4,031 research outputs found
QCD with light Wilson quarks on fine lattices (II): DD-HMC simulations and data analysis
In this second report on our recent numerical simulations of two-flavour QCD,
we provide further technical details on the simulations and describe the
methods we used to extract the meson masses and decay constants from the
generated ensembles of gauge fields. Among the topics covered are the choice of
the DD-HMC parameters, the issue of stability, autocorrelations and the
statistical error analysis. Extensive data tables are included as well as a
short discussion of the quark-mass dependence in partially quenched QCD,
supplementing the physics analysis that was presented in the first paper in
this series.Comment: TeX source, 35 pages, figures include
On the gauge boson's properties in a candidate technicolor theory
The technicolor scenario replaces the Higgs sector of the standard model with
a strongly interacting sector. One candidate for a realization of such a sector
is two-technicolor Yang-Mills theory coupled to two degenerate flavors of
adjoint, massless techniquarks. Using lattice gauge theory the properties of
the technigluons in this scenario are investigated as a function of the
techniquark mass towards the massless limit. For that purpose the minimal
Landau gauge two-point and three-point correlation functions are determined,
including a detailed systematic error analysis. The results are, within the
relatively large systematic uncertainties, compatible with a behavior very
similar to QCD at finite techniquark mass. However, the limit of massless
techniquarks exhibits features which could be compatible with a
(quasi-)conformal behavior.Comment: 27 pages, 17 figures, 1 table; v2: persistent notational error
corrected, some minor modification
Probabilistic Guarded P Systems, A New Formal Modelling Framework
Multienvironment P systems constitute a general, formal
framework for modelling the dynamics of population biology, which consists
of two main approaches: stochastic and probabilistic. The framework
has been successfully used to model biologic systems at both micro (e.g.
bacteria colony) and macro (e.g. real ecosystems) levels, respectively.
In this paper, we extend the general framework in order to include
a new case study related to P. Oleracea species. The extension is made
by a new variant within the probabilistic approach, called Probabilistic
Guarded P systems (in short, PGP systems). We provide a formal definition,
a simulation algorithm to capture the dynamics, and a survey of
the associated software.Ministerio de Economía y Competitividad TIN2012- 37434Junta de Andalucía P08-TIC-0420
Timing molecular motion and production with a synthetic transcriptional clock
The realization of artificial biochemical reaction networks with unique functionality is one of the main challenges for the development of synthetic biology. Due to the reduced number of components, biochemical circuits constructed in vitro promise to be more amenable to systematic design and quantitative assessment than circuits embedded within living organisms. To make good on that promise, effective methods for composing subsystems into larger systems are needed. Here we used an artificial biochemical oscillator based on in vitro transcription and RNA degradation reactions to drive a variety of “load” processes such as the operation of a DNA-based nanomechanical device (“DNA tweezers”) or the production of a functional RNA molecule (an aptamer for malachite green). We implemented several mechanisms for coupling the load processes to the oscillator circuit and compared them based on how much the load affected the frequency and amplitude of the core oscillator, and how much of the load was effectively driven. Based on heuristic insights and computational modeling, an “insulator circuit” was developed, which strongly reduced the detrimental influence of the load on the oscillator circuit. Understanding how to design effective insulation between biochemical subsystems will be critical for the synthesis of larger and more complex systems
Acute heat stress and dietary methionine effects on IGF-I, GHR, and UCP mRNA expression in liver and muscle of quails.
This study evaluated the expression of insulin-like growth factor I (IGF-I), growth hormone receptor (GHR), and uncoupling protein (UCP) mRNA in muscle and liver of quails that were in thermal comfort or exposed to heat stress and that were fed diets with or without methionine supplementation. Meat quails were fed a diet that either met the nutritional demands for methionine (MS) or did not meet this demand (methionine-deficient diet, MD). The animals were either kept at a thermal comfort temperature (25°C) or exposed to heat stress (38°C for 24 h starting on the 6th day). RNA was extracted from liver and breast muscle, and cDNA was synthesized and amplified using quantitative reverse transcription-polymerase chain reaction. Animals that were fed the MS diet and remained at the thermal comfort temperature exhibited increased IGF-I mRNA expression in the liver (0.56 AU). The GHR mRNA expression in the liver and muscle was influenced by both the study variables. Animals receiving the MS diet showed higher GHR expression, while increased expression was observed in animals at the thermal comfort temperature. The UCP mRNA expression in the muscle was influenced by both methionine supplementation and heat stress. Higher expression was observed in animals that received the MD diet (2.29 vs 3.77 AU) and in animals kept in thermal comfort. Our results suggest that heat stress negatively affects the expression of growth-related genes and that methionine supplementation is necessary to appropriately maintain the levels of IGF-I, GHR, and UCP transcripts for animal metabolism
Early (and Later) LHC Search Strategies for Broad Dimuon Resonances
Resonance searches generally focus on narrow states that would produce a
sharp peak rising over background. Early LHC running will, however, be
sensitive primarily to broad resonances. In this paper we demonstrate that
statistical methods should suffice to find broad resonances and distinguish
them from both background and contact interactions over a large range of
previously unexplored parameter space. We furthermore introduce an angular
measure we call ellipticity, which measures how forward (or backward) the muon
is in eta, and allows for discrimination between models with different parity
violation early in the LHC running. We contrast this with existing angular
observables and demonstrate that ellipticity is superior for discrimination
based on parity violation, while others are better at spin determination.Comment: 31 pages, 19 figures. References added, minor modifications made to
section
Non-resonant leptogenesis in seesaw models with an almost conserved B-L
We review the motivations and some results on leptogenesis in seesaw models
with an almost conserved lepton number. The paper is based on a talk given at
the 5th International Symposium on Symmetries in Subatomic Physics, SSP2012.Comment: 8 pages, 1 figure. Published in the proceedings of the 5th
International Symposium on Symmetries in Subatomic Physics, SSP201
Dynamical R-parity Breaking at the LHC
In a class of extensions of the minimal supersymmetric standard model with
(B-L)/left-right symmetry that explains the neutrino masses, breaking R-parity
symmetry is an essential and dynamical requirement for successful gauge
symmetry breaking. Two consequences of these models are: (i) a new kind of
R-parity breaking interaction that protects proton stability but adds new
contributions to neutrinoless double beta decay and (ii) an upper bound on the
extra gauge and parity symmetry breaking scale which is within the large hadron
collider (LHC) energy range. We point out that an important prediction of such
theories is a potentially large mixing between the right-handed charged lepton
() and the superpartner of the right-handed gauge boson (), which leads to a brand new class of R-parity violating interactions of
type and \widetilde{d^c}^\dagger\u^c
e^c. We analyze the relevant constraints on the sparticle mass spectrum and
the LHC signatures for the case with smuon/stau NLSP and gravitino LSP. We note
the "smoking gun" signals for such models to be lepton flavor/number violating
processes: (or ) and
(or ) without
significant missing energy. The predicted multi-lepton final states and the
flavor structure make the model be distinguishable even in the early running of
the LHC.Comment: 30 pages, 13 figures, 6 tables, reference adde
Top quark tensor couplings
We compute the real and imaginary parts of the one-loop electroweak
contributions to the left and right tensorial anomalous couplings of the
vertex in the Standard Model (SM). For both tensorial couplings we find that
the real part of the electroweak SM correction is close to 10 of the leading
contribution given by the QCD gluon exchange. We also find that the electroweak
real and imaginary parts for the anomalous right coupling are almost of the
same order of magnitude. The one loop SM prediction for the real part of the
left coupling is close to the 3 discovery limit derived from
. Besides, taking into account that the predictions of
new physics interactions are also at the level of a few percents when compared
with the one loop QCD gluon exchange, these electroweak corrections should be
taken into account in order to disentangle new physics effects from the
standard ones. These anomalous tensorial couplings of the top quark will be
investigated at the LHC in the near future where sensitivity to these
contributions may be achieved.Comment: 16 pages, 2 figure
CHY representations for gauge theory and gravity amplitudes with up to three massive particles
We show that a wide class of tree-level scattering amplitudes involving
scalars, gauge bosons, and gravitons, up to three of which may be massive, can
be expressed in terms of a Cachazo-He-Yuan representation as a sum over
solutions of the scattering equations. These amplitudes, when expressed in
terms of the appropriate kinematic invariants, are independent of the masses
and therefore identical to the corresponding massless amplitudes.Comment: 20 pages, 1 figure; v2: minor typos corrected, published versio
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