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G. Amelino-Camelia

Publications and source records attributed to G. Amelino-Camelia.

At least 37 records · Page 2Linked to original sources
arXiv1996

Infra-red fixed point structure characterising SUSY SU(5) symmetry breaking

We analyze the one-loop renormalisation group equations for the parameters of the Higgs potential of a supersymmetric SU(5) model with first step of symmetry breaking involving an adjoint Higgs. In particular, we investigate the running of the parameters that decide the first step of symmetry breaking in an attempt to establish which symmetry-breaking scenarios would be most likely if the model is the effective low-energy description of some more fundamental theory. An infra-red fixed point is identified analytically. We show that it is located at the boundary between the region of Higgs parameter space corresponding to unbroken SU(5) and the region corresponding to the breaking of SU(5) to the Standard Model, and we elaborate on its implications. We also observe that certain forms of the Higgs potential discussed at tree level in the literature are not renormalisation group invariant.

hep-ph↗
arXiv1996

String-Inspired Gravity Coupled to Yang-Mills Fields

String-inspired 1+1-dimensional gravity is coupled to Yang-Mills fields in the Cangemi-Jackiw gauge-theoretical formulation, based on the extended Poincaré group. A family of couplings, which involves metrics obtainable from the physical metric with a conformal rescaling, is considered, and the resulting family of models is investigated both at the classical and the quantum level. In particular, also using a series of Kirillov-Kostant phases, the wave functionals that solve the constraints are identified.

hep-th↗
arXiv1996

Simple GUTs

Together with some positive features, such as the constrained hypercharge assignments, grandunification models typically have some unwelcome aspects, mostly associated with the rich and peculiarly selected matter content. I discuss some ideas which might help to interpret (part of) this apparent complexity arising in grandunification in terms of simple structures. I also point out that the conventional criteria used to establish fine tuning in grandunified models should be modified if these models are viewed as effective low-energy descriptions of a more fundamental theory.

hep-ph↗
arXiv1996

Gravitational Dressing of Aharonov-Bohm Amplitudes

We investigate Aharonov-Bohm scattering in a theory in which charged bosonic matter fields are coupled to topologically massive electrodynamics and topologically massive gravity. We demonstrate that, at one-loop order, the transmuted spins in this theory are related to the ones of ordinary Chern-Simons gauge theory in the same way that the Knizhnik-Polyakov-Zamolodchikov formula relates the Liouville-dressed conformal weights of primary operators to the bare weights in two-dimensional conformal field theories. We remark on the implications of this connection between two-dimensional conformal field theories and three-dimensional gauge and gravity theories for a topological membrane reformulation of strings. We also discuss some features of the gravitational analog of the Aharonov-Bohm effect.

hep-th↗
arXiv1996

Rayleigh-Ritz Variational Approximation and Symmetry Nonrestoration

The investigation of symmetry nonrestoration scenarios has led to a controversy, with certain nonperturbative approximation schemes giving indications in sharp disagreement with those found within conventional perturbation theory. A Rayleigh-Ritz variational approach to the problem, which might be useful in bridging the gap between perturbative and nonperturbative viewpoints, is here proposed. As a first application, this approach is used in the investigation of a $Z_2 \times Z_2$-invariant thermal field theory with two scalar fields, placing particular emphasis on the region of parameter space that has been claimed to support symmetry nonrestoration.

hep-ph↗
arXiv1996

Disoriented Chiral Condensates in Hadron-Hadron Collisions

We review recent progress in the description and understanding of disoriented chiral condensates. Certain important unsolved issues are underlined, and the preliminary results of our program of investigation of these issues in the framework of the classical linear sigma model are reported. We also briefly review a formalism which could be useful at the full non-equilibrium quantum field theory level of analysis.

hep-ph↗
arXiv1996

Comment on Partition Function of Anyon Gas

The general structure of the partition function of an anyon gas is discussed, especially in relation to statements made in Phys. Rev. Lett. 68 (1992) 1621 and Phys. Rev. Lett. 69( 1992) 2877.

hep-th↗
arXiv1996

Calogero-Sutherland Particles as Quasisemions

The ultraviolet structure of the Calogero-Sutherland models is examined, and, in particular, semions result to have special properties. An analogy with ultraviolet structures known in anyon quantum mechanics is drawn, and it is used to suggest possible physical consequences of the observed semionic properties.

hep-th↗
arXiv1996

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.

hep-th↗
arXiv1996

Conformal Dimensions from Topologically Massive Quantum Field Theory

We discuss the evaluation of observables in two-dimensional conformal field theory using the topological membrane description. We show that the spectrum of anomalous dimensions can be obtained perturbatively from the topologically massive quantum field theories by computing radiative corrections to Aharonov-Bohm scattering amplitudes for dynamical charged matter fields. The one-loop corrections in the case of topologically massive Yang-Mills theory are shown to coincide with the scaling dimensions of the induced ordinary and supersymmetric WZNW models. We examine the effects of the dressing of a topologically massive gauge theory by topologically massive gravity and show that the one-loop contributions to the Aharonov-Bohm amplitudes coincide with the leading orders of the KPZ scaling relations for two-dimensional quantum gravity. Some general features of the description of conformal field theories via perturbative techniques in the three-dimensional approach are also discussed.

hep-th↗
arXiv1996

Distance Measurement and Wave Dispersion in a Liouville-String Approach to Quantum Gravity

Within a Liouville approach to non-critical string theory, we discuss space-time foam effects on the propagation of low-energy particles. We find an induced frequency-dependent dispersion in the propagation of a wave packet, and observe that this would affect the outcome of measurements involving low-energy particles as probes. In particular, the maximum possible order of magnitude of the space-time foam effects would give rise to an error in the measurement of distance comparable to that independently obtained in some recent heuristic quantum-gravity analyses. We also briefly compare these error estimates with the precision of astrophysical measurements.

hep-th↗
arXiv1996

On the CJT Formalism in Multi-Field Theories

The issues that arise when using the Cornwall-Jackiw-Tomboulis formalism in multi-field theories are investigated. Particular attention is devoted to the interplay between temperature effects, ultraviolet structure, and the interdependence of the gap equations. Results are presented explicitly in the case of the evaluation of the finite temperature effective potential of a theory with two scalar fields which has attracted interest as a toy model for symmetry nonrestoration at high temperatures. The lowest nontrivial order of approximation of the Cornwall-Jackiw-Tomboulis effective potential is shown to lead to consistent results, which are relevant for recent studies of symmetry nonrestoration by Bimonte and Lozano.

hep-th↗
arXiv1996

On Local Observations in Quantum Gravity

By taking into account both quantum mechanical and general relativistic effects, I derive an equation that describes limitations on the measurability of space-time distances as defined by a material reference system.

gr-qc↗
arXiv1995

Lorentz Anomaly and 1+1-Dimensional Radiating Black Holes

The radiation from the black holes of a 1+1-dimensional chiral quantum gravity model is studied. Most notably, a non-trivial dependence on a renormalization parameter that characterizes the anomaly relations is uncovered in an improved semiclassical approximation scheme; this dependence is not present in the naive semiclassical approximation.

hep-th↗
arXiv1995

Black Hole Radiation (with and) without Weyl Anomaly

In the semiclassical analysis of black hole radiation in matter-coupled dilaton gravity, a one-parameter ``$k$"-family of measures for the path integral quantization of the matter fields is considered. The Weyl anomaly is proportional to the parameter $k$, but the black hole radiation seen by minkowskian observers at future null infinity is $k$-independent.

hep-th↗