scholarly journals Geometries with mismatched branes

2020 ◽  
Vol 2020 (9) ◽  
Author(s):  
Andreas Karch ◽  
Lisa Randall
Keyword(s):  
Boundary Conditions ◽  
Effective Action ◽  
Cosmological Models ◽  
Time Dependent ◽  
De Sitter ◽  
Stabilization Mechanism ◽  
New Class ◽  
Vacuum Solutions ◽  
Single Coordinate

Abstract We study Randall-Sundrum two brane setups with mismatched brane tensions. For the vacuum solutions, boundary conditions demand that the induced metric on each of the branes is either de Sitter, Anti-de Sitter, or Minkowski. For incompatible boundary conditions, the bulk metric is necessarily time-dependent. This introduces a new class of time-dependent solutions with the potential to address cosmological issues and provide alternatives to conventional inflationary (or contracting) scenarios. We take a first step in this paper toward such solutions. One important finding is that the resulting solutions can be very succinctly described in terms of an effective action involving only the induced metric on either one of the branes and the radion field. But the full geometry cannot necessarily be simply described with a single coordinate patch. We concentrate here on the time- dependent solutions but argue that supplemented with a brane stabilization mechanism one can potentially construct interesting cosmological models this way. This is true both with and without a brane stabilization mechanism.

scholarly journals LITTLE RIP COSMOLOGICAL MODELS WITH TIME-DEPENDENT EQUATION OF STATE

2012 ◽  
Vol 27 (36) ◽  
pp. 1250210 ◽  
Author(s):  
I. BREVIK ◽  
V. V. OBUKHOV ◽  
K. E. OSETRIN ◽  
A. V. TIMOSHKIN
Keyword(s):  
Dark Energy ◽  
Equation Of State ◽  
Cosmological Models ◽  
Time Dependent ◽  
De Sitter Spacetime ◽  
De Sitter ◽  
Energy Models ◽  
Sitter Spacetime ◽  
The Universe ◽  
Far Future

Specific dark energy models, leading to the Little Rip (LR) cosmology in the far future, are investigated. Conditions for the occurrence of LR in terms of the parameters present in the proposed equation of state for the dark energy cosmic fluid are studied. Estimates about the time needed before the occurrence of the small singularity in the standard LR model in which the universe approaches the de Sitter spacetime asymptotically, are given.

scholarly journals HOLOGRAPHIC COSMOLOGY IN NON-SUPERSYMMETRIC GRAVITY: THE COSMIC ROLE OF TACHYON IN THE TYPE 0 STRINGS

2007 ◽  
Vol 22 (25n28) ◽  
pp. 2047-2055
Author(s):  
WEN-YU WEN
Keyword(s):  
Effective Action ◽  
Time Dependent ◽  
Tachyon Field ◽  
New Class ◽  
Time Dependent Solution

We present a new class of time-dependent solution to the ten-dimensional type 0 effective action. Given a generic potential of tachyon field, there exist phases where tachyon is either frozen at local extremals or free to propagate along flat directions. In the latter phase, a cosmology model is proposed where the tachyon plays the role of time.

The inverse problem of recovering the coefficients of a differential equations on a graph

2020 ◽  
Vol 28 (5) ◽  
pp. 727-738
Author(s):  
Victor Sadovnichii ◽  
Yaudat Talgatovich Sultanaev ◽  
Azamat Akhtyamov
Keyword(s):  
Inverse Problem ◽  
Inverse Problems ◽  
Differential Equations ◽  
Boundary Value Problem ◽  
Boundary Conditions ◽  
Finite Number ◽  
Characteristic Equation ◽  
Arbitrary Number ◽  
New Class ◽  
Finite Set

AbstractWe consider a new class of inverse problems on the recovery of the coefficients of differential equations from a finite set of eigenvalues of a boundary value problem with unseparated boundary conditions. A finite number of eigenvalues is possible only for problems in which the roots of the characteristic equation are multiple. The article describes solutions to such a problem for equations of the second, third, and fourth orders on a graph with three, four, and five edges. The inverse problem with an arbitrary number of edges is solved similarly.

scholarly journals Blow-up analyses in nonlocal reaction diffusion equations with time-dependent coefficients under Neumann boundary conditions

2020 ◽  
Vol 18 (1) ◽  
pp. 1552-1564
Author(s):  
Huimin Tian ◽  
Lingling Zhang
Keyword(s):  
Boundary Conditions ◽  
Blow Up ◽  
Sufficient Conditions ◽  
Neumann Boundary ◽  
Reaction Diffusion ◽  
Neumann Boundary Conditions ◽  
Reaction Diffusion Equations ◽  
Time Dependent ◽  
Diffusion Equations ◽  
Nonlocal Reaction

Abstract In this paper, the blow-up analyses in nonlocal reaction diffusion equations with time-dependent coefficients are investigated under Neumann boundary conditions. By constructing some suitable auxiliary functions and using differential inequality techniques, we show some sufficient conditions to ensure that the solution u ( x , t ) u(x,t) blows up at a finite time under appropriate measure sense. Furthermore, an upper and a lower bound on blow-up time are derived under some appropriate assumptions. At last, two examples are presented to illustrate the application of our main results.

scholarly journals In Vitro Pharmacodynamics of the New Ketolides HMR 3004 and HMR 3647 (Telithromycin) against Chlamydia pneumoniae

2000 ◽  
Vol 44 (7) ◽  
pp. 1846-1849 ◽  
Author(s):  
I. Gustafsson ◽  
E. Hjelm ◽  
O. Cars
Keyword(s):  
Kinetic Model ◽  
Chlamydia Pneumoniae ◽  
Time Dependent ◽  
Intracellular Pathogen ◽  
Maximal Effect ◽  
Subinhibitory Concentration ◽  
Killing Effect ◽  
New Class ◽  
Unit Reduction

ABSTRACT The ketolides HMR 3004 and HMR 3647 (telithromycin) are a new class of macrolides that have a potential clinical efficacy against intracellular pathogens. The objectives of this study were to investigate the MIC, minimum bactericidal concentration, and time-dependent killing of two Chlamydia pneumoniaestrains of the two ketolides. The killing effect was also studied with a newly developed intracellular in vitro kinetic model. Furthermore, HMR 3647 was studied for the effect of a subinhibitory concentration of 0.5 times the MIC after a preexposure of 10 times the MIC during 12 h. The MICs for both strains were 0.0039 and 0.0156 mg/liter for HMR 3004 and HMR 3647, respectively. Killing with 10 times the MIC was time dependent, increasing from a 1-log-unit decrease in the number of inclusions per well at 48 h to a maximal effect of 2.8-log-unit decrease after 96 h. A preexposure of 10 times the MIC of HMR 3647 for 12 h followed by a subinhibitory concentration of 0.5 times the MIC increased the killing effect to a 1.2-log-unit reduction in inclusions per well. An exposure for 12 h gave poor reduction of inclusions, while a static dose of 10 times the MIC for 72 h showed a 2.2-log-unit reduction in inclusions per well. In the kinetic model, a small number of inclusions were detected after 72 h by one exposure of 10 times the MIC. Regrowth could not be detected after 120 h. The ketolides HMR 3004 and HMR 3647 have bactericidal activity and show a significant sub-MIC effect on the intracellular pathogenC. pneumoniae.

Time-dependent variational principle and the effective action

1979 ◽  
Vol 71 (2-3) ◽  
pp. 158-162 ◽  
Author(s):  
R. Jackiw ◽  
A. Kerman
Keyword(s):  
Variational Principle ◽  
Effective Action ◽  
Time Dependent

scholarly journals FROM p-BRANES TO COSMOLOGY

1999 ◽  
Vol 14 (26) ◽  
pp. 4121-4142 ◽  
Author(s):  
H. LÜ ◽  
S. MUKHERJI ◽  
C. N. POPE
Keyword(s):  
String Theory ◽  
Effective Action ◽  
Dimensional Reduction ◽  
Cosmological Models ◽  
Cosmological Solutions ◽  
M Theory ◽  
The Relationship

We study the relationship between static p-brane solitons and cosmological solutions of string theory or M theory. We discuss two different ways in which extremal p-branes can be generalized to nonextremal ones, and show how wide classes of recently discussed cosmological models can be mapped into nonextremal p-brane solutions of one of these two kinds. We also extend previous discussions of cosmological solutions to include some that make use of cosmological-type terms in the effective action that can arise from the generalized dimensional reduction of string theory or M theory.

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