First order signatures in 4D pure compact U(1) gauge theory with toroidal and spherical topologies

We study the pure compact U(1) gauge theory with the extended Wilson action (\beta, \gamma couplings) by finite size scaling techniques, in lattices ranging from L=6 to L=24 in the region of \gamma <= 0 with toroidal and spherical topologies. The phase transition presents a double peak structure which survives in the thermodynamical limit in the torus. In the sphere the evidence support the idea of a weaker, but still first order, phase transition. For negative values of gamma the transition becomes weaker and larger lattices are needed to find its asymptotic behaviour. Along the transient region the behaviour is the typical one of a weak first order transition for both topologies, with a region where 1/d < nu < 0.5, which becomes nu compatible with 1/d when larger lattices are used.Comment: Some references added; changes in the text mainly wording. To appear in Phys. Lett.

A f(R) gravity without cosmological constant

In this work we consider the possibility of describing the current evolution of the universe, without the introduction of any cosmological constant or dark energy (DE), by modifying the Einstein-Hilbert (EH) action. In the context of the f(R) gravities within the metric formalism, we show that it is possible to find an action without cosmological constant which exactly reproduces the behavior of the EH action with cosmological constant. In addition the f(R) action is analytical at the origin having Minkowski and Schwarzschild as vacuum solutions. The found f(R) action is highly non-trivial and must be written in terms of hypergeometric functions but, in spite of looking somewhat artificial, it shows that the cosmological constant, or more generally the DE, is not a logical necessity.Comment: 5 pages, no figure

Socioeconomic and bioeconomic performance of Philippine fisheries in the recent decades

The fishing industry in the Philippines was tantamount to a marine capture fishery in the 1950s to 1960s. Aquaculture and inland fishery production were not significant. Only during the 1970s did aquaculture and inland capture fisheries contribute significantly to fish production. From 250 000 t fish production in 1951, this increased substantially to 1.6 million t in the 1990s. An average 4.3% was contributed by fisheries to the gross domestic product from 1988 - 98. Fisheries export earnings reached P12 billion in the 1990s. Exports of fishery products include tuna, shrimps, prawns and seaweed. Fishing industry employees in the Philippines are distributed thus: 70% in the municipal (artisanal) sector, 25% in aquaculture and 5% in the commercial sector. Fish and fish products comprise more than 50% of total animal protein intake vis-α-vis meat and meat products and poultry. However per capita consumption of food fish decreased from 40 kg╖year-1 in 1988 to 36 kg in 1998. In the Philippines, small scale fishing is defined as fishing within municipal waters using fishing vessels of 3 GT or less, or fishing without vessels. In 1948, there were 63 005 fishers rising to 743 544 in 1995. There was a declining trend in catch per unit effort (CPUE) from 2.10 t╖HP-1 in 1948 to 0.29 t╖HP-1 in 1985. Time-series data from 1976 - 87 showed that small pelagics accounted for 38% of total catch followed by demersals, 26%; tuna, 16%; seaweeds, 14%; large pelagics, 6% and invertebrates, 9%. The most important fishing gear in terms of contribution to total catch are gillnets (30%), hook and line (24%) and beach seine (8%). Hook and line accounts for almost 60% of tuna catch while hook and line, gillnets, and fish corrals account for 60% of demersal catch. Commercial fishing can be classified into: (a) small scale commercial fishing (fishing with passive or active gear and utilizing vessels of 3.1 GT up to 20 GT); (b) medium-scale commercial fishing (fishing with active gear and utilizing vessels of 20.1 GT up to 150 GT); and (c) large scale commercial fishing (fishing with active gear and vessels of more than 150 GT). In the 1950s the three dominant types of gear were bag net, the trawl (including beam and otter types) and the round haul seine. The larger tonnage category (more than 100 GT) became more significant in the 1980s. There are 35 species comprising 70 - 95% of total commercial fish production grouped as demersals, small pelagics and large pelagics. Roundscads dominated the small pelagics, followed by slipmouth, a demersal species. Declining catches, disappearance of high value species and increasing volume of juveniles are indications that the fishery is biologically over-fished. This translates as declining profit for the fishery sector. It also means that the fishery employs excess labor and utilizes capital that could be used in other economic sectors.Fishery resources, Fishery surveys, Catch/effort, Trawling, Population characteristics, Biomass, Coastal fisheries, Mathematical models, Marine fisheries, Ecosystems, Socioeconomic aspects, Artisanal fishing, Economic benefits, Fishery industry, Capture fishery economics, ISEW, Philippines,

Study of the Coulomb-Higgs transition in the Abelian Higgs Model

The order of the Coulomb-Higgs transition in the U(1)-Higgs model with unfrozen modulus of the scalar field is studied. Large lattices (up to $24^4$ in one case) and high statistics are used. We fix $\beta =1.15$ and explore specially a region of $\lambda$-values where metastability is observed. We study the thermodynamical limit of several observables, in particular, the latent heat, the specific heat, the decrement of the free energy between the maxima and the central minimum of the two-peaked histogram, the Binder cumulant and the displacement of the critical coupling with the lattice size. The results point towards a second order transition for $\lambda \gtrsim 0.005$, while for smaller values of $\lambda$ the strong metastability growing with the lattice size seems to derive from a first order character.Comment: 10 pages, Latex, epsfig, uuencoded gzipped tar file, 4 figures include

The Coulomb-Higgs transition of the three-parameter U(1)-Higgs model

We find a first order Coulomb--Higgs phase transition at moderately large values of the coupling $\lambda$, and no evidence for a change of order at any finite value of it.Comment: 3 pages, uuencoded compressed ps file. Contribution to Lattice '9