Quest for the extra degree of freedom in ƒ <i>(T)</i> gravity

It has recently been shown that f(T) gravity has n(n−3)/2+1 physical degrees of freedom (d.o.f.) in n dimensions, contrary to previous claims. The simplest physical interpretation of this fact is that the theory possesses a scalar d.o.f. This is the case of f(R) gravity, a theory that can be understood in the Einstein frame as general relativity plus a scalaron. The scalar field that represents the extra d.o.f. in f(T) gravity encodes information about the parallelization of the spacetime, which is detected through a reinterpretation of the equations of motion in both the teleparallel Jordan and Einstein frames. The trace of the equations of motion in f(T) gravity shows the propagation of the scalar d.o.f., giving an accurate proof of its existence. We also provide a simple toy model of a physical system with rotational pseudoinvariance, like f(T) gravity, which gives insights into the physical interpretation of the extra d.o.f. We discuss some implications and unusual features of the previously worked out Hamiltonian formalism for f(T) gravity. Finally we show some mathematical tools to implement the Hamiltonian formulation in the Einstein frame of f(T) gravity, which exhibits some problems that should be addressed in future works.Instituto de Física La Plat

Pseudoinvariance and the extra degree of freedom in f (T) gravity

Nonlinear generalizations of teleparallel gravity entail the modification of a Lagrangian that is pseudoinvariant under local Lorentz transformations of the tetrad field. This procedure consequently leads to the loss of the local pseudoinvariance and the appearance of additional degrees of freedom (d.o.f.). The constraint structure of f (T) gravity suggests the existence of one extra d.o.f. when compared with general relativity, which should describe some aspect of the orientation of the tetrad. The purpose of this article is to better understand the nature of this extra d.o.f. by means of a toy model that mimics essential features of f ( T ) gravity. We find that the nonlinear modification of a Lagrangian L possessing a local rotational pseudoinvariance produces two types of solutions. In one case the original gauge-invariant variables—the analogue of the metric in teleparallelism—evolve like when governed by the (nondeformed) Lagrangian L ; these solutions are characterized by a (selectable) constant value of its Lagrangian, which is the manifestation of the extra d.o.f. In the other case, the solutions do contain new dynamics for the original gauge-invariant variables, but the extra d.o.f. does not materialize because the Lagrangian remains invariant on-shell. Coming back to f ( T ) gravity, the first case includes solutions where the torsion scalar T is a constant, to be chosen at the initial conditions (extra d.o.f.), and no new dynamics for the metric is expected. The latter case covers those solutions displaying a genuine modified gravity; T is not a constant, but it is (on-shell) invariant under Lorentz transformations depending only on time. Both kinds of f (T) solutions are exemplified in a flat Friedmann-Lemaître-Robertson-Walker universe. Finally, we present a toy model for a higher-order Lagrangian with rotational invariance [analogous to f (R) gravity] and derive its constraint structure and number of d.o.f.Fil: Ferraro, Rafael. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Física; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; ArgentinaFil: Guzmán Monsalve, María José. Universidad de La Serena; Chil

Quest for the extra degree of freedom in ƒ <i>(T)</i> gravity

It has recently been shown that f(T) gravity has n(n−3)/2+1 physical degrees of freedom (d.o.f.) in n dimensions, contrary to previous claims. The simplest physical interpretation of this fact is that the theory possesses a scalar d.o.f. This is the case of f(R) gravity, a theory that can be understood in the Einstein frame as general relativity plus a scalaron. The scalar field that represents the extra d.o.f. in f(T) gravity encodes information about the parallelization of the spacetime, which is detected through a reinterpretation of the equations of motion in both the teleparallel Jordan and Einstein frames. The trace of the equations of motion in f(T) gravity shows the propagation of the scalar d.o.f., giving an accurate proof of its existence. We also provide a simple toy model of a physical system with rotational pseudoinvariance, like f(T) gravity, which gives insights into the physical interpretation of the extra d.o.f. We discuss some implications and unusual features of the previously worked out Hamiltonian formalism for f(T) gravity. Finally we show some mathematical tools to implement the Hamiltonian formulation in the Einstein frame of f(T) gravity, which exhibits some problems that should be addressed in future works.Instituto de Física La Plat

Quest for the extra degree of freedom in f ( T ) gravity

It has recently been shown that f(T) gravity has n(n−3)/2+1 physical degrees of freedom (d.o.f.) in n dimensions, contrary to previous claims. The simplest physical interpretation of this fact is that the theory possesses a scalar d.o.f. This is the case of f(R) gravity, a theory that can be understood in the Einstein frame as general relativity plus a scalaron. The scalar field that represents the extra d.o.f. in f(T) gravity encodes information about the parallelization of the spacetime, which is detected through a reinterpretation of the equations of motion in both the teleparallel Jordan and Einstein frames. The trace of the equations of motion in f(T) gravity shows the propagation of the scalar d.o.f., giving an accurate proof of its existence. We also provide a simple toy model of a physical system with rotational pseudoinvariance, like f(T) gravity, which gives insights into the physical interpretation of the extra d.o.f. We discuss some implications and unusual features of the previously worked out Hamiltonian formalism for f(T) gravity. Finally we show some mathematical tools to implement the Hamiltonian formulation in the Einstein frame of f(T) gravity, which exhibits some problems that should be addressed in future works.Fil: Ferraro, Rafael. Consejo Nacional de Investigaciónes Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; ArgentinaFil: Guzmán Monsalve, María José. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Física La Plata. Universidad Nacional de La Plata. Facultad de Ciencias Exactas. Instituto de Física La Plata; Argentin

Quest for the extra degree of freedom in ƒ <i>(T)</i> gravity

It has recently been shown that f(T) gravity has n(n−3)/2+1 physical degrees of freedom (d.o.f.) in n dimensions, contrary to previous claims. The simplest physical interpretation of this fact is that the theory possesses a scalar d.o.f. This is the case of f(R) gravity, a theory that can be understood in the Einstein frame as general relativity plus a scalaron. The scalar field that represents the extra d.o.f. in f(T) gravity encodes information about the parallelization of the spacetime, which is detected through a reinterpretation of the equations of motion in both the teleparallel Jordan and Einstein frames. The trace of the equations of motion in f(T) gravity shows the propagation of the scalar d.o.f., giving an accurate proof of its existence. We also provide a simple toy model of a physical system with rotational pseudoinvariance, like f(T) gravity, which gives insights into the physical interpretation of the extra d.o.f. We discuss some implications and unusual features of the previously worked out Hamiltonian formalism for f(T) gravity. Finally we show some mathematical tools to implement the Hamiltonian formulation in the Einstein frame of f(T) gravity, which exhibits some problems that should be addressed in future works.Instituto de Física La Plat

Degrees of freedom in modified teleparallel theories of gravity

Fil: Guzmán Monsalve, María José. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina

Kerr geometry in f(T) gravity

Null tetrads are shown to be a valuable tool in teleparallel theories of modified gravity. We use them to prove that Kerr geometry remains a solution for a wide family of theories of gravity.Fil: Bejarano, Cecilia Soledad. Consejo Nacional de Investigaciónes Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; ArgentinaFil: Ferraro, Rafael. Consejo Nacional de Investigaciónes Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; ArgentinaFil: Guzmán Monsalve, María José. Consejo Nacional de Investigaciónes Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; Argentin

Reflections on the covariance of modified teleparallel theories of gravity

We review the current status of the Lorentz covariance in teleparallel and modified teleparallel theories of gravity, and discuss the controversial features of the different approaches. We also revisit the issue of the remnant Lorentz gauge symmetries in f(T) gravity.Fil: Bejarano, Cecilia Soledad. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; ArgentinaFil: Ferraro, Rafael. Universidad de Buenos Aires. Facultad de Ingeniería. Departamento de Física; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Astronomía y Física del Espacio. - Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Astronomía y Física del Espacio; ArgentinaFil: Fiorini, Franco Luis. Comision Nacional de Energia Atomica. Gerencia D/area Invest y Aplicaciones No Nucleares. Gerencia de Des. Tec. y Proyectos Especiales. Departamento de Ingenieria En Telecomunicaciones.; Argentina. Comisión Nacional de Energía Atómica. Gerencia del Área de Energía Nuclear. Instituto Balseiro; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte; ArgentinaFil: Guzmán Monsalve, María José. Universidad de La Serena; Chile. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Oligomerización de propeno usando como catalizador ZSM-5 modificada con Cr y W

ABSTRACT: In this paper, the composition of ZSM-5 was modified with Cr and W by impregnation, isomorphous substitution and ion exchange, and the resulting catalysts were evaluated in the oligomerization of propene.RESUMEN: En el presente trabajo se modificó la composición de la ZSM-5 con Cr y W por impregnación, sustitución isomórfica e intercambio iónico, y los catalizadores resultantes se evaluaron en la oligomerización de propeno

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