Observational effects of varying speed of light in quadratic gravity cosmological models

We study different manifestations of the speed of light in theories of gravity where metric and connection are regarded as independent fields. We find that for a generic gravity theory in a frame with locally vanishing affine connection, the usual degeneracy between different manifestations of the speed of light is broken. In particular, the space-time causal structure constant ([Formula: see text]) may become variable in that local frame. For theories of the form [Formula: see text], this variation in [Formula: see text] has an impact on the definition of the luminosity distance (and distance modulus), which can be used to confront the predictions of particular models against Supernovae type Ia (SN Ia) data. We carry out this test for a quadratic gravity model without cosmological constant assuming (i) a constant speed of light and (ii) a varying speed of light (VSL), and find that the latter scenario is favored by the data.

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SNe data analysis in variable speed of light cosmologies without cosmological constant

Modern Physics Letters A ◽

10.1142/s021773231450103x ◽

2014 ◽

Vol 29 (24) ◽

pp. 1450103 ◽

Cited By ~ 4

Author(s):

Pengfei Zhang ◽

Xinhe Meng

Keyword(s):

Dark Energy ◽

Scale Factor ◽

Model Parameters ◽

Type Ia Supernovae ◽

Distance Modulus ◽

Data Sets ◽

Variable Speed ◽

Speed Of Light ◽

Type Ia ◽

Ia Supernovae

In this work, we aim to show the possibilities of the variable speed of light (VSL) theory in explaining the type Ia supernovae (SNe) observations without introducing dark energy. The speed of light is assumed to be scale factor-dependent, which is the most popular assumption in VSL theory. We show the modified calculation of the distance modulus and the validity of the redshift-scale factor relation in VSL theory. Three different models of VSL are tested SNe data-sets with proper constraints on the model parameters. The comparison of the three models and flat ΛCDM in distance modulus is showed. Some basic problems and the difficulties of the confirmation of the VSL theory are also discussed.

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Conformal mapping of the Misner–Sharp mass from gravitational collapse

International Journal of Modern Physics D ◽

10.1142/s0218271816500814 ◽

2016 ◽

Vol 25 (07) ◽

pp. 1650081 ◽

Cited By ~ 9

Author(s):

Fayçal Hammad

Keyword(s):

Conformal Mapping ◽

Gravitational Collapse ◽

Conformal Transformation ◽

Conformal Mappings ◽

Conformal Transformations ◽

Theories Of Gravity ◽

Definition Of ◽

Geometric Definition

The conformal transformation of the Misner–Sharp mass is reexamined. It has recently been found that this mass does not transform like usual masses do under conformal mappings of spacetime. We show that when it comes to conformal transformations, the widely used geometric definition of the Misner–Sharp mass is fundamentally different from the original conception of the latter. Indeed, when working within the full hydrodynamic setup that gave rise to that mass, i.e. the physics of gravitational collapse, the familiar conformal transformation of a usual mass is recovered. The case of scalar–tensor theories of gravity is also examined.

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On the Trigonometric Descriptions of Colors

Applied Physics Research ◽

10.5539/apr.v8n3p5 ◽

2016 ◽

Vol 8 (3) ◽

pp. 5

Author(s):

Jirí Stavek

Keyword(s):

Experimental Data ◽

Transverse Energy ◽

Gravitational Constant ◽

Isaac Newton ◽

Type Ia ◽

New Interpretation ◽

The Stability ◽

Mass Evaporation ◽

Supernovae Type Ia ◽

Insight Into

An attempt is presented for the description of the spectral colors using the standard trigonometric tools in order to extract more information about photons. We have arranged the spectral colors on an arc of the circle with the radius R = 1 and the central angle θ = π/3 when we have defined cos (θ) = λ380/λ760 = 0.5. Several trigonometric operations were applied in order to find the gravity centers for the scotopic, photopic, and mesopic visions. The concept of the center of gravity of colors introduced Isaac Newton. We have postulated properties of the long-lived photons with the new interpretation of the Hubble (Zwicky-Nernst) constant H0 = 2.748… * 10-18 kg kg-1 s-1, the specific mass evaporation rate (SMER) of gravitons from the source mass. The stability of international prototypes of kilogram has been regularly checked. We predict that those standard kilograms due to the evaporation of gravitons lost 8.67 μg kg-1 century-1. The energy of long-lived photons was trigonometrically decomposed into three parts that could be experimentally tested: longitudinal energy, transverse energy and energy of evaporated gravitons. We tested the properties of the long-lived photons with the experimental data published for the best available standard candles: supernovae Type Ia. There was found a surprising match of those experimental data with the model of the long-lived photons. Finally, we have proposed a possible decomposition of the big G (Newtonian gravitational constant) and the small kappa κ (Einsteinian gravitational constant) in order to get a new insight into the mysterious gravitational force and/or the curvature concept.

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SUBLUMINAL OPERA NEUTRINOS

International Journal of Modern Physics A ◽

10.1142/s0217751x12500339 ◽

2012 ◽

Vol 27 (07) ◽

pp. 1250033 ◽

Cited By ~ 2

Author(s):

ICHIRO ODA

Keyword(s):

Special Relativity ◽

Recent Work ◽

Causal Structure ◽

Pion Decay ◽

Speed Of Light ◽

The Earth

The OPERA Collaboration has announced to have observed superluminal neutrinos with a mean energy 17.5 GeV, but afterward the superluminal interpretation of the OPERA results has been refuted theoretically by Cherenkov-like radiation and pion decay. In a recent work, we have proposed a kinematical resolution to this problem. A key idea in our resolution is that the OPERA neutrinos are not superluminal but subluminal since they travel faster than the observed speed of light in vacuum on the earth while they do slower than the true speed of light in vacuum determining the causal structure of events. In this paper, we dwell upon our ideas and present some concrete models, which realize our ideas, based on spin 0, 1 and 2 bosonic fields. We also discuss that the principle of invariant speed of light in special relativity can be replaced with the principle of a universal limiting speed.

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Inflation constraints for classes of f(R) models

International Journal of Geometric Methods in Modern Physics ◽

10.1142/s0219887818502092 ◽

2018 ◽

Vol 15 (12) ◽

pp. 1850209

Author(s):

Joseph Ntahompagaze ◽

Jean Damascène Mbarubucyeye ◽

Shambel Sahlu ◽

Amare Abebe

Keyword(s):

Scalar Field ◽

Early Universe ◽

First Derivative ◽

A Value ◽

Slow Roll ◽

Theories Of Gravity ◽

Text Model ◽

Definition Of ◽

Inflationary Parameters

In this paper, we explore the equivalence between two theories, namely [Formula: see text] and scalar–tensor theories of gravity. We use this equivalence to explore several [Formula: see text] toy models focusing on the inflation epoch of the early universe. The study is done based on the definition of the scalar field in terms of the first derivative of [Formula: see text] model. We have applied the slow-roll approximations during inflationary parameters consideration. The comparison of the numerically computed inflationary parameters with the observations is done. We have inspected that some of the [Formula: see text] models produce numerical values of [Formula: see text] that are in the same range as the suggested values from observations. But for the case of the tensor-to-scalar ratio [Formula: see text], we realized that some of the considered [Formula: see text] models suffer to produce a value which is in agreement with the observed values for different considered space parameter.

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The Hubble constant from eight time-delay galaxy lenses

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa3603 ◽

2020 ◽

Vol 501 (1) ◽

pp. 784-801 ◽

Cited By ~ 2

Author(s):

Philipp Denzel ◽

Jonathan P Coles ◽

Prasenjit Saha ◽

Liliya L R Williams

Keyword(s):

Time Delay ◽

Hubble Constant ◽

Free Form ◽

Microwave Background ◽

Form Analysis ◽

Systematic Uncertainties ◽

Type Ia ◽

Modelling Strategies ◽

Supernovae Type Ia

ABSTRACT We present a determination of the Hubble constant from the joint, free-form analysis of eight strongly, quadruply lensing systems. In the concordance cosmology, we find $H_0{} = 71.8^{+3.9}_{-3.3}\, \mathrm{km}\, \mathrm{s}^{-1}\, \mathrm{Mpc}^{-1}{}{}$ with a precision of $4.97{{\ \rm per\ cent}}$. This is in agreement with the latest measurements from supernovae Type Ia and Planck observations of the cosmic microwave background. Our precision is lower compared to these and other recent time-delay cosmography determinations, because our modelling strategies reflect the systematic uncertainties of lensing degeneracies. We furthermore are able to find reasonable lensed image reconstructions by constraining to either value of H0 from local and early Universe measurements. This leads us to conclude that current lensing constraints on H0 are not strong enough to break the ‘Hubble tension’ problem of cosmology.

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The influence of line opacity treatment in stella on supernova light curves

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa2704 ◽

2020 ◽

Vol 499 (3) ◽

pp. 4312-4324

Author(s):

Alexandra Kozyreva ◽

Luke Shingles ◽

Alexey Mironov ◽

Petr Baklanov ◽

Sergey Blinnikov

Keyword(s):

Radiative Transfer ◽

Spectral Synthesis ◽

Broad Band ◽

Light Curves ◽

Radiation Hydrodynamics ◽

Type Ii ◽

Type Ia ◽

The Impact ◽

Supernovae Type Ia

ABSTRACT We systematically explore the effect of the treatment of line opacity on supernova light curves. We find that it is important to consider line opacity for both scattering and absorption (i.e. thermalization, which mimics the effect of fluorescence). We explore the impact of the degree of thermalization on three major types of supernovae: Type Ia, Type II-peculiar, and Type II-plateau. For this we use the radiative transfer code stella and analyse broad-band light curves in the context of simulations done with the spectral synthesis code artis and in the context of a few examples of observed supernovae of each type. We found that the plausible range for the ratio between absorption and scattering in the radiation hydrodynamics code stella is (0.8–1):(0.2–0), i.e. the recommended thermalization parameter is 0.9.

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The Use of Praesepe for the Definition of the Lower Part of the Zero-Age Main Sequence

Symposium - International Astronomical Union ◽

10.1017/s0074180900145656 ◽

1978 ◽

Vol 80 ◽

pp. 277-280

Author(s):

M. Golay

Keyword(s):

Main Sequence ◽

Absolute Magnitude ◽

Central Star ◽

Distance Modulus ◽

Photometric System ◽

Mass Ratio ◽

Depth Effect ◽

Fitting Procedure ◽

Trigonometric Parallax ◽

Definition Of

In an attempt to determine the Hyades distance (Golay, 1973), it was assumed that stars of the same “photometric 0m.01 box” (see Golay, 1977a) have the same visual absolute magnitude. The large amount of photometric data in the UBV B1B2V1G photometric system allows a discussion on this hypothesis (Golay, 1977b). We have 60 “photometric 0m.01 boxes”, each containing a central star of known trigonometric parallax and at least one Praesepe star. We select the 16 boxes (Table I) containing single stars or binaries with an estimated mass ratio, a relative probable error < 30% for the parallaxes and a standard deviation for colors <0m.007. The UBV B1B2V1G colors, the indices (B-V), (B2-V1) and the magnitude mVare taken from theSecond Catalogue(Rufener, 1976) and the internal catalogue of the Geneva Observatory. The color index (B-V) is taken from Johnson (1952, 1957), Johnson and Knuckles (1955), the trigonometric parallax from Jenkins (1952, 1963) and Gliese (1969) and the spectral type for Hyades stars from Morgan and Hiltner (1965). The listings of all 0m.01 photometric star boxes in the UBV B1B2V1G system are given by Golay (1977c). The parallax obtained for Praesepe is π(0″.001) = 6.175 ± p.e. 0.1, i.e. a distance modulus (m-M) = 6m.05 and a distance of 162 parsecs. Golay (1977c) published the differences of the distance moduli for pairs of clusters having stars in the same box. The distances of these clusters is given in Table III, assuming a distance of 162 pc for Praesepe. The accuracy of this method is independent of both the distance magnitude and the chemical composition of the stars of a cluster since the stars have to be in the same box as a star with a known trigonometric parallax. The main sequence of Praesepe and a sample of Hyades stars, in the same photometric box with a Praesepe star is given in Table II. The depth effect in Praesepe being very small, the main sequence is very thin and the main sequence fitting procedure is better starting from Praesepe than from the Hyades.

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