arXiv subjects

Rajendra P. Gupta

Publications and source records attributed to Rajendra P. Gupta.

16 recordsLinked to original sources

arXiv2026

Supernova Time Dilation in Hybrid Expansion-Tired-Light Cosmologies

Dark Energy Survey has shown that the emission light curve widths $Δt_{\rm em}$ of supernovae increase to $Δt_{\rm obs}$, obeying $Δt_{\rm obs}/Δt_{\rm em}=(1+z)^b$ with $b=1.003\pm0.011$, excluding a nondilating redshift. We test hybrid models with $1+z=(1+z_p)(1+z_t)$ and the phenomenological stretch $(1+z_p)R(z)$, where $z_p$ is the redshift associated with the expanding parent universe cosmology, $z_t$ is a tired-light (TL) contribution, and $R$ is the hybrid-to-parent lookback-time ratio. At $z=1$, $R$ and $1+z_t$ differ by $1.3\%$ for CCC+TL and $0.5\%$ for $Λ$CDM+TL, and their 95\% bands overlap the observed relation. This compatibility shows that the observations do not exclude the hybrid models, only fully nonexpanding ones.

physics.gen-ph↗

arXiv2026

Testing Covarying Coupling Constants (CCC) against the full SPARC rotation-curve sample: a like-for-like comparison with MOND and NFW

The Covarying Coupling Constants (CCC) framework, developed to account for high-redshift JWST observations, contains a mechanism -- a covarying-constant effective mass field keyed to local density -- that modifies galactic dynamics without particle dark matter. We test it against the full Spitzer Photometry and Accurate Rotation Curves (SPARC) sample of 175 disc galaxies, extending an earlier study of a few objects. Working in an inverse formulation, in which each model predicts the baryonic rotation curve from the observed one, we compare CCC against Modified Newtonian Dynamics (MOND) and one- and two-parameter Navarro-Frenk-White (NFW) haloes on identical footing, using the reduced $χ^2_ν$. We show that the published sharp density turn-off in the earlier study is unphysical and replace it with a smooth transition -- the density-space analogue of the MOND interpolating function, introducing no new parameter. One-parameter smooth-CCC then performs comparably to galaxy-by-galaxy fitted MOND (the lower $χ^2_ν$ in 56 per cent of galaxies, mean $χ^2_ν$ of 2.58 versus 2.65; the paired difference is not significant), while two-parameter NFW shows a substantially broader fit-quality distribution and a larger tail of poor or boundary-limited fits (mean $χ^2_ν\approx 7$). The CCC turn-off density is not universal (scatter 0.82 dex) and correlates with galaxy size, qualitatively consistent with a spherical reconstruction applied to flattened disc systems. Recast as an acceleration, however, $a_t = V_{\rm flat}^2/R_t$ has scatter 0.33 dex (on the 91-galaxy resolved subset) -- matching the MOND scale $a_0$ (0.34 dex) -- and comparable magnitude of order $2 \times 10^{-10}$ m/s$^2$, with its size correlation removed. Though not designed for galactic dynamics, CCC describes rotation curves as well as galaxy-by-galaxy fitted MOND.

astro-ph.GA↗

arXiv2026

Testing the CCC+TL cosmology with cosmic-chronometer measurements of the Hubble parameter

In a recent paper, it was shown that the Covarying Coupling Constants and Tired Light (CCC+TL) hybrid model yields the Hubble parameter $H(z)$ that is substantially different from its measured value using differential aging of quiescent galaxies as cosmic chronometers (CC). It was claimed that the fit of the CCC+TL model to the $H(z)$ data results in a best-fit value for the parameter $α$, defining the strength of the co-variation of the constants, disagreeing with that for the SN~Ia data at the $\sim 6σ$ level. In this paper we re-examine the assumptions underlying such a comparison. Cosmic-chronometer measurements are designed to be independent of cosmological priors, but they nevertheless rely on stellar population synthesis models, isochrones, and age-dating calibrations developed within standard stellar-evolution physics. Therefore, even before introducing any specific correction factor, the present CC compilation cannot be regarded as a model-independent falsification of CCC+TL without recomputing the relevant stellar population models in that framework. In the absence of such a recalculation, we ask a more limited question: what type and magnitude of modification to the effective differential-age relation would be sufficient to remove the claimed tension? We show that a phenomenological factor of the form $\sim (1+z_t)^{-3}$ with $z_t$ being the TL contribution to the observed redshift, motivated by the scaling of gas cooling times for galaxy formation in the CCC+TL framework compared to $Λ\text{CDM}$, is sufficient to reduce the apparent discrepancy in $α$ to $\sim 0.13σ$. Since $z_t = 0$ for the stellar model primarily developed from local stellar observations, the stellar-aging methods may be unable to verify $\sim (1+z_t)^{-3}$ dependence.

astro-ph.CO↗

arXiv2026

Big Bang Nucleosynthesis Constraints on the CCC+TL Cosmology

We investigate whether Big Bang nucleosynthesis (BBN) remains compatible with the Covarying Coupling Constants plus Tired Light (CCC+TL) cosmology. In this framework, only quantities with explicit length dimensionality covary through a universal scaling function $f \left( z \right)$, while dimensionless constants and dimensionless ratios remain invariant. At the redshifts $z$ relevant to BBN, $f \left( z \right )$ approaches a constant plateau $f_{\text{max}} \left( z \right) \simeq 3$, and the tired-light contribution is negligible, so the early-time dynamics reduce to a global rescaling of dimensioned quantities. In particular, the Hubble expansion rate $H$ at fixed temperature $T$ satisfies $H_{\text{CTL}} \left( T \right) = f^{-1}_{\text{max}} H_{Λ\text{CDM}}\left( T\right)$, implying a longer cooling time $Δt$ between weak freeze-out and the onset of nucleosynthesis by the same factor (CCC+TL labeled as $\textit{CTL}$). We find that BBN predictions are preserved provided the relevant interaction rates $Γ$ and decay rates governing the neutron lifetime $τ_n$ share the same plateau scaling as $H$, so that governing combinations such as $Γ\text{/}H$ and $\text{exp} \left( -Δt \text{/} τ_n \right)$ remain invariant. Implementing these plateau rescalings in the Kawano/NUC123 network (via a single control parameter $\texttt{fctl} \equiv f_{\text{max}}$) yields identical light-element abundances for $\texttt{fctl}= 1$ ($Λ$CDM) and $\texttt{fctl} = 3\left( \text{CCC+TL} \right)$ to within $10^{-3} - 10^{-4}$ level, consistent with numerical rounding. We also illustrate that adopting the lower late-time CCC+TL baryon density from the Pantheon+ data fit can reduce the ${}^7\text{Li}$ discrepancy but simultaneously increases D/H, implying that BBN alone does not select between the late-time baryon-density inferences considered here.

astro-ph.CO↗

arXiv2025

Evolution of Size, Mass, and Density of Galaxies Since Cosmic Dawn

The formation and evolution of galaxies and other astrophysical objects have become of great interest, especially since the launch of the James Webb Space Telescope in 2021. The mass, size, and density of objects in the early universe appear to be drastically different from those predicted by the standard cosmology - the $Λ$CDM model. This work shows that the mass-size-density evolution is not surprising when we use the CCC+TL cosmology, which is based on the concepts of covarying coupling constants in an expanding universe and the tired light effect contributing to the observed redshift. This model is consistent with supernovae Pantheon+ data, the angular size of the cosmic dawn galaxies, BAO, CMB sound horizon, galaxy formation time scales, time dilation, galaxy rotation curves, etc., and does not have the coincidence problem. The effective radii $r_e$ of the objects are larger in the new model by $r_e \propto (1+z)^{0.93}$. Thus, the object size evolution in different studies, estimated as $r_e \propto (1+z)^s$ with $s=-1.0 \pm {0.3}$, is modified to $r_e \propto (1+z)^{s+0.93}$, the dynamical mass by $(1+z)^{0.93}$, and number density by $(1+z)^{-2.80}$. The luminosity modification increases slowly with $z$ to 1.8 at $z=20$. Thus, the stellar mass increase is modest, and the luminosity and stellar density decrease are mainly due to the larger object size in the new model. Since the aging of the universe is stretched in the new model, its temporal evolution is much slower (e.g., at $z=10$, the age is about a dex longer); stars, black holes, and galaxies do not have to form at unrealistic rates.

physics.gen-ph↗

arXiv2025

Testing CCC+TL Cosmology with Galaxy Rotation Curves

This paper aims to explore whether astrophysical observations, primarily galaxy rotation curves, result from covarying coupling constants (CCC) rather than from dark matter. We have shown in earlier papers that cosmological observations, such as supernovae type 1a (Pantheon+), the small size of galaxies at cosmic dawn, baryon acoustic oscillations (BAO), the sound horizon in the cosmic microwave background (CMB), and time dilation effect, can be easily accounted for without requiring dark energy and dark matter when coupling constants are permitted to evolve in an expanding Universe, as predicted by Dirac, and the redshift is considered jointly due to the Universe's expansion and Zwicky's tired light (TL) effect. Here, we show that the CCC parameter α is responsible for generating the illusion of dark matter and dark energy, which we call α-matter and α-energy, and is influenced by the baryonic matter density distribution. While cosmologically α is a constant determined for the homogenous and isotropic Universe, e.g., by fitting Pantheon+ data, it can vary locally due to the extreme anisotropy of the matter distribution. Thus, in high baryonic density regions, one expects α-matter and α-energy densities to be relatively low and vice versa. We present its application to a few galaxy rotation curves from the SPARC database and find the results promising.

astro-ph.CO↗

arXiv2024

Measuring inertial mass with Kibble balance

A Kibble balance measures the $gravitational$ mass (weight) of a test mass with extreme precision by balancing the gravitational pull on the test mass against the electromagnetic lift force. The uncertainty in such mass measurement is currently ~$1\times 10^{-8} $. We show how the same Kibble balance can be used to measure the $inertial$ mass of a test mass, that too with potentially 50% better measurement uncertainty, i.e., ~$5\times 10^{-9} $. For measuring the inertial mass, the weight of the test mass and the assembly holding it is precisely balanced by a counterweight. The application of the known electromagnetic force accelerates the test mass. Measuring the velocity after a controlled elapsed time provides the acceleration and, consequently, the inertial mass of the accelerated assembly comprising the Kibble balance coil and the mass holding pan. Repeating the measurement with the test mass added to the assembly and taking the difference between the two measurements yields the inertial mass of the test mass. Thus, the extreme precision inertial and gravitational mass measurement of a test mass with a Kibble balance could provide a test of the equivalence principle. We discuss how the two masses are related to the Planck constant and other coupling constants and if the Kibble balance could be used to test the dynamic constants theories in Dirac cosmology.

physics.gen-ph↗

arXiv2024

Testing CCC+TL Cosmology with Observed BAO Features

The primary purpose of this paper is to see how well a recently proposed new model fits (a) the position of the baryon acoustic oscillations (BAO) features observed in the large-scale distribution of galaxies and (b) the angular size measured for the sound horizon due to BAO imprinted in the cosmic microwave background (CMB) anisotropy. The new model is a hybrid model that combines the tired light (TL) theory with a variant of the $ΛCDM$ model in which the cosmological constant is replaced with a covarying coupling constants' (CCC) parameter $α$. This model, dubbed the CCC+TL model, can fit the supernovae type 1a Pantheon+ data as accurately as the $ΛCDM$ model, and also fit the angular size of cosmic dawn galaxies observed by the James Webb Space Telescope, which is in tension with the $ΛCDM$ model. The results we obtained are $151.0 (\pm5.1)$ Mpc for the absolute BAO scale at the current epoch, and the angular size of the sound horizon $θ_{sh}=0.60°$ matching Planck's observations at the surface of the last scattering when the baryon density is set to 100% of the matter density and |$α$| is increased by 5.6%. It remains to be seen if the new model is consistent with the CMB power spectrum, the big-bang nucleosynthesis of light elements, and other critical observations.

astro-ph.CO↗

arXiv2023

Dynamical analysis of the covarying coupling constants in scalar-tensor gravity

A scalar-tensor theory of gravity is considered wherein the gravitational coupling $G$ and the speed of light $c$ are admitted as space-time functions and combine to form the definition of the scalar field $ϕ$. The varying $c$ participates in the definition of the variation of the matter part of the action; it is related to the effective stress-energy tensor which is a result of the requirement of symmetry under general coordinate transformations. The effect of the cosmological coupling $Λ$ is accommodated within a possible behaviour of $ϕ$. We analyze the dynamics of $ϕ$ in the phase space, thereby showing the existence of an attractor point for reasonable hypotheses on the potential $V(ϕ)$ and no particular assumption on the Hubble function. The phase space analysis is performed both with the linear stability theory and via the more general Lyapunov's method. Either method lead to the conclusion that the condition $\dot{G}/G=σ\left(\dot{c}/c\right)$ where $σ=3$ must hold for the rest of cosmic evolution after the system gets to the globally asymptotically stable fixed point and the dynamics of $ϕ$ ceases. This result provides a physical foundation for the phenomenological model admitting $\left(G/G_{0}\right)=\left(c/c_{0}\right)^{3}$ used recently to interpret cosmological and astrophysical data. The thus co-varying couplings $G$ and $c$ impact the cosmic evolution after the dynamical system settles to equilibrium. This impact is investigated by constructing the generalized continuity equation in our scalar-tensor model and considering two possible regimes for the varying speed of light -- decreasing $c(a)$ and increasing $c(a)$ -- while solving our modified Friedmann equations. The solutions to the latter equations make room for radiation- and matter-dominated eras that progress to a dark-energy-type of accelerated expansion.

gr-qc↗

arXiv2023

Constraining Co-Varying Coupling Constants from Globular Cluster Age

Equations governing the evolution of a star involve multiple coupling constants. Thus, the time it spends as a main-sequence star can be expected to depend on whether or not such constants vary over the time scale of stellar evolution. When the star belongs to a globular cluster, the star's age cannot exceed that of the globular cluster, and the latter cannot exceed the age of the Universe. This fact can be used to constrain or verify the variation of the coupling constants, i.e., the speed of light c, the gravitational constant G, the Planck constant h, and the Boltzmann constant k. We have estimated the age of the main-sequence star analytically from the time it takes to synthesize all its hydrogen into helium under fixed and varying coupling constants scenarios. When we permitted the interrelated variation of the four constants ($G\thicksim c^{3}\thicksim h^{3}\thicksim k^{3/2}$) and differentiated between the cosmological energy and local energy conservation laws, we could show that the variation of the constants established in our earlier studies, i.e., $(\dot{G}/G)_{0}=3(\dot{c}/c)_{0}=(\dot{h}/h)_{0}=1.5 (\dot{k}/k)_{0}=5.4H_{0} =3.90(\pm 0.04)\times 10^{-10} yr^{-1}$ at the current cosmic time is consistent with the present work. Nevertheless, the challenge remains to come up with an experiment, astrometric or terrestrial, that can unequivocally prove or falsify the predicted variation.

astro-ph.CO↗

arXiv2023

Constraining Coupling Constants' Variation with Supernovae, Quasars, and GRBs

Dirac, in 1937 proposed the variation of coupling constants derived from his large number hypothesis. Efforts have continued since then to constrain their variation by various methods. We briefly discuss several methods used for the purpose while focusing primarily on the use of supernovae type 1a, quasars, and gamma-ray bursts (GRBs) as cosmological probes for determining cosmological distances. Supernovae type Ia (SNeIa) are considered the best standard candles since their intrinsic luminosity can be determined precisely from their light curves. However, they have only been observed up to about redshift $z=2.3$, mostly at $z<1.5$. Quasars are the brightest non-transient cosmic sources in the Universe. They have been observed up to $z=7.5$. Certain types of quasars can be calibrated well enough for their use as standard candles but with a higher degree of uncertainty in their intrinsic luminosity than the SNeIa. GRBs are even brighter than quasars, observed up to $z=9.4$. Their radiation lasts from 10s of milliseconds to several minutes and, in rare cases, for a few hours. However, they are even more challenging to calibrate as standard candles than quasars. What if the standard candles' intrinsic luminosities are affected when the coupling constants become dynamic? This paper uses our earlier finding that the speed of light c, the gravitational constant G, the Planck constant h, and the Boltzmann constant k variations are correlated as $G\thicksim c^{3}\thicksim h^{3}\thicksim k^{3/2}$ with $(\dot{G}/G)_{0}=3(\dot{c}/c)_{0}=(\dot{h}/h)_{0}=1.5 (\dot{k}/k)_{0}=5.4H_{0} =3.90(\pm 0.04)\times 10^{-10} yr^{-1}$ corroborates it with SNeIa, quasars, and GRBs observational data. Also, we show that this covarying coupling constant model may be better than the standard ΛCDM model for using quasars and GRBs as standard candles and predict the mass of the GRBs scales as $((1+z)^{1/3}-1)$.

astro-ph.CO↗

arXiv2022

Constraining variability of coupling constants with bright and extreme quasars

The 'extreme Population A (xA) quasars' approaching, sometimes exceeding the Eddington limit, are a type of quasars that could serve as a standard candle to measure distances too large for supernovae type Ia (SNe Ia) to be observable. For using xA quasars as standard candles, it would be beneficial to know how their luminosities would vary if coupling constants varied over cosmic time. Alternatively, when calibrated using SN Ia standard candle, xA quasar observations could constrain the variation of coupling constants. We show that the Hubble diagram of xA quasars provides the same constraint on the constants' variation as the Hubble diagram of SNe Ia from the Pantheon data. The coupling constants vary concurrently in our model, i.e., the variation of the speed of light $c$, the gravitational constant $G$, the Planck constant $h$, and the Boltzmann constant $k$, are interrelated as $G\thicksim c^{3}\thicksim h^{3}\thicksim k^{3/2}$. The constraint thus determined can be expressed in terms of the Hubble constant $H_{0}$ as $(\dot{G}/G)_{0}=3(\dot{c}/c)_{0}=3(\dot{h}/h)_{0}=1.5 (\dot{k}/k)_{0}=5.4H_{0} =3.90(\pm 0.04)\times 10^{-10} yr^{-1}$, where subscript 0 is for the current time. This conclusion is corroborated with the analysis of data on the quasars with correlated UV and X-ray emissions.

gr-qc↗

arXiv2022

Varying physical constants and the lithium problem

We have used the recently published varying physical constants (VPC) approach to resolve the primordial lithium abundance problem. The value of the ratio of $7Li$ to hydrogen $7Li/H=1.400(\pm 0.023){\times}10^{-10}$ we have calculated using this approach is about four times lower than that estimated using the standard lambda cold dark matter ($Λ$CDM) cosmological model, and is consistent with the most agreed observational value of $1.6(\pm 0.3){\times}10^{-10}$. In the VPC approach Einstein equations are modified to include the variation of the speed of light $c$, gravitational constant $G$ and cosmological constant $Λ$ using the Einstein-Hilbert action. Application of this approach to cosmology naturally leads to the variation of the Plank constant $\hbar$ and the Boltzmann constant $k_B$ as well. They approach fixed values at the scale factor $a\ll 1$: $c=c_0/e$, $G=G_0/e^3$, $\hbar=\hbar_0/e$ and $k_B=k_{B0}/e^{5/4}$, where $e$ is the Euler's number (=2.7183). Since the VPC cosmology reduces to the same form as the $Λ$CDM cosmology at very small scale factors, we could use an existing Big-Bang nucleosynthesis (BBN) code AlterBBN with the above changes to calculate the light element abundances under the VPC cosmology. Among other abundances we have calculated at baryon to photon ratio $η=6.1{\times}10^{-10}$ are: $4He/H =0.2478 (\pm 0.041)$, $D/H =2.453(\pm 0.041){\times}10^{-5}$ and $3 He/H=2.940(\pm 0.049){\times}10^{-5}$.

gr-qc↗

arXiv2021

Effect of evolutionary physical constants on type-1a supernova luminosity

Type 1a supernovae, SNeIa, are used as standard candles in cosmology for determining the distances of the galaxies harboring them. We show that the luminosity of an SNIa depends on its distance from us when physical constants (the speed of light $c$, the gravitational constant $G$, and the Planck constant $h$) are permitted to evolve. It is because the Chandrasekhar mass of the white dwarf that explodes to create SNIa depends on the values of the constants at the epoch the SNIa is formed. We show that the SNeIa luminosities were up to about four times higher in the past than they are now. Thus, the luminosity distance estimation of the earliest SNeIa could be off by up to a factor of two. Cosmological parameters, determined with this correction applied to the redshift vs. distance modulus database (Pantheon SNeIa), are not very different from those from the standard $Λ$CDM model without this correction, except for the dark-energy density and the curvature energy density; the latter increases at the cost of the former. Variations of the constants are given by $\dot{G}/G=3.90(\pm 0.04)\times 10^{-10} yr^{-1} $ and $\dot{c}/c=\dot{h}/h=1.30(\pm 0.01)\times 10^{-10} yr^{-1} $ at present. These variations are valid only when $G$, $c$, and $h$ are permitted to vary concurrently rather than individually.

gr-qc↗

arXiv2020

Cosmology with relativistically varying physical constants

We have shown that the varying physical constant model is consistent with the recently published variational approach wherein Einstein equations are modified to include the variation of the speed of light c, gravitational constant G and cosmological constant Λ using the Einstein-Hilbert action. The general constraint resulting from satisfying the local conservation laws and contracted Bianchi identities provides the freedom to choose the form of the variation of the constants as well as how their variations are related. When we choose dG/Gdt=3dc/cdt, c=c_0.exp[(a^α-1)], G=G_0.exp[3(a^α-1)] and Λ=Λ_0.exp[(a^(-α)-1)], where a is the scale factor and α=1.8, we are able to show that the resulting model: (a) fits the supernovae 1a observational data marginally better than the ΛCDM model; (b) determines the first peak in the power spectrum of the cosmic microwave background temperature anisotropies at multipole value of l=217.3; (c) calculates the age of the universe as 14.1 Gyr; and (d) finds the BAO acoustic scale to be 145.2 Mpc. These numbers are within less than 3% of the values derived using the ΛCDM model. Surprisingly we find that the dark-energy density is negative in a universe that has significant negative curvature and whose expansion is accelerating at a faster rate than predicted by the ΛCDM model.

astro-ph.CO↗

arXiv2018

SNe Ia Redshift in a Non-Adiabatic Universe

By relaxing the constraint of adiabatic universe used in most cosmological models, we have shown that the new approach provides a better fit to the supernovae Ia redshift data with a single parameter, the Hubble constant $H_0$, than the standard $Λ$CDM model with two parameters, $H_0$ and the cosmological constant $Λ$ related density $Ω_Λ$. The new approach is compliant with the cosmological principle. It yields the H_0=68.28 (+- 0.53) km s-1Mpc-1 with an analytical value of the deceleration parameter q_0=-0.4. The analysis presented is for a matter only, flat universe. The cosmological constant $Λ$ may thus be considered as a manifestation of a non-adiabatic universe that is treated as an adiabatic universe.

physics.gen-ph↗