scholarly journals Enlightening the CSL model landscape in inflation

2021 ◽  
Vol 81 (12) ◽  
Author(s):  
Gabriel León ◽  
Gabriel R. Bengochea
Keyword(s):  
Momentum Tensor ◽  
Scale Invariant ◽  
Cosmological Perturbation ◽  
Cosmological Perturbation Theory ◽  
Spacetime Curvature ◽  
Cosmological Context ◽  
Generating Operator ◽  
Spontaneous Localization ◽  
Continuous Spontaneous Localization ◽  
Covariant Version

AbstractWe propose a novel realization for the natural extrapolation of the continuous spontaneous localization (CSL) model, in order to account for the origin of primordial inhomogeneities during inflation. This particular model is based on three main elements: (i) the semiclassical gravity framework, (ii) a collapse-generating operator associated to a relativistic invariant scalar of the energy-momentum tensor, and (iii) an extension of the CSL parameter(s) as a function of the spacetime curvature. Furthermore, employing standard cosmological perturbation theory at linear order, and for a reasonable range within the parameter space of the model, we obtain a nearly scale invariant power spectrum consistent with recent observational CMB data. This opens a vast landscape of different options for the application of the CSL model to the cosmological context, and possibly sheds light on searches for a full covariant version of the CSL theory.

scholarly journals Discussions about the landscape of possibilities for treatments of cosmic inflation involving continuous spontaneous localization models

2020 ◽  
Vol 80 (11) ◽  
Author(s):  
Gabriel R. Bengochea ◽  
Gabriel León ◽  
Philip Pearle ◽  
Daniel Sudarsky
Keyword(s):  
General Nature ◽  
Quantum Field ◽  
Microwave Background ◽  
Cosmic Inflation ◽  
Cosmological Context ◽  
Generating Operator ◽  
General Relativistic ◽  
Spontaneous Localization ◽  
Parameter Values ◽  
Continuous Spontaneous Localization

AbstractIn this work we consider a wide variety of alternatives opened when applying the continuous spontaneous localization (CSL) dynamical collapse theory to the inflationary era. The definitive resolution of many of the issues discussed here will have to await, not only for a general relativistic CSL theory, but for a fully workable theory of quantum gravity. Our concern here is to explore these issues, and to warn against premature conclusions. This exploration includes: two different approaches to deal with quantum field theory and gravitation, the identification of the collapse-generating operator and the general nature and values of the parameters of the CSL theory. All the choices connected with these issues have the potential to dramatically alter the conclusions one can draw. We also argue that the incompatibilities found in a recent paper, between the CSL parameter values and the cosmic microwave background observational data, are associated with specific choices made for the extrapolation to the cosmological context of the CSL theory (as it is known to work in non-relativistic laboratory situations) which do not represent the most natural ones.

HAMILTONIAN GENERAL RELATIVITY IN FINITE SPACE AND COSMOLOGICAL POTENTIAL PERTURBATIONS

2006 ◽  
Vol 21 (28n29) ◽  
pp. 5957-5990 ◽  
Author(s):  
B. M. BARBASHOV ◽  
V. N. PERVUSHIN ◽  
A. F. ZAKHAROV ◽  
V. A. ZINCHUK
Keyword(s):  
General Relativity ◽  
Background Radiation ◽  
Hamiltonian Formulation ◽  
Hamiltonian Reduction ◽  
Specific Reference ◽  
Schwarzschild Solution ◽  
Scale Invariant ◽  
Cosmological Perturbation ◽  
Cosmological Perturbation Theory ◽  
Finite Space

The Hamiltonian formulation of general relativity is considered in finite space–time and a specific reference frame given by the diffeo-invariant components of the Fock simplex in terms of the Dirac–ADM variables. The evolution parameter and energy invariant with respect to the time-coordinate transformations are constructed by the separation of the cosmological scale factor a(x0) and its identification with the spatial averaging of the metric determinant, so that the dimension of the kinemetric group of diffeomorphisms coincides with the dimension of a set of variables whose velocities are removed by the Gauss-type constraints in accordance with the second Nöther theorem. This coincidence allows us to solve the energy constraint, fulfil Dirac's Hamiltonian reduction, and to describe the potential perturbations in terms of the Lichnerowicz scale-invariant variables distinguished by the absence of the time derivatives of the spatial metric determinant. It was shown that the Hamiltonian version of the cosmological perturbation theory acquires attributes of the theory of superfluid liquid, and it leads to a generalization of the Schwarzschild solution. The astrophysical application of this approach to general relativity is considered under supposition that the Dirac–ADM Hamiltonian frame is identified with that of the Cosmic Microwave Background radiation distinguished by its dipole component in the frame of an Earth observer.

scholarly journals Stochastic Gravity and Ontological Quantum Mechanics

2018 ◽  
Author(s):  
Thomas C Andersen
Keyword(s):  
Quantum Mechanics ◽  
Thermal Noise ◽  
Wave Radiation ◽  
Semiclassical Theory ◽  
Noise Component ◽  
Quantum Theories ◽  
Nuclear Systems ◽  
Spontaneous Localization ◽  
Continuous Spontaneous Localization ◽  
Stochastic Gravity

Some physicists surmise that gravity lies outside of quantum mechanics. Thus theories like the standard semiclassical theory of quantum to gravity coupling (that of Rosenfeld and Møller) are possible real models of interaction, rather than a mere approximation of a theory of quantum gravity. Unfortunately, semiclassical gravity creates inconsistencies such as superluminal communication. Alternatives by authors such as Diósi, Martin, Penrose, and Wang often use the term 'stochastic' to set themselves apart from the standard semiclassical theory. These theories couple to fluctuations caused by for instance continuous spontaneous localization, hence the term 'stochastic'. This paper looks at stochastic gravity in the framework of a class of emergent or ontological quantum theories, such as those by Bohm, Cetto, and de Broglie. It is found that much or all of the trouble in connecting gravity with a microscopic system falls away, as Einstein's general relativity is free to react directly with the microscopic beables. The resulting continuous gravitational wave radiation by atomic and nuclear systems does not, in contrast to Einstein's speculation, cause catastrophic problems. The small amount of energy exchanged by gravitational waves may have measurable experimental consequences. A very recent experiment by Vinante et al. performed on a small cantilever at mK temperatures shows a surprising non-thermal noise component, the magnitude of which is consistent with the stochastic gravity coupling explored here.

scholarly journals Maximum turnaround radius in f(R) gravity

2019 ◽  
Vol 28 (03) ◽  
pp. 1950058 ◽  
Author(s):  
Salvatore Capozziello ◽  
Konstantinos F. Dialektopoulos ◽  
Orlando Luongo
Keyword(s):  
Large Scale ◽  
A Priori ◽  
Spherically Symmetric ◽  
Cosmological Perturbation ◽  
Suitable Alternative ◽  
Cosmological Perturbation Theory ◽  
Large Scale Structures ◽  
Scale Structures ◽  
Analytic Expression ◽  
Prescription Rules

The accelerating behavior of cosmic fluid opposes gravitational attraction at present epoch, whereas standard gravity is dominant at small scales. As a consequence, there exists a point where the effects are counterbalanced, dubbed turnaround radius, [Formula: see text]. By construction, it provides a bound on maximum structure sizes of the observed universe. Once an upper bound on [Formula: see text] is provided, i.e. [Formula: see text], one can check whether cosmological models guarantee structure formation. Here, we focus on [Formula: see text] gravity, without imposing a priori the form of [Formula: see text]. We thus provide an analytic expression for the turnaround radius in the framework of [Formula: see text] models. To figure this out, we compute the turnaround radius in two distinct cases: (1) under the hypothesis of static and spherically symmetric spacetime, and (2) by using the cosmological perturbation theory. We thus find a criterion to enable large scale structures to be stable in [Formula: see text] models, circumscribing the class of [Formula: see text] theories as suitable alternative to dark energy. In particular, we get that for constant curvature, the viability condition becomes [Formula: see text], with [Formula: see text] and [Formula: see text], respectively, the observed cosmological constant and the Ricci curvature. This prescription rules out models which do not pass the aforementioned [Formula: see text] limit.

scholarly journals INTRINSIC AMBIGUITY IN SECOND-ORDER VISCOSITY PARAMETERS IN RELATIVISTIC HYDRODYNAMICS

2012 ◽  
Vol 27 (22) ◽  
pp. 1250125 ◽  
Author(s):  
YU NAKAYAMA
Keyword(s):  
Minkowski Space ◽  
Energy Momentum Tensor ◽  
Momentum Tensor ◽  
Space Time ◽  
Second Order ◽  
Relativistic Hydrodynamics ◽  
Conformal Invariant ◽  
Scale Invariant ◽  
Minkowski Space Time

We show that relativistic hydrodynamics in Minkowski space–time has intrinsic ambiguity in second-order viscosity parameters in the Landau–Lifshitz frame. This stems from the possibility of improvements of energy–momentum tensor. There exist at least two viscosity parameters which can be removed by using this ambiguity in scale invariant hydrodynamics in (1+3) dimension, and seemingly nonconformal hydrodynamic theories can be hiddenly conformal invariant.

Delta N Formalism in Cosmological Perturbation Theory

10.1142/10953 ◽  
2018 ◽  
Author(s):  
Ali Akbar Abolhasani ◽  
Hassan Firouzjahi ◽  
Atsushi Naruko ◽  
Misao Sasaki
Keyword(s):  
Perturbation Theory ◽  
Cosmological Perturbation ◽  
Cosmological Perturbation Theory
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