Singularities of Scattering Amplitudes on Unphysical Sheets and Their Interpretation

The analytic structure of two-particle scattering amplitudes on the unphysical sheet of the Riemann surface reached by crossing the two-particle cut is discussed. The singularities of the amplitudes there are shown to be poles and their physical interpretation is studied. The way in which bound states appear on the physical sheet in the Mandelstam representation, both as isolated poles and as cuts, is traced in detail. The properties of partial wave amplitudes and of the full amplitude as a function of energy and angle and of energy and momentum transfer are discussed. Finally, a few remarks are made in connection with unstable states

Equation of state and critical behavior of polymer models: A quantitative comparison between Wertheim's thermodynamic perturbation theory and computer simulations

We present an application of Wertheim's Thermodynamic Perturbation Theory (TPT1) to a simple coarse grained model made of flexibly bonded Lennard-Jones monomers. We use both the Reference Hyper-Netted-Chain (RHNC) and Mean Spherical approximation (MSA) integral equation theories to describe the properties of the reference fluid. The equation of state, the density dependence of the excess chemical potential, and the critical points of the liquid--vapor transition are compared with simulation results and good agreement is found. The RHNC version is somewhat more accurate, while the MSA version has the advantage of being almost analytic. We analyze the scaling behavior of the critical point of chain fluids according to TPT1 and find it to reproduce the mean field exponents: The critical monomer density is predicted to vanish as $n^{-1/2}$ upon increasing the chain length $n$ while the critical temperature is predicted to reach an asymptotic finite temperature that is attained as $n^{-1/2}$. The predicted asymptotic finite critical temperature obtained from the RHNC and MSA versions of TPT1 is found to be in good agreement with the $\Theta$ point of our polymer model as obtained from the temperature dependence of the single chain conformations.Comment: to appear in J.Chem.Phy

Gravitational Wilson Loop in Discrete Quantum Gravity

Results for the gravitational Wilson loop, in particular the area law for large loops in the strong coupling region, and the argument for an effective positive cosmological constant discussed in a previous paper, are extended to other proposed theories of discrete quantum gravity in the strong coupling limit. We argue that the area law is a generic feature of almost all non-perturbative lattice formulations, for sufficiently strong gravitational coupling. The effects on gravitational Wilson loops of the inclusion of various types of light matter coupled to lattice quantum gravity are discussed as well. One finds that significant modifications to the area law can only arise from extremely light matter particles. The paper ends with some general comments on possible physically observable consequences.Comment: 39 pages, 10 figure

Coupling of Gravity to Matter via SO(3,2) Gauge Fields

We consider gravity from the quantum field theory point of view and introduce a natural way of coupling gravity to matter by following the gauge principle for particle interactions. The energy-momentum tensor for the matter fields is shown to be conserved and follows as a consequence of the dynamics in a spontaneously broken SO(3,2) gauge theory of gravity. All known interactions are described by the gauge principle at the microscopic level.Comment: 12 latex page

Electrochemical Evaluation of Stainless Steels in Acidified Sodium Chloride Solutions

This paper presents the results of an investigation in which several 300-series stainless steels (SS): AISI S30403 SS (UNS S30403), AISI 316L SS (UNS S31603), and AISI 317L SS (LINS S31703), as well as highly-alloyed: SS 254-SMO (UNS S32154), AL-6XN (N08367) and AL29-4C (UNS S44735), were evaluated using DC electrochemical techniques in three different electrolyte solutions. The solutions consisted of neutral 3.55% NaCl, 3.55% NaCl in 0.1N HCl, and 3.55% NaCl in 1.0N HCl. These solutions were chosen to simulate environments that are less, similar, and more aggressive, respectively, than the conditions at the Space Shuttle launch pads. The electrochemical test results were compared to atmospheric exposure data and evaluated for their ability to predict the long-term corrosion performance of the subject alloys. The electrochemical measurements for the six alloys indicated that the higher-alloyed SS 254-SMO, AL29-4C, and AL-6XN exhibited significantly higher resistance to localized corrosion than the 300-series SS. There was a correlation between the corrosion performance of the alloys during a two-year atmospheric exposure and the corrosion rates calculated from electrochemical (polarization resistance) measurements

A Relation Between Gravity in (3+1)(3+1)--Dimensions and Pontrjagin Topological Invariant

A relation between the MacDowell-Mansouri theory of gravity and the Pontrjagin toplogical invariant in $(3+1)$ dimensions is discussed. This relation may be of especial interest in the quest of finding a mechanism to go from non-dynamical to dynamical gravity.Comment: 9 pages, Te

Forming new sex partnerships while overseas: findings from the third British national survey of sexual attitudes & lifestyles (Natsal-3)

Objectives: Travelling away from home presents opportunities for new sexual partnerships, which may be associated with sexually transmitted infection (STI) risk. We examined the prevalence of, and factors associated with, reporting new sexual partner(s) while overseas, and whether this differed by partners’ region of residence. Methods: We analysed data from 12 530 men and women aged 16–74 years reporting ≥1 sexual partner(s) in the past 5 years in Britain's third National Survey of Sexual Attitudes and Lifestyles (Natsal-3), a probability survey undertaken 2010–2012. Results: 9.2% (95% CI 8.3% to 10.1%) of men and 5.3% (4.8% to 5.8%) of women reported new sexual partner(s) while overseas in the past 5 years. This was strongly associated with higher partner numbers and other sexual and health risk behaviours. Among those with new partners while overseas, 72% of men and 58% of women reported partner(s) who were not UK residents. Compared with those having only UK partners while abroad, these people were more likely to identify as ‘White Other’ or ‘Non-White’ (vs White British ethnicity), report higher partner numbers, new partners from outside the UK while in the UK and paying for sex (men only) all in the past 5 years. There was no difference in reporting STI diagnosis/es during this time period. Conclusions: Reporting new partners while overseas was associated with a range of sexual risk behaviours. Advice on sexual health should be included as part of holistic health advice for all travellers, regardless of age, destination or reason for travel

Ring diagrams and electroweak phase transition in a magnetic field

Electroweak phase transition in a magnetic field is investigated within the one-loop and ring diagram contributions to the effective potential in the minimal Standard Model. All fundamental fermions and bosons are included with their actual values of masses and the Higgs boson mass is considered in the range $75 GeV \leq m_H \leq 115 GeV$. The effective potential is real at sufficiently high temperature. The important role of fermions and $W$-bosons in symmetry behaviour is observed. It is found that the phase transition for the field strengths $10^{23} - 10^{24}$G is of first order but the baryogenesis condition is not satisfied. The comparison with the hypermagnetic field case is done.Comment: 16 pages, Latex, changed for a mistake in the numerical par

Examples of Embedded Defects (in Particle Physics and Condensed Matter)

We present a series of examples designed to clarify the formalism of the companion paper `Embedded Vortices'. After summarising this formalism in a prescriptive sense, we run through several examples: firstly, deriving the embedded defect spectrum for Weinberg-Salam theory, then discussing several examples designed to illustrate facets of the formalism. We then calculate the embedded defect spectrum for three physical Grand Unified Theories and conclude with a discussion of vortices formed in the superfluid $^3$He-A phase transition.Comment: final corrections. latex fil