## Publications

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**ABSTRACT:**The constants of motion of a mechanical system with a finite number of degrees of freedom are related to the variational symmetries of a Lagrangian constructed from the Hamiltonian of the original system. The configuration space for this Lagrangian is the phase space of the original system. The symmetries considered in this manner include transformations of the time and may not be canonical in the standard sense.AIP Advances 09/2014; 4(9):097135. DOI:10.1063/1.4896601 · 1.52 Impact Factor -
##### Article: Wavefronts, caustic, ronchigram, and null ronchigrating of a plane wave refracted by an axicon lens

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**ABSTRACT:**The aim of this work is threefold: first we obtain analytical expressions for the wavefront train and the caustic associated with the refraction of a plane wavefront by an axicon lens, second we describe the structure of the ronchigram when the ronchiruling is placed at the flat surface of the axicon and the screen is placed at different relative positions to the caustic region, and third we describe in detail the structure of the null ronchigrating for this system; that is, we obtain the grating such that when it is placed at the flat surface of the axicon its associated pattern, at a given plane perpendicular to the optical axis, is a set of parallel fringes. We find that the caustic has only one branch, which is a segment of a line along the optical axis; the ronchigram exhibits self-intersecting fringes when the screen is placed at the caustic region, and the null ronchigrating exhibits closed loop rulings if we want to obtain its associated pattern at the caustic region.Journal of the Optical Society of America A 02/2014; 31(2):448-59. DOI:10.1364/JOSAA.31.000448 · 1.56 Impact Factor - [Show abstract] [Hide abstract]

**ABSTRACT:**The Plebanski formulation of complex general relativity is given in terms of variables valued in the complexification of the $so(3)$ Lie algebra. Therefore, it is genuinely a gauge theory that is also diffeomorphism-invariant. For this reason, the way that the Levi-Civita connection emerges from this formulation is not direct because both the internal (gauge) and the spacetime connections are geometrical structures a priori not related, there is not a natural link between them. Any possible relationship must be put in by hand or must come from extra hypotheses. In this paper, we analyze the correct relationship between these connections and show how they are related. - [Show abstract] [Hide abstract]

**ABSTRACT:**We perform the coupling of the scalar, Maxwell, and Yang-Mills fields as well as the cosmological constant to BF gravity with Immirzi parameter. The proposed action principles employ auxiliary fields in order to keep a polynomial dependence on the B fields. By handling the equations of motion for the B field and for the auxiliary fields, these latter can be expressed in terms of the physical fields and by substituting these expressions into the original action principles we recover the first-order (Holst) and second-order actions for gravity coupled to the physical matter fields. We consider these results a relevant step towards the understanding of the coupling of matter fields to gravity in the theoretical framework of BF theory.Physical review D: Particles and fields 12/2011; 85(6). DOI:10.1103/PhysRevD.85.064011 · 4.86 Impact Factor - [Show abstract] [Hide abstract]

**ABSTRACT:**A detailed analysis of the BF formulation for general relativity given by Capovilla, Montesinos, Prieto, and Rojas is performed. The action principle of this formulation is written in an equivalent form by doing a transformation of the fields of which the action depends functionally on. The transformed action principle involves two BF terms and the two Lorentz invariants that appear in the original action principle generically. As an application of this formalism, the action principle used by Engle, Pereira, and Rovelli in their spin foam model for gravity is recovered and the coupling of the cosmological constant in such a formulation is obtained.Symmetry Integrability and Geometry Methods and Applications 11/2011; 7. DOI:10.3842/SIGMA.2011.103 · 1.25 Impact Factor - [Show abstract] [Hide abstract]

**ABSTRACT:**The coherent states for a set of quadratic Hamiltonians in the trap regime are constructed. A matrix technique which allows to identify directly the creation and annihilation operators will be presented. Then, the coherent states as simultaneous eigenstates of the annihilation operators will be derived, and they are going to be compared with those attained through the displacement operator method. The corresponding wave function will be found, and a general procedure for obtaining several expected values involving the canonical operators in these states will be described. The results will be illustrated through the asymmetric Penning trap.Journal of Physics A Mathematical and Theoretical 09/2010; 44(3). DOI:10.1088/1751-8113/44/3/035304 · 1.58 Impact Factor - [Show abstract] [Hide abstract]

**ABSTRACT:**The first order Plebanski formulation of (complex) general relativity (GR) in terms of self-dual 2-forms admits a generalization, proposed by Krasnov, that is qualitatively different from other possible generalizations of GR in terms of metric variables. In this paper, we investigate, within a minimal modification, and in a perturbative approach, the geometrical meaning of the field variables used in the Krasnov generalization, and compare them to the field variables used in the Plebanski formulation. Comment: Corrected typosClassical and Quantum Gravity 04/2010; 27(14). DOI:10.1088/0264-9381/27/14/145011 · 3.17 Impact Factor - [Show abstract] [Hide abstract]

**ABSTRACT:**The action principle of the BF type introduced by Capovilla, Montesinos, Prieto, and Rojas (CMPR) which describes general relativity with Immirzi parameter is modified in order to allow the inclusion of the cosmological constant. The resulting action principle is on the same footing as the original Plebanski action in the sense that the equations of motion coming from the new action principle are equivalent to the Holst action principle plus a cosmological constant without the need of imposing additional restrictions on the fields. We consider this result a relevant step towards the coupling of matter fields to gravity in the framework of the CMPR action principle. Comment: 4 pages, no figures, LaTeX filePhysical review D: Particles and fields 02/2010; 81(4). DOI:10.1103/PhysRevD.81.044033 · 4.86 Impact Factor - [Show abstract] [Hide abstract]

**ABSTRACT:**The Husain-Kuchar theory is a four-dimensional background-independent model that has long been viewed as a useful model for addressing several conceptual and technical problems appearing in the quantization of general relativity mainly in the loop quantum gravity approach. The model was defined at Lagrangian level in terms of a su(2)-valued connection one-form $A$ coupled through its curvature to a su(2)-valued one-form field $e$. We address here the problem of writing a Lagrangian formulation for the Husain-Kuchar model as a constrained BF theory motivated by the fact that spin foam models for quantum gravity are related to action principles of the BF type. The Lagrangian action principle for the Husain-Kuchar model reported here differs from a previous one found by Barbero et al in that this description involves a single constrained BF theory rather than two interacting BF theories. It is, essentially, the Plebanski action with the condition on the trace of the Lagrange multipliers removed. Moreover, it can be stated that the relationship between our BF-like action and the original one for the Husain-Kuchar model is the same relationship that exists between the Plebanski action and the self-dual Palatini action for complex general relativity, first because the solution to the constraint on the two-forms $\Sigma^i$ coming from the BF-like action leads to the Husain-Kuchar action, and second because the Hamiltonian analysis of the Husain-Kuchar model is straightforward starting from the BF-like action principle.AIP Conference Proceedings 12/2009; 1196:201. DOI:10.1063/1.3284385 - [Show abstract] [Hide abstract]

**ABSTRACT:**By using a matrix technique, which allows to identify directly the ladder operators, the Penning trap coherent states are derived as eigenstates of the appropriate annihilation operators. These states are compared with the ones obtained through the displacement operator. The associated wave functions and mean values for some relevant operators in these states are also evaluated. It turns out that the Penning trap coherent states minimize the Heisenberg uncertainty relation.Journal of Physics A Mathematical and Theoretical 10/2008; 42(8). DOI:10.1088/1751-8113/42/8/085304 · 1.58 Impact Factor - [Show abstract] [Hide abstract]

**ABSTRACT:**Action principles of the BF type for diffeomorphism invariant topological field theories living in n-dimensional spacetime manifolds are presented. Their construction is inspired by Cuesta and Montesinos' recent paper where Cartan's first and second structure equations together with first and second Bianchi identities are treated as the equations of motion for a field theory. In opposition to that paper, the current approach involves also auxiliary fields and holds for arbitrary n-dimensional space-times. Dirac's canonical analysis for the actions is detailedly carried out in the generic case and it is shown that these action principles define topological field theories, as mentioned. The current formalism is a generic framework to construct geometric theories with local degrees of freedom by introducing addi-tional constraints on the various fields involved that destroy the topological character of the original theory. The latter idea is implemented in two-dimensional spacetimes where gravity coupled to matter fields is constructed out, which has indeed local excitations.Physical review D: Particles and fields 09/2008; 78(6). DOI:10.1103/PhysRevD.78.064046 · 4.86 Impact Factor

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