21,861 research outputs found
Tensor stability in Born-Infeld determinantal gravity
We consider the transverse-traceless tensor perturbation of a spatial flat
homogeneous and isotropic spacetime in Born-Infeld determinantal gravity, and
investigate the evolution of the tensor mode for two solutions in the early
universe. For the first solution where the initial singularity is replaced by a
regular geometric de Sitter inflation of infinite duration, the evolution of
the tensor mode is stable for the parameter spaces ,
and , . For the second solution where the
initial singularity is replaced by a primordial brusque bounce, which suffers a
sudden singularity at the bouncing point, the evolution of the tensor mode is
stable for all regions of the parameter space. Our calculation suggests that
the tensor evolution can hold stability in large parameter spaces, which is a
remarkable property of Born-Infeld determinantal gravity. We also constrain the
theoretical parameter by resorting to
the current bound on the speed of the gravitational waves.Comment: 14 pages, added a general discussion on the tensor stability in Sec.
3, and added Sec. 5 on the parameter constraint, published versio
Quantum phase transition in the one-dimensional period-two and uniform compass model
Quantum phase transition in the one-dimensional period-two and uniform
quantum compass model are studied by using the pseudo-spin transformation
method and the trace map method. The exact solutions are presented, the
fidelity, the nearest-neighbor pseudo-spin entanglement, spin and pseudo-spin
correlation functions are then calculated. At the critical point, the fidelity
and its susceptibility change substantially, the gap of pseudo-spin concurrence
is observed, which scales as (N is system size). The spin correlation
functions show smooth behavior around the critical point. In the period-two
chain, the pseudo-spin correlation functions exhibit a oscillating behavior,
which is absent in the unform chain. The divergent correlation length at the
critical point is demonstrated in the general trend for both cases.Comment: 5 pages, 6 figure
Brane worlds in gravity with auxiliary fields
Recently, Pani, Sotiriou, and Vernieri explored a new theory of gravity by
adding nondynamical fields, i.e., gravity with auxiliary fields [Phys. Rev. D
88, 121502(R) (2013)]. In this gravity theory, higher-order derivatives of
matter fields generically appear in the field equations. In this paper we
extend this theory to any dimensions and discuss the thick braneworld model in
five dimensions. Domain wall solutions are obtained numerically. The stability
of the brane system under the tensor perturbation is analyzed. We find that the
system is stable under the tensor perturbation and the gravity zero mode is
localized on the brane. Therefore, the four-dimensional Newtonian potential can
be realized on the brane.Comment: 7 pages, 4 figure
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