A New Finite-lattice study of the Massive Schwinger Model

A new finite lattice calculation of the low lying bound state energies in the massive Schwinger model is presented, using a Hamiltonian lattice formulation. The results are compared with recent analytic series calculations in the low mass limit, and with a new higher order non-relativistic series which we calculate for the high mass limit. The results are generally in good agreement with these series predictions, and also with recent calculations by light cone and related techniques

Density Matrix Renormalisation Group Approach to the Massive Schwinger Model

The massive Schwinger model is studied, using a density matrix renormalisation group approach to the staggered lattice Hamiltonian version of the model. Lattice sizes up to 256 sites are calculated, and the estimates in the continuum limit are almost two orders of magnitude more accurate than previous calculations. Coleman's picture of `half-asymptotic' particles at background field theta = pi is confirmed. The predicted phase transition at finite fermion mass (m/g) is accurately located, and demonstrated to belong in the 2D Ising universality class.Comment: 38 pages, 18 figures, submitted to PR

The association of excitation and inhibition signaling with the relative symptom expression of autism and psychosis-proneness: Implications for psychopharmacology.

The underlying mechanisms of autism and schizophrenia are poorly understood, partly due to a lack of dimension-specific research. Aberrant excitatory and inhibitory neurotransmission are implicated in both conditions, particularly in social dysfunction. This study investigates the extent to which the degree of autistic tendency and psychosis-proneness exclusively and interactively predict excitatory and inhibitory neurotransmitter concentrations in the superior temporal cortex (STC). In 38 adults (18 male, 18-40 years), we obtained autistic tendencies (Autism-Spectrum Quotient [AQ]) and psychosis-proneness scores (Schizotypal Personality Questionnaire [PP]); magnetic resonance spectroscopy (MRS) quantified glutamate and GABA+ concentrations from the STC. Results demonstrated a negative AQ/PP interaction with glutamate concentration for the left STC voxel, where PP increased with glutamate for average AQ, while AQ decreased with glutamate for average-high PP. There was a negative AQ/PP interaction with glutamate/GABA+ ratio for the right STC, AQ increasing with glutamate/GABA+ for low-average PP, while PP decreased with glutamate/GABA+ for high AQ. Consistent with animal studies, we also reveal that overall reduced glutamate/GABA+ ratio might be precipitated by increased right hemisphere GABA+ concentrations. These findings illustrate the importance of considering the concurrent effects of autism and psychosis dimensions on understanding the pathophysiological mechanisms implicated in either condition, and can advance psychopharmacological research into better treatment options for patients

Psychosocial deficits across autism and schizotypal spectra are interactively modulated by excitatory and inhibitory neurotransmission.

Continued human and animal research has strengthened evidence for aberrant excitatory-inhibitory neural processes underlying autism and schizophrenia spectrum disorder psychopathology, particularly psychosocial functioning, in clinical and nonclinical populations. We investigated the extent to which autistic traits and schizotypal dimensions were modulated by the interactive relationship between excitatory glutamate and inhibitory GABA neurotransmitter concentrations in the social processing area of the superior temporal cortex using proton magnetic resonance spectroscopy. In total, 38 non-clinical participants (20 females; age range = 18-35 years, mean (standard deviation) = 23.22 (5.52)) completed the autism spectrum quotient and schizotypal personality questionnaire, and underwent proton magnetic resonance spectroscopy to quantify glutamate and GABA concentrations in the right and left superior temporal cortex. Regression analyses revealed that glutamate and GABA interactively modulated autistic social skills and schizotypal interpersonal features (p <sub>corr</sub> < 0.05), such that those with high right superior temporal cortex glutamate but low GABA concentrations exhibited poorer social and interpersonal skills. These findings evidence an excitation-inhibition imbalance that is specific to psychosocial features across the autism and schizophrenia spectra