arXiv subjects

Narayanankutty Karuppath

Publications and source records attributed to Narayanankutty Karuppath.

6 recordsLinked to original sources

arXiv2026

An Interior model of Charged Fluid Spheres

At constant time $t$, we examine the Vaidya-Tikekar metric characterising a three-dimensional, extremely dense spheroidal star configuration. The static, spherically symmetric solution of Einstein's field equations can be expressed in analytic closed form utilising a hypergeometric series. A relativistic, superdense state of matter at a constant $t$ is represented by the resultant model, which describes the geometry of a three-spheroid. Assuming a stellar density of $ρ_{a}= 2*10^{14} gm*cm^{-3}$, we investigate configurations whose total mass and radius vary over a range of well-defined values of the density variation parameter. Similar to an uncharged neutron star, all models possess the same total mass and boundary radius. The hypergeometric solution leads to a new class of exact, physically acceptable solutions. We show that the model satisfies the conditions of hydrostatic equilibrium and fulfils all standard energy conditions, which are verified throughout the analysis.

gr-qc↗

arXiv2026

A Precise Ultra - Dense Star Model on Spheroidal Space-Time

This study presents a static, spherically symmetric configuration in which the interior geometry of a relativistic superdense star is modeled as a three-spheroid with constant $t_1$. The model is constructed using an analytical closed-form solution to Einstein's field equations. Assuming a characteristic density of $ρ_{a}= 2\times10^{14} \mathrm{g\,cm^{-3}}$, we compute the total mass and radius of the star based on a prescribed set of structural parameters that influence the density profile. The resulting stellar configurations exhibit boundary radii and total masses comparable to those of neutron stars with vanishing charge density. New exact solutions are obtained by solving the relevant second-order ordinary differential equations. We demonstrate that these solutions satisfy the standard energy conditions and maintain hydrostatic equilibrium throughout the stellar interior. All physical requirements remain valid at every point within the configuration. In this framework, the parameter $λ=\frac{ρ_{a}}{ρ_{0}}$ serves as a key determinant of the mass-radius relationship. We further assess the suitability of the model for representing a relativistic superdense star and analyze its stability under radial perturbations. The investigation indicates that, for the configuration to remain dynamically stable, the density ratio between the outer and inner regions must take the value $λ= 0.4$.

gr-qc↗

arXiv2025

Variations of the Ca II K Line Profile Parameters with Solar Latitude and Time Observed from Kodaikanal Solar Observatory

The Calcium-K line profiles as functions of solar latitude and time were obtained through our observations from the Kodaikanal Solar Observatory using the solar tunnel telescope and spectrograph with a CCD detector. Observations were conducted on all days with favourable sky conditions. We analysed the data collected over a period of about ten years to study the variations in the Ca II K line profiles recorded between 2015 and 2024, of which 709 days of data were found useful. The temporal and time-averaged latitudinal variations of the K$_{1}$ width, K$_{2}$ width, K$_{3}$ intensity and the intensity ratios of K$_{2v}$/K$_{2r}$ and K$_{2v}$/K$_{3}$ were computed using a semi-automated program. The parameters showed asymmetric increases towards the higher latitudes, with the rates of increase being higher in the southern hemisphere. The temporal plots for K$_{1}$ width and K$_{3}$ intensity showed positive correlations with the plage and spot filling factors, whereas the temporal plots for K$_{2}$ width, K$_{2v}$/K$_{2r}$ and K$_{2v}$/K$_{3}$ intensity ratios showed negative correlations. The time-averaged latitudinal plot for K$_{1}$ width has small peaks near 25°N and 20°S. The K$_{2}$ width has a small peak at 0°. The K$_{3}$ intensity has peaks at 20°N and 15°S. The K$_{2v}$/K$_{2r}$ intensity ratio shows peaks at 50$\degree$N, 0° and 40°S. The K$_{2v}$/K$_{3}$ intensity ratio shows peaks at 60°N, 0° and 60°S. Slope profiles show spectral response to magnetic activity peaks near K$_{3}$ with north-south asymmetries. Such variations in the line profiles are important in the studies of solar irradiance, surface flux transport and solar dynamo.

astro-ph.SR↗

arXiv2018

Multi-Wavelength Correlation Studies Of Diffuse Emission From The Aquila Rift

We present a multi-wavelength correlation study of diffuse ultraviolet radiation using GALEX observations towards the Aquila Rift. Apart from airglow and zodiacal emissions, we find a diffuse background of 1300 - 3700 \photu\ in the far-ultraviolet (FUV: 1350 - 1750 Å) band and 1300 - 2800 \photu\ in the near-ultraviolet (NUV: 1750 - 2850 Å) band. The observed diffuse UV emissions are saturated with total as well as neutral hydrogen column density in the region due to high optical depth in UV ($τ$: 0.91-23.38). Higher values of FUV/NUV ratio in the region, greater than the threshold value of 0.6, along with the positive correlation between the ratio and FUV intensity are due to excess emission in the FUV band which is absent in the NUV band. We estimated the excess emission to be in the range $\sim$ 400 - 2700 \photu, plausibly due to H$_2$ fluorescence, ion line emissions and two-photon continuum emissions from the region in the FUV band, which also shows saturation in optically thick regions with N(H$_{2}$) as well as H$α$ emissions. Since N(H$_{2}$) and H$α$ emissions spread all over the region, the excess emission from the field is composite in nature and a detailed spectroscopic analysis is needed to disentangle the contribution from individual components.

astro-ph.GA↗

arXiv2015

Diffuse Radiation from the Aquila Rift

We present an analysis of the diffuse ultraviolet (UV) background in a low latitude region near the Aquila Rift based on observations made by the Galaxy Evolution Explorer (GALEX). The UV background is at a level of about 2000 ph cm^-2 s^-1 sr^-1 Å^-1 with no correlation with either the Galactic latitude or the 100 micron infrared (IR) emission. Rather, the UV emission falls off with distance from the bright B2 star HIP 88149, which is in the centre of the field. We have used a Monte Carlo model to derive an albedo of 0.6 - 0.7 in the UV with a phase function asymmetry factor (g) of 0.2 - 0.4. The value for the albedo is dependent on the dust distribution while g is determined by the extent of the halo.

astro-ph.GA↗

arXiv2009

Quantum Non-Locality and Universe

The notion of Non-Locality (NL) in physics has great epistemological implications and impact on the perceptive of Reality. Numerous counter intuitive experimental results that clearly violate Bell's inequality have prompted several physicists to believe in 'mysterious' non-local correlations particularly in quantum systems of EPR type. Not commenting much on whether NL is true or not, our contention is that NL, in general, leads to the concept of holistic universe and further to a global concept of 'Consciousness-Centered-Cosmos' (CCC) as almost inevitable rational outcome. These suggestions though ostensibly unorthodox, are rather within rational and legitimate frame work of science. Our reasoning is quite distinct from the erstwhile doctrine of the role of consciousness in the measurement problem and state vector reduction although the latter may add further credence to the our contention. We address particularly the implications NL and discuss certain related aspects of new quantum world view in general. The less recognized association of the principles of uncertainty with locality, causality, the arrow of time and reality are brought out. Perhaps these underpinnings are much less appreciated than necessary.

physics.gen-ph↗