the Lee-Yang zeroes indicates the change from a first order
transition to a crossover at lambda_3/g_3^2=0.102(2) in rough agreement with
results of Karsch et al (hep-lat/9608087) at \beta_G=9 and smaller lattices.
The infinite volume extrapolation of the discontinuity Delta
/g_3^2 turns out to be zero at lambda_3/g_3^2=0.107(2) being an upper limit. We
comment on the limitations of the second method.Comment: RevTeX, 19 pages, 11 figures, 2 tables; additional MC-data near the
endpoint considere
Sabotage in Contests: A Survey
A contest is a situation in which individuals expend irretrievable resources to win valuable prize(s). ‘Sabotage’ is a deliberate and costly act of damaging a rival’s' likelihood of winning the contest. Sabotage can be observed in, e.g., sports, war, promotion tournaments, political or marketing campaigns. In this article, we provide a model and various perspectives on such sabotage activities and review the economics literature analyzing the act of sabotage in contests. We discuss the theories and evidence highlighting the means of sabotage, why sabotage occurs, and the effects of sabotage on individual players and on overall welfare, along with possible mechanisms to reduce sabotage. We note that most sabotage activities are aimed at the ablest player, the possibility of sabotage reduces productive effort exerted by the players, and sabotage may lessen the effectiveness of public policies, such as affirmative action, or information revelation in contests. We discuss various policies that a designer may employ to counteract sabotage activities. We conclude by pointing out some areas of future research
The costs of preventing and treating chagas disease in Colombia
Background: The objective of this study is to report the costs of Chagas disease in Colombia, in terms of vector disease control programmes and the costs of providing care to chronic Chagas disease patients with cardiomyopathy.
Methods: Data were collected from Colombia in 2004. A retrospective review of costs for vector control programmes carried out in rural areas included 3,084 houses surveyed for infestation with triatomine bugs and 3,305 houses sprayed with insecticide. A total of 63 patient records from 3 different hospitals were selected for a retrospective review of resource use. Consensus methodology with local experts was used to estimate care seeking behaviour and to complement observed data on utilisation. Findings: The mean cost per house per entomological survey was of 2004), whereas the mean cost of spraying a house with insecticide was 46.4 and 1,028, whereas lifetime costs averaged $11,619 per patient. Chronic Chagas disease patients have limited access to healthcare, with an estimated 22% of patients never seeking care. Conclusion: Chagas disease is a preventable condition that affects mostly poor populations living in rural areas. The mean costs of surveying houses for infestation and spraying infested houses were low in comparison to other studies and in line with treatment costs. Care seeking behaviour and the type of insurance affiliation seem to play a role in the facilities and type of care that patients use, thus raising concerns about equitable access to care. Preventing Chagas disease in Colombia would be cost-effective and could contribute to prevent inequalities in health and healthcare.Wellcome Trus
Hadron spectrum, quark masses and decay constants from light overlap fermions on large lattices
We present results from a simulation of quenched overlap fermions with L\"uscher-Weisz gauge field action on lattices up to and for pion masses down to MeV. Among the quantities we study are the pion, rho and nucleon masses, the light and strange quark masses, and the pion decay constant. The renormalization of the scalar and axial vector currents is done nonperturbatively in the scheme. The simulations are performed at two different lattice spacings, fm and fm, and on two different physical volumes, to test the scaling properties of our action and to study finite volume effects. We compare our results with the predictions of chiral perturbation theory and compute several of its low-energy constants. The pion mass is computed in sectors of fixed topology as well
Structure functions and form factors close to the chiral limit from lattice QCD
Results for nucleon matrix elements (arising from moments of structure
functions) and form factors from a mixture of runs using Wilson, clover and
overlap fermions (both quenched and unquenched) are presented and compared in
an effort to explore the size of the chiral `regime', lattice spacing errors
and quenching artefacts. While no run covers this whole range of effects the
partial results indicate a picture of small lattice spacing errors, small
quenching effects and only reaching the chiral regime at rather light quark
masses.Comment: 7 pages, 7 figures; contribution to the 2003 Workshop on Lattice
Hadron Physics, Cairns, Australia; error in Fig. 4 corrected; minor text
change
Lattice determination of the critical point of QCD at finite T and \mu
Based on universal arguments it is believed that there is a critical point
(E) in QCD on the temperature (T) versus chemical potential (\mu) plane, which
is of extreme importance for heavy-ion experiments. Using finite size scaling
and a recently proposed lattice method to study QCD at finite \mu we determine
the location of E in QCD with n_f=2+1 dynamical staggered quarks with
semi-realistic masses on lattices. Our result is T_E=160 \pm 3.5 MeV
and \mu_E= 725 \pm 35 MeV. For the critical temperature at \mu=0 we obtained
T_c=172 \pm 3 MeV.Comment: misprints corrected, version to appear in JHE
Three loop MSbar operator correlation functions for deep inelastic scattering in the chiral limit
We compute a variety of operator-operator correlation functions to third
order in the MSbar scheme in the chiral limit. These include combinations of
quark bilinear currents with gauge invariant operators such as moments n = 2
and 3 of the flavour non-singlet Wilson operators of deep inelastic scattering
and moment n = 2 of the transversity operator, as well as the correlation
functions of the latter operators with themselves. The explicit values of these
gauge independent correlation functions are required to assist with
non-perturbative matching to lattice regularized calculations of the same
quantities. As part of the computation we determine the mixing matrix of
renormalization constants of these non-singlet currents with their associated
total derivative operators at the same twist to three loops in MSbar. Such
operators are crucial in extracting renormalization constants for the
operator-operator correlation functions which are consistent with the
corresponding renormalization group equation. As a by-product we deduce the
R-ratio for the tensor current to third order in the MSbar scheme.Comment: 38 latex pages, 2 figure
String Breaking in Non-Abelian Gauge Theories with Fundamental Matter Fields
We present clear numerical evidence for string breaking in three-dimensional
SU(2) gauge theory with fundamental bosonic matter through a mixing analysis
between Wilson loops and meson operators representing bound states of a static
source and a dynamical scalar. The breaking scale is calculated in the
continuum limit. In units of the lightest glueball we find . The implications of our results for QCD are discussed.Comment: 4 pages, 2 figures; equations (4)-(6) corrected, numerical results
and conclusions unchange
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