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A. C. Lehum

Publications and source records attributed to A. C. Lehum.

At least 55 records · Page 3Linked to original sources
arXiv2014

Gravitational corrections to the scattering in a massless quantum electrodynamics

We discuss the role of gravitational corrections to the running of the electric charge through the evaluation of scattering amplitudes of charged particles in massless scalar electrodynamics. Computing the complete divergent part of the S-matrix amplitude for two distinct scattering processes, we show that quantum gravitational corrections do not alter the running behavior of the electric charge. Our result does not exclude the possibility that the presence of a second dimensional constant in the model (a cosmological constant or the presence of massive particles) could alter this behavior, as was proposed in earlier works.

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arXiv2014

Noncommutative ${\cal N}=2$ Chern-Simons-matter model

In this work we study the three-dimensional ${\cal N}=2$ supersymmetric Chern-Simons-matter model in a noncommutative space-time. We construct the action of the noncommutative $U(N)$ non-Abelian model in terms of explicit ${\cal N}=2$ supervariables by dimensionally reducing a four-dimensional ${\cal N}=1$ supermultiplet. We also obtain the on-shell ${\cal N}=2$ supersymmetric model writing it in terms of ${\cal N}=1$ superfields. In the noncommutative Abelian case, we show that linear UV divergences are cancelled in Feynman diagrams and logarithmic divergences are absent up to one-loop order, stating that our model is free of UV/IR mixing.

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arXiv2013

Gravitational corrections to the scattering of scalar particles

We evaluated the scattering amplitude of neutral scalar particles at one-loop order in the context of effective field theory of quantum gravity in the presence of a cosmological constant. Our study suggests that quantum gravitational corrections induce an asymptotic freedom behavior to the $λϕ^4$ theory, for a positive cosmological constant. This result hints that a complete theory of quantum gravity can play an important role to avoid the issue of triviality in quantum field theory.

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arXiv2013

Supersymmetry breaking in the three-dimensional nonlinear sigma model

In this work we discuss the phase structure of a deformed supersymmetric nonlinear sigma model in a three-dimensional space-time. The deformation is introduced by a term that breaks supersymmetry explicitly, through imposing a slightly different constraint to the fundamental superfields of the model. Using the tadpole method, we compute the effective potential at leading order in 1/N expansion. From the gap equations, i.e., conditions that minimize the effective potential, we observe that this model presents two phases as the ordinary model, with two remarkable differences: 1) the fundamental fermionic field becomes massive in both phases of the model, which is closely related to the supersymmetry breaking term; 2) the O(N) symmetric phase presents a meta-stable vacuum.

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arXiv2013

Supergauge theories in aether superspace

Within the superfield method we extend the formulation of the Lorentz-breaking aether superspace for supergauge theories, both in three- and in four-dimensional cases.

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arXiv2012

Noncommutative supersymmetric Chern-Simons-matter model

Using the superfield formalism and implementing the canonical noncommutativity, the Kahlerian effective superpotential is evaluated in the three-dimensional noncommutative supersymmetric Chern--Simons-matter model at the two-loop order. The computation of the Kahlerian effective superpotential is enough to determine whether the model can exhibit spontaneous (super) symmetry breaking. It is shown that the model possesses a spontaneous gauge symmetry broken phase, generating masses for the scalar and gauge superfields at the two-loop order. Just as for the commutative version, in the noncommutative case the supersymmetry cannot be broken by radiative corrections via the Coleman-Weinberg mechanism.

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arXiv2011

D=(2+1) O(N) Wess-Zumino model in a large N limit

Using the superfield formalism, the effective Kahlerian superpotential of the massless \cal{N}=1 O(N) Wess-Zumino model is computed in the limit of large N, in three spacetime dimensions. The effective Kahlerian superpotential is evaluated at the subleading order in the 1/N expansion, which involves diagrams up to two-loop order, for a small coupling constant. We show that the O(N) symmetry of the model is preserved in this approximation and that no mass is dynamically generated in the supersymmetric phase. We discuss why spontaneous O(N) symmetry breaking cannot be induced by radiative corrections in such model.

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arXiv2010

Spontaneous breaking of superconformal invariance in (2+1)D supersymmetric Chern-Simons-matter theories in the large N limit

In this work it is studied the spontaneous breaking of superconformal and gauge invariances in the Abelian N=1,2 three-dimensional supersymmetric Chern-Simons-matter theories in a large N limit. It is computed the Kählerian effective superpotential at subleading order and shown that the Coleman-Weinberg mechanism is the responsible for the dynamical generation of a mass scale in the N=1 model. This effect appears due to two-loop diagrams that are logarithmic divergent. In particular, the Coleman-Weinberg mechanism fails when we lift the N=1 to N=2 Supersymmetric Chern-Simons-Matter model, like what happens in a perturbative expansion in the coupling constants.

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arXiv2010

Coleman-Weinberg mechanism in a three-dimensional supersymmetric Chern-Simons-matter model

Using the superfield formalism, we study the dynamical breaking of gauge symmetry in the N=1 three-dimensional supersymmetric Chern-Simons model, coupled to a complex scalar superfield with a quartic self-coupling. This is an analogue of the conformally invariant Coleman-Weinberg model in four spacetime dimensions. We show that a mass for the gauge and matter superfields are dynamically generated after two-loop corrections to the effective superpotential. We also discuss the N=2 extension of our work, showing that the Coleman-Weinberg mechanism in such model is not feasible, because it is incompatible with perturbation theory.

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arXiv2010

A coherent state approach to effective potential in noncommutative D=(2+1) models

In this work we study the effective potential in noncommutative three-dimensional models where the noncommutativity is introduced through the coherent state approach. We discuss some important characteristics that seem to be typical to this approach, specially the behavior of the quantum corrections in the small noncommutativity limit.

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arXiv2009

Equivalence between supersymmetric self-dual and Maxwell-Chern-Simons models coupled to a matter spinor superfield

We study the duality of the supersymmetric self-dual and Maxwell-Chern-Simons theories coupled to a fermionic matter superfield, using a master action. This approach evades the difficulties inherent to the quartic couplings that appear when matter is represented by a scalar superfield. The price is that the spinorial matter superfield represents a unusual supersymmetric multiplet, whose main physical properties we also discuss.

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arXiv2009

Dynamical breaking of gauge symmetry in supersymmetric quantum electrodynamics in three-dimensional spacetime

The dynamical breaking of gauge symmetry in the supersymmetric quantum electrodynamics in three-dimensional spacetime is studied at two-loop approximation. At this level, the effective superpotential is evaluated in a supersymmetric phase. At one-loop order, we observe a generation of the Chern-Simons term due to a parity violating term present in the classical action. At two-loop order, the scalar background superfield acquires a nonvanishing vacuum expectation value, generating a mass term $A^αA_α$ through Coleman-Weinberg mechanism. It is observed that the mass of gauge superfield is predominantly an effect of the topological Chern-Simons term.

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arXiv2008

Dynamical generation of mass in the D=(2+1) Wess-Zumino model

In this work we study the dynamical generation of mass in the massless N=1 Wess-Zumino model in a three dimensional spacetime. Using the tadpole method to compute the effective potential, we observe that supersymmetry is dynamicaly broken together with the discrete symmetry A(x) -> - A(x). We show that this model, differently from non-supersymmetric scalar models, exhibits a consistent perturbative dynamical generation of mass after two loop corrections to the effective potential.

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arXiv2007

Spontaneous gauge symmetry breaking in a supersymmetric Chern-Simons model

This works presents a perturbative analysis of the supersymmetric Chern-Simons model in three spacetime dimensions coupled to a Higgs field, using the superfield formalism. We study the spontaneous symmetry breaking of the U(1) gauge symmetry and evaluate the first quantum corrections to the effective action in the broken phase. We show that the infinite renormalization of the gap equation is enough to ensure the renormalizability of the model at the first loop level.

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