Two-point functions of chiral fields at one loop in type II

We compute the two-point functions for chiral matter states in toroidal intersecting D6-brane models. In particular, we provide the techniques to calculate Möbius strip diagrams including the worldsheet instanton contribution.     

Supergravity with one auxiliary spinor

We present an “intermediate” off-shell version of N = 1 supergravity and its tensor calculus. The supergravity multiplet has 16 + 16 field components. The formulation can be constrained to either of the minimal ones with 12 + 12 components, or enlarge by matter couplings to several 20 + 20 component versions. Self-coupled to its own axial gauge submultiplet it leads to spontaneous supersymmetry breaking in the form first discussed by Freedman and to a propagating gauge field.     

Minimally doubled fermions at one loop

Minimally doubled fermions have been proposed as a cost-effective realization of chiral symmetry at non-zero lattice spacing. Using lattice perturbation theory at one loop, we study their renormalization properties. Specifically, we investigate the consequences of the breaking of hyper-cubic symmetry, which is a typical feature of this class of fermionic discretizations. Our results for the quark self-energy indicate that the four-momentum undergoes a renormalization which is linearly divergent. We also compute renormalization factors for quark bilinears, construct the conserved vector and axial-vector currents and verify that at one loop the renormalization factors of the latter are equal to one.     

Phenomenological aspects of heterotic orbifold models at one loop

We provide a detailed study of the phenomenology of orbifold compactifications of the heterotic string within the context of supergravity effective theories. Our investigation focuses on those models where the soft Lagrangian is dominated by loop contributions to the various soft supersymmetry breaking parameters. Such models typically predict non-universal soft masses and are thus significantly different from minimal supergravity and other universal models. We consider the pattern of masses that are governed by these soft terms and investigate the implications of certain indirect constraints on supersymmetric models, such as flavor-changing neutral currents, the anomalous magnetic moment of the muon and the density of thermal relic neutralinos. We also comment on the possible discovery of these models at the LHC. These string-motivated models show a novel behavior that interpolates between the phenomenology of unified supergravity models and models dominated by the superconformal anomaly. PACS 11.25.Wx, 12.60.Jv, 04.65.+e     

Ground-state energy of pionic hydrogen to one loop

We investigate the ground-state energy of the atom (pionic hydrogen) in the framework of QCD + QED. In particular, we evaluate the strong energy-level shift. We perform the calculation at next-to-leading order in the low-energy expansion in the framework of the relevant effective field theory. The result provides a relation between the strong energy shift and the pion-nucleon S-wave scattering lengths - evaluated in pure QCD - at next-to-leading order in isospin-breaking and in the low-energy expansion. We compare our result with available model calculations. Received: 11 June 2002 / Published online: 9 October 2002     

New minimal higher derivative supergravity coupled to matter

We consider quadratic invariants in the new minimal formulation of N = 1, 4D supergravity, and obtain a simpler form of the Gauss-Bonnet combination. When added to the Einstein lagrangian, these new multiplets propagate different states than those in the old minimal formulation. In particular, the R + αR² theory is shown to be equivalent to standard supergravity coupled to a massive vector multiplet. Our result shows the non-uniqueness of minimal supersymmetrizations of higher derivative theories.     

Covariant string amplitudes on exotic topologies to one loop

Rules are provided for the calculation of string amplitudes on all exotic topologies to one loop. These topologies include the real projective plane, the disk, the annulus, the Möbius strip, the torus and the Klein bottle. The rules are valid for bosonic strings, superstrings, and heterotic strings either in their critical dimensions or toroidally compactified, and they are applicable to amplitudes with arbitrary external bosonic and fermionic states, including mixed open- and closed-string transitions. The modular invariance of the torus amplitudes is discussed.     

Analytic determination at one loop of the energy-momentum tensor for lattice QCD

We give a completely analytical determination of the corrections to the naive energy-momentum tensor for lattice QCD at one loop. This tensor is conserved and gives rise to the correct trace anomaly.     

The chiral anomaly in supersymmetric gauge theories coupled to supergravity

We extend a previously developed algebraic-cohomological method to calculate an explicit form of the consistent chiral anomaly in a SYM theory coupled to N = 1 supergravity.     

Two loop divergences studied with one loop constrained differential renormalization

In the context of differential renormalization, using constrained differential renormalization rules at one-loop, we show how to obtain concrete results in two-loop calculations without making use of Ward identities. In order to do that, we obtain a list of integrals with overlapping divergences compatible with CDR that can be applied to various two-loop background field calculations. As an example, we obtain the two-loop coefficient of the beta function of QED, SuperQED and Yang–Mills theory.     

Occupation of a resonant level coupled to a chiral Luttinger liquid

We consider a resonant level coupled to a chiral Luttinger liquid which can be realized, e.g., at a fractional quantum Hall edge. We study the dependence of the occupation probability n of the level on its energy epsilon for various values of the Luttinger-liquid parameter g. At g<1/2, a weakly coupled level shows a sharp jump in n(epsilon) at the Fermi level. As the coupling is increased, the magnitude of the jump decreases until sqrt[2g], and then the discontinuity in n(epsilon) disappears. We show that n(epsilon) can be expressed in terms of the magnetization of a Kondo impurity as a function of magnetic field.     

Dilute neutron matter on the lattice at next-to-leading order in chiral effective field theory

We discuss lattice simulations of the ground state of dilute neutron matter at next-to-leading order in chiral effective field theory. In a previous paper the coefficients of the next-to-leading-order lattice action were determined by matching nucleon-nucleon scattering data for momenta up to the pion mass. Here the same lattice action is used to simulate the ground state of up to 12 neutrons in a periodic cube using Monte Carlo simulations. We explore the density range from 2% to 8% of normal nuclear density and analyze the ground-state energy as an expansion about the unitarity limit with corrections due to finite scattering length, effective range, and P -wave interactions.