Spontaneous symmetry breaking in a two-doublet lattice Higgs model

An SU(2) lattice gauge theory with two doublets of complex scalar fields is considered. All continuous symmetries are identified and, using the nonperturbative methods of lattice field theory, the phase diagram is mapped out by direct numerical simulation. Two-doublet models contain phase transitions that separate qualitatively distinct regions of the parameter space. In some regions global symmetries are spontaneously broken. For some special choices of the model parameters, the symmetry-breaking order parameter is calculated. The pattern of symmetry breaking is verified further through observation of Goldstone bosons.Comment: 24 pages, 13 figures, references added, published versio

Finite Density QCD: a New Approach

We introduce a new approach to analyze the phase diagram of QCD at finite chemical potential and temperature, test it in the Gross-Neveu model at finite baryon density, and apply it to the study of the chemical potential-temperature phase diagram of QCD with four degenerate flavors of Kogut-Susskind type.Comment: 21 pages, 9 figures. Some comments and references adde

Two flavor color superconductivity in nonlocal chiral quark models

We study the competence between chiral symmetry restoration and two flavor color superconductivity (2SC) using a relativistic quark model with covariant nonlocal interactions. We consider two different nonlocal regulators: a Gaussian regulator and a Lorentzian regulator. We find that although the phase diagrams are qualitative similar to those obtained using models with local interactions, in our case the superconducting gaps at medium values of the chemical potential are larger. Consequently, we obtain that in that region the critical temperatures for the disappearance of the 2SC phase might be of the order of 100-120 MeV. We also find that for ratios of the quark-quark and quark-antiquark couplings somewhat above the standard value 3/4, the end point and triple point in the $T-\mu$ phase diagram meet and a phase where both the chiral and diquark condensates are non-negligible appears.Comment: 15 pages incl. 5 Postscript figure

A proper understanding of Millikan

Ruth Millikan’s teleological theory of mental content is complex and often misunderstood. This paper motivates and clarifies some of the complexities of the theory, and shows that paying careful attention to its details yields answers to a number of common objections to teleological theories, in particular, the problem of novel mental states, the problem of functionally false beliefs, and problems about indeterminacy or multiplicity of function

Cognitive Computation sans Representation

The Computational Theory of Mind (CTM) holds that cognitive processes are essentially computational, and hence computation provides the scientific key to explaining mentality. The Representational Theory of Mind (RTM) holds that representational content is the key feature in distinguishing mental from non-mental systems. I argue that there is a deep incompatibility between these two theoretical frameworks, and that the acceptance of CTM provides strong grounds for rejecting RTM. The focal point of the incompatibility is the fact that representational content is extrinsic to formal procedures as such, and the intended interpretation of syntax makes no difference to the execution of an algorithm. So the unique 'content' postulated by RTM is superfluous to the formal procedures of CTM. And once these procedures are implemented in a physical mechanism, it is exclusively the causal properties of the physical mechanism that are responsible for all aspects of the system's behaviour. So once again, postulated content is rendered superfluous. To the extent that semantic content may appear to play a role in behaviour, it must be syntactically encoded within the system, and just as in a standard computational artefact, so too with the human mind/brain - it's pure syntax all the way down to the level of physical implementation. Hence 'content' is at most a convenient meta-level gloss, projected from the outside by human theorists, which itself can play no role in cognitive processing

The QCD phase diagram: A comparison of lattice and hadron resonance gas model calculations

We compare the lattice results on QCD phase diagram for two and three flavors with the hadron resonance gas model (HRGM) calculations. Lines of constant energy density $\epsilon$ have been determined at different baryo-chemical potentials $\mu_B$. For the strangeness chemical potentials $\mu_S$, we use two models. In one model, we explicitly set $\mu_S=0$ for all temperatures and baryo-chemical potentials. This assignment is used in lattice calculations. In the other model, $\mu_S$ is calculated in dependence on $T$ and $\mu_B$ according to the condition of vanishing strangeness. We also derive an analytical expression for the dependence of $T_c$ on $\mu_B/T$ by applying Taylor expansion of $\epsilon$. In both cases, we compare HRGM results on $T_c-\mu_B$ diagram with the lattice calculations. The agreement is excellent, especially when the trigonometric function of $\epsilon$ is truncated up to the same order as done in lattice simulations. For studying the efficiency of the truncated Taylor expansion, we calculate the radius of convergence. For zero- and second-order radii, the agreement with lattice is convincing. Furthermore, we make predictions for QCD phase diagram for non-truncated expressions and physical masses. These predictions are to be confirmed by heavy-ion experiments and future lattice calculations with very small lattice spacing and physical quark masses.Comment: 25 pages, 8 eps figure

Extended brief intervention to address alcohol misuse in people with mild to moderate intellectual disabilities living in the community (EBI-ID): study protocol for a randomised controlled trial.

There is some evidence that people with intellectual disabilities who live in the community are exposed to the same risks of alcohol use as the rest of the population. Various interventions have been evaluated in the general population to tackle hazardous or harmful drinking and alcohol dependence, but the literature evaluating interventions is very limited regarding intellectual disabilities. The National Institute for Health and Clinical Excellence recommends that brief and extended brief interventions be used to help young persons and adults who have screened as positive for hazardous and harmful drinking. The objective of this trial is to investigate the feasibility of adapting and delivering an extended brief intervention (EBI) to persons with mild/moderate intellectual disability who live in the community and whose level of drinking is harmful or hazardous

Infrared Evolution and Phase Structure of a Gauge Theory Containing Different Fermion Representations

We study the evolution of an asymptotically free vectorial SU($N$) gauge theory from the ultraviolet to the infrared and the resultant phase structure in the general case in which the theory contains fermions transforming according to several different representations of the gauge group. We discuss the sequential fermion condensation and dynamical mass generation that occur, and comment on the effect of bare fermion mass terms.Comment: 13 pages, late

EoS of finite density QCD with Wilson fermions by Multi-Parameter Reweighting and Taylor expansion

The equation of state (EoS), quark number density and susceptibility at nonzero quark chemical potential $\mu$ are studied in lattice QCD simulations with a clover-improved Wilson fermion of 2-flavors and RG-improved gauge action. To access nonzero $\mu$, we employ two methods : a multi-parameter reweighting (MPR) in $\mu$ and $\beta$ and Taylor expansion in $\mu/T$. The use of a reduction formula for the Wilson fermion determinant enables to study the reweighting factor in MPR explicitly and heigher-order coefficients in Taylor expansion free from errors of noise method, although calculations are limited to small lattice size. As a consequence, we can study the reliability of the thermodynamical quantities through the consistency of the two methods, each of which has different origin of the application limit. The thermodynamical quantities are obtained from simulations on a $8^3\times 4$ lattice with an intermediate quark mass($m_{\rm PS}/m_{\rm V}=0.8)$. The MPR and Taylor expansion are consistent for the EoS and number density up to $\mu/T\sim 0.8$ and for the number susceptibility up to $\mu/T \sim 0.6$. This implies within a given statistics that the overlap problem for the MPR and truncation error for the Taylor expansion method are negligible in these regions. In order to make MPR methods work, the fluctuation of the reweighting factor should be small. We derive the equation of the reweighting line where the fluctuation is small, and show that the equation of the reweighting line is consistent with the fluctuation minimum condition.Comment: 20 pages, 11 figures. Accepted to JHEP. Discussions are added. Figures for Taylor coefficients (Fig. 7) are modifie

APENet: LQCD clusters a la APE

Developed by the APE group, APENet is a new high speed, low latency, 3-dimensional interconnect architecture optimized for PC clusters running LQCD-like numerical applications. The hardware implementation is based on a single PCI-X 133MHz network interface card hosting six indipendent bi-directional channels with a peak bandwidth of 676 MB/s each direction. We discuss preliminary benchmark results showing exciting performances similar or better than those found in high-end commercial network systems.Comment: Lattice2004(machines), 3 pages, 4 figure