KMS conditions for 4-point Green functions at finite temperature

We study the 4-point function in the Keldysh formalism of the closed time path formulation of real time finite temperature field theory. We derive the KMS conditions for these functions and discuss the number of 4-point functions that are independent. We define a set of `physical' functions which are linear combinations of the usual Keldysh functions. We show that these functions satisfy simple KMS conditions. In addition, we consider a set of integral equations which represent a resummation of ladder graphs. We show that these integral equations decouple when one uses the physical functions that we have defined. We discuss the generalization of these results to QED.Comment: 17 pages in Revtex with 2 figure

QED Electrical Conductivity using the 2PI Effective Action

In this article we calculate the electrical conductivity in QED using the 2PI effective action. We use a modified version of the usual 2PI effective action which is defined with respect to self-consistent solutions of the 2-point functions. We show that the green functions obtained from this modified effective action satisfy ward identities and that the conductivity obtained from the kubo relation is gauge invariant. We work to 3-loop order in the modified 2PI effective action and show explicitly that the resulting expression for the conductivity contains the square of the amplitude that corresponds to all binary collision and production processes.Comment: 24 pages, 21 figure

Ward Identities in Non-equilibrium QED

We verify the QED Ward identity for the two- and three -point functions at non-equilibrium in the HTL limit. We use the Keldysh formalism of real time finite temperature field theory. We obtain an identity of the same form as the Ward identity for a set of one loop self-energy and one loop three-point vertex diagrams which are constructed from HTL effective propagators and vertices.Comment: 19 pages, RevTex, 4 PostScript figures, revised version to be published in Phys. Rev.

Theory of the Resistive Transition in Overdoped Tl2Ba2CuO6+xTl_2Ba_2CuO_{6+x}: Implications for the angular dependence of the quasiparticle scattering rate in High-TcT_c superconductors

We show that recent measurements of the magnetic field dependence of the magnetization, specific heat and resistivity of overdoped $T_c \sim 17K$ $Tl_{2}Ba_{2}CuO_{6+\delta}$ in the vicinity of the superconducting $H_{c2}$ imply that the vortex viscosity is anomalously small and that the material studied is inhomogeneous with small, a few hundred $\AA$, regions in which the local $T_{c}$ is much higher than the bulk $T_{c}$. The anomalously small vortex viscosity can be derived from a microscopic model in which the quasiparticle lifetime varies dramatically around the Fermi surface, being small everywhere except along the zone diagonal (``cold spot''). We propose experimental tests of our results.Comment: 4 pages, LaTex, 2 EPS figure

Transport Theory beyond Binary Collisions

Using the Schwinger-Keldysh technique, we derive the transport equations for a system of quantum scalar fields. We first discuss the general structure of the equations and then their collision terms. Taking into account up to three-loop diagrams in \phi^3 model and up to four-loop diagrams in \phi^4 model, we obtain the transport equations which include the contributions of multi-particle collisions and particle production processes, in addition to mean-field effects and binary interactions.Comment: 30 pages, 21 figures, minor changes, to appear in Phys. Rev.

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

Perceptions Of School By Two Teenage Boys With Asperger Syndrome And Their Mothers: A Qualitative Study

This qualitative study aimed to develop an understanding of the challenges faced by teenage boys with Asperger syndrome and their mothers. A case study approach was used to collect data from two 13-year-old boys who have Asperger syndrome and their mothers in Queensland, Australia. Data were collected through the use of semi¬structured interviews. The words of the boys and their mothers provide a valuable insight into the personal experiences and feelings of the par¬ticipants. An inductive approach to data analysis identified four themes: (1) developmental differences; (2) problems associated with the general characteristics of Asperger syndrome (i.e. communication and social difficulties, restricted range of interests, a need for routine); (3) stress; and (4) 'masquerading'. The first three themes relate strongly to the current literature, but the emergence of masquerading is of particular interest in developing a fuller understanding of the experiences of individuals with Asperger syndrome at school

Perturbative and Nonperturbative Kolmogorov Turbulence in a Gluon Plasma

In numerical simulations of nonabelian plasma instabilities in the hard-loop approximation, a turbulent spectrum has been observed that is characterized by a phase-space density of particles $n(p)\sim p^{-\nu}$ with exponent $\nu\simeq 2$, which is larger than expected from relativistic $2\leftrightarrow 2$ scatterings. Using the approach of Zakharov, L'vov and Falkovich, we analyse possible Kolmogorov coefficients for relativistic $(m \ge 4)$-particle processes, which give at most $\nu=5/3$ perturbatively for an energy cascade. We discuss nonperturbative scenarios which lead to larger values. As an extreme limit we find the result $\nu=5$ generically in an inherently nonperturbative effective field theory situation, which coincides with results obtained by Berges et al.\ in large-$N$ scalar field theory. If we instead assume that scaling behavior is determined by Schwinger-Dyson resummations such that the different scaling of bare and dressed vertices matters, we find that intermediate values are possible. We present one simple scenario which would single out $\nu=2$.Comment: published versio

Studies of anorectal function using high resolution anorectal manometry in health and faecal incontinence

PhDFaecal incontinence (FI) is a prevalent complaint in Western populations and causes significant disability. Impaired motor function of the anal canal is a common pathophysiological feature and assessment of sphincteric function with manometry is a routine part of symptom assessment. High-resolution anorectal manometry (HRAM) may provide a more detailed understanding of anorectal function, however its clinical utility has not been established. Aims The principal aims of this thesis were to: (1) Explore existing practices of anorectal manometry (2) Examine current evidence supporting the use of HRAM (3) Develop and validate a protocol for the performance of HRAM (4) Define normal values for traditional measures of sphincteric function using HRAM (5) Develop and validate novel measures of sphincteric function, and explore whether they improve diagnostic accuracy in patients with FI (6) Examine anorectal function over a prolonged period with HRAM to evaluate the phenomenon of anal sampling (referred to in this thesis as transient anal sphincter relaxations [TASRs]) Methods The following methods were used: (1) A worldwide survey of current practices of anorectal manometry (2) A systemic review of the literature (3) Prospective studies (both standard and prolonged) of anal function in healthy volunteers and patients with FI Results The practice of anorectal manometry is markedly variable internationally with no two centres surveyed employing the same methods. Within the 62 centres surveyed, there were 16 combinations of ways in which squeeze data were reported. A review of the literature demonstrated a growing evidence base for the use of HRAM however there is a paucity of data that confirm added benefits of HRAM over conventional manometry. A standardized protocol for HRAM was developed to allow the reporting of traditional measures of anorectal function. Novel measures derived from HRAM were developed which demonstrate increased sensitivity for the detection of impaired sphincteric control in patients with FI (sensitivity of traditional measure [conventional squeeze increment] 36% vs. 59% for the novel HRAM measure [5-second squeeze profile]). Transient anal sphincter relaxations (TASRs) were characterized using HRAM. In health, TASRs are often perceived by the individual as the urge to pass wind (39% of events) and their frequency increases following meal consumption. Conversely in FI, TASRs are a rare occurrence and are generally not perceived (only one patient (1/10 [10%]) with FI reported GI sensations associated with TASR events). Conclusions Anorectal manometry is in need of standardization. Novel measures derived from HRAM may improve diagnostic utility and further exploration of TASR characteristics might give insight into the pathophysiology of FI.Stefan Galeski fellowship Royal College of Surgeons of Englan