The 12th annual pharmacogenetics in psychiatry meeting report

The 12th Annual Pharmacogenetics in Psychiatry meeting was held in Hollywood, Florida, from 31 May to 1 June 2013, in conjunction with the NCDEU meeting. It included a series of oral presentations as well as a poster session. This report summarizes the presentations at the conference. (C) 2014 Wolters Kluwer Health vertical bar Lippincott Williams & Wilkins

Non-trivial Infrared Structure in (2+1)-dimensional Quantum Electrodynamics

We show that the gauge-fermion interaction in multiflavour $(2+1)$-dimensional quantum electrodynamics with a finite infrared cut-off is responsible for non-fermi liquid behaviour in the infrared, in the sense of leading to the existence of a non-trivial fixed point at zero momentum, as well as to a significant slowing down of the running of the coupling at intermediate scales as compared with previous analyses on the subject. Both these features constitute deviations from fermi-liquid theory. Our discussion is based on the leading- $1/N$ resummed solution for the wave-function renormalization of the Schwinger-Dyson equations . The present work completes and confirms the expectations of an earlier work by two of the authors (I.J.R.A. and N.E.M.) on the non-trivial infrared structure of the theory.Comment: 10 pages (LaTex), 5 figures (Postscript

Effect of Wavefunction Renormalisation in N-Flavour Qed3 at Finite Temperature

A recent study of dynamical chiral symmetry breaking in N-flavour QED$_3$ at finite temperature is extended to include the effect of fermion wavefunction renormalisation in the Schwinger-Dyson equations. The simple ``zero-frequency'' truncation previously used is found to lead to unphysical results, especially as $T \to 0$. A modified set of equations is proposed, whose solutions behave in a way which is qualitatively similar to the $T=0$ solutions of Pennington et al. [5-8] who have made extensive studies of the effect of wavefunction renormalisation in this context, and who concluded that there was no critical $N_c$ (at T=0) above which chiral symmetry was restored. In contrast, we find that our modified equations predict a critical $N_c$ at $T \not= 0$, and an $N-T$ phase diagram very similar to the earlier study neglecting wavefunction renormalisation. The reason for the difference is traced to the different infrared behaviour of the vacuum polarisation at $T=0$ and at $T \not= 0$.Comment: 17 pages + 13 figures (available upon request), Oxford preprint OUTP-93-30P, IFUNAM preprint FT94-39, LaTe

On the Derivative Expansion at Finite Temperature

In this short note, we indicate the origin of nonanalyticity in the method of derivative expansion at finite temperature and discuss some of its consequences.Comment: 7 pages, UR-1363, ER40685-81

Flow Equations for U_k and Z_k

By considering the gradient expansion for the wilsonian effective action S_k of a single component scalar field theory truncated to the first two terms, the potential U_k and the kinetic term Z_k, I show that the recent claim that different expansion of the fluctuation determinant give rise to different renormalization group equations for Z_k is incorrect. The correct procedure to derive this equation is presented and the set of coupled differential equations for U_k and Z_k is definitely established.Comment: 5 page

Gauge Coupling Instability and Dynamical Mass Generation in N=1 Supersymmetric QED(3)

Using superfield Dyson-Schwinger equations, we compute the infrared dynamics of the semi-amputated full vertex, corresponding to the effective running gauge coupling, in N-flavour {\mathcal N}=1 supersymmetric QED(3). It is shown that the presence of a supersymmetry-preserving mass for the matter multiplet stabilizes the infrared gauge coupling against oscillations present in the massless case, and we therefore infer that the massive vacuum is thus selected at the level of the (quantum) effective action. We further demonstrate that such a mass can indeed be generated dynamically in a self-consistent way by appealing to the superfield Dyson-Schwinger gap equation for the full matter propagator.Comment: 14 pages ReVTeX; four axodraw figures incorporate

Non-linear Dynamics in QED_3 and Non-trivial Infrared Structure

In this work we consider a coupled system of Schwinger-Dyson equations for self-energy and vertex functions in QED_3. Using the concept of a semi-amputated vertex function, we manage to decouple the vertex equation and transform it in the infrared into a non-linear differential equation of Emden-Fowler type. Its solution suggests the following picture: in the absence of infrared cut-offs there is only a trivial infrared fixed-point structure in the theory. However, the presence of masses, for either fermions or photons, changes the situation drastically, leading to a mass-dependent non-trivial infrared fixed point. In this picture a dynamical mass for the fermions is found to be generated consistently. The non-linearity of the equations gives rise to highly non-trivial constraints among the mass and effective (`running') gauge coupling, which impose lower and upper bounds on the latter for dynamical mass generation to occur. Possible implications of this to the theory of high-temperature superconductivity are briefly discussed.Comment: 29 pages LATEX, 7 eps figures incorporated, uses axodraw style. Discussion on the massless case (section 2) modified; no effect on conclusions, typos correcte

On magnetic catalysis in even-flavor QED3

In this paper, we discuss the role of an external magnetic field on the dynamically generated fermion mass in even-flavor QED in three space-time dimensions. Based on some reasonable approximations, we present analytic arguments on the fact that, for weak fields, the magnetically-induced mass increases quadratically with increasing field, while at strong fields one crosses over to a mass scaling logarithmically with the external field. We also confirm this type of scaling behavior through quenched lattice calculations using the non-compact version for the gauge field. Both the zero and finite temperature cases are examined. A preliminary study of the fermion condensate in the presence of magnetic flux tubes on the lattice is also included.Comment: 38 pages latex, 18 figures and a style file (axodraw) incorporated (some clarifying remarks concerning the validity of the approximations made and some references were added correcting an earlier version; no effect on conclusions; version to appear in Phys. Rev. D.

Derivative Expansion and the Effective Action for the Abelian Chern-Simons Theory at Higher Orders

We study systematically the higher order corrections to the parity violating part of the effective action for the Abelian Chern-Simons theory in 2+1 dimensions, using the method of derivative expansion. We explicitly calculate the parity violating parts of the quadratic, cubic and the quartic terms (in fields) of the effective action. We show that each of these actions can be summed, in principle, to all orders in the derivatives. However, such a structure is complicated and not very useful. On the other hand, at every order in the powers of the derivatives, we show that the effective action can also be summed to all orders in the fields. The resulting actions can be expressed in terms of the leading order effective action in the static limit. We prove gauge invariance, both large and small of the resulting effective actions. Various other features of the theory are also brought out.Comment: 36 page