scholarly journals Missing scalars at the cosmological collider

2021 ◽  
Vol 2021 (12) ◽  
Author(s):  
Qianshu Lu ◽  
Matthew Reece ◽  
Zhong-Zhi Xianyu
Keyword(s):  
Scalar Fields ◽  
Thermal Mass ◽  
De Sitter ◽  
Typically Develop ◽  
Useful Signal ◽  
Light Scalar ◽  
Density Perturbations ◽  
Sitter Background ◽  
Spatially Varying

Abstract Light scalar fields typically develop spatially varying backgrounds during inflation. Very often they do not directly affect the density perturbations, but interact with other fields that do leave nontrivial signals in primordial perturbations. In this sense they become “missing scalars” at the cosmological collider. We study potentially observable signals of these missing scalars, focusing on a special example where a missing scalar distorts the usual oscillatory features in the squeezed bispectrum. The distortion is also a useful signal distinguishing the de Sitter background induced thermal mass from a constant intrinsic mass.

scholarly journals Removing Ostrogradski’s ghost from cosmological perturbations in f(R,Rμν2,Cμνρσ2) gravity

2016 ◽  
Vol 31 (11) ◽  
pp. 1650067 ◽  
Author(s):  
Yuji Akita ◽  
Tsutomu Kobayashi
Keyword(s):  
General Formula ◽  
Ricci Tensor ◽  
Matter Density ◽  
De Sitter ◽  
Cosmological Perturbations ◽  
Text Type ◽  
Cosmological Background ◽  
Density Perturbations ◽  
Sitter Background ◽  
Theories Of Gravity

Recently, it was argued that gravity with the square of the Ricci tensor can be stabilized by adding constraints to the theory in a Lorentz violating way. This was so far demonstrated for fluctuations on the Minkowski/de Sitter background. We show that the same scheme works equally well for removing Ostrogradski’s ghost from fluctuations on a cosmological background in generic [Formula: see text]-type theories of gravity. As an application, we derive the general formula for the spectrum of primordial tensor perturbations from the stabilized theory. The evolution of matter density perturbations is also discussed.

scholarly journals CASIMIR EFFECT FOR A SPHERICAL SHELL IN DE SITTER SPACE–TIME WITH SIGNATURE CHANGE

2008 ◽  
Vol 17 (12) ◽  
pp. 2261-2268
Author(s):  
M. R. SETARE ◽  
F. DARABI
Keyword(s):  
Spherical Shell ◽  
Casimir Effect ◽  
Scalar Fields ◽  
Dirichlet Boundary Conditions ◽  
Massless Scalar ◽  
Late Time ◽  
De Sitter ◽  
Signature Change ◽  
Sitter Background ◽  
Cosmological Constants

We calculate the Casimir stress on a spherical shell in a de Sitter background corresponding to different metric signatures and cosmological constants, for massless scalar fields that satisfy Dirichlet boundary conditions on the shell. We show that a contribution appears due to signature change, which leads to late-time expansion of the bubbles in this background.

ENTROPY OF SCALAR FIELDS IN REISSNER–NORDSTRÖM–(ANTI-)DE SITTER SPACETIMES

1996 ◽  
Vol 11 (25) ◽  
pp. 2027-2036 ◽  
Author(s):  
RONG-GEN CAI ◽  
YUAN-ZHONG ZHANG
Keyword(s):  
Black Holes ◽  
Naked Singularity ◽  
Scalar Fields ◽  
De Sitter Space ◽  
Brick Wall ◽  
De Sitter Spacetime ◽  
Cosmological Horizon ◽  
De Sitter ◽  
Sitter Spacetime ◽  
Sitter Background

The entropy of a free scalar field is calculated in the Reissner–Nordström–(anti-)de Sitter spacetimes. Due to the presence of the cosmological horizon in the Reissner–Nordström–de Sitter spacetime, we introduce a cutoff at the cosmological horizon, besides the cutoff at the horizon of black holes in the brick wall model. The entropy is found to be the sum of two terms, which are proportional to the area of the cosmological horizon and of black hole horizon, respectively. In the Reissner–Nordström–anti-de Sitter spacetime the contribution of the anti-de Sitter background to the entropy of scalar fields vanishes when an infinite volume is taken. The entropy of scalar fields is also evaluated in some special backgrounds described by solutions of Einstein–Maxwell equations with a cosmological constant, such as the cold black holes, lukewarm black holes, ultracold solutions, a naked singularity in de Sitter space, and the de Sitter space. The physical meaning of some results is briefly discussed.

Scalar Fields on Anti-de Sitter Background

2014 ◽  
pp. 53-60
Author(s):  
Gyula Fodor ◽  
Péter Forgács ◽  
Philippe Grandclément
Keyword(s):  
Scalar Fields ◽  
De Sitter ◽  
Sitter Background

scholarly journals CASIMIR STRESS ON PARALLEL PLATES IN DE SITTER SPACE WITH SIGNATURE CHANGE

2007 ◽  
Vol 22 (08n09) ◽  
pp. 1771-1779 ◽  
Author(s):  
M. R. SETARE
Keyword(s):  
Scalar Fields ◽  
Massless Scalar ◽  
Parallel Plates ◽  
False Vacuum ◽  
De Sitter ◽  
Signature Change ◽  
True Vacuum ◽  
Sitter Background ◽  
Robin Boundary ◽  
Cosmological Constants

The Casimir stress on two parallel plates in a de Sitter background corresponding to different metric signatures and cosmological constants is calculated for massless scalar fields satisfying Robin boundary conditions on the plates. Our calculation shows that for the parallel plates with false vacuum between and true vacuum outside, the total Casimir pressure leads to an attraction of the plates at very early universe.

scholarly journals A cosmic microscope for the preheating era

2021 ◽  
Vol 2021 (1) ◽  
Author(s):  
JiJi Fan ◽  
Zhong-Zhi Xianyu
Keyword(s):  
Scalar Field ◽  
Nonlinear Effect ◽  
Large Scale ◽  
Nonlinear Effects ◽  
Light Fields ◽  
Unique Probe ◽  
Light Scalar ◽  
Spatially Varying ◽  
Near Future ◽  
Scalar Perturbations

Abstract Light fields with spatially varying backgrounds can modulate cosmic preheating, and imprint the nonlinear effects of preheating dynamics at tiny scales on large scale fluctuations. This provides us a unique probe into the preheating era which we dub the “cosmic microscope”. We identify a distinctive effect of preheating on scalar perturbations that turns the Gaussian primordial fluctuations of a light scalar field into square waves, like a diode. The effect manifests itself as local non-Gaussianity. We present a model, “modulated partial preheating”, where this nonlinear effect is consistent with current observations and can be reached by near future cosmic probes.

scholarly journals Hawking’s radiation in non-stationary rotating de Sitter background

2011 ◽  
Vol 333 (1) ◽  
pp. 175-185 ◽  
Author(s):  
N. Ibohal ◽  
T. Ibungochouba
Keyword(s):  
De Sitter ◽  
Sitter Background

Dirac particle in electric field with confining scalar potential on (anti)-de Sitter background

2018 ◽  
Vol 33 (34) ◽  
pp. 1850202 ◽  
Author(s):  
N. Messai ◽  
B. Hamil ◽  
A. Hafdallah
Keyword(s):  
Energy Spectrum ◽  
Dirac Equation ◽  
Electric Field ◽  
Scalar Potential ◽  
Dirac Particle ◽  
Wave Functions ◽  
De Sitter ◽  
Sitter Background ◽  
Position Representation

In this paper, we study the (1 + 1)-dimensional Dirac equation in the presence of electric field and scalar linear potentials on (anti)-de Sitter background. Using the position representation, the energy spectrum and the corresponding wave functions are exactly obtained.

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