arXiv subjects

Navaneeth Poonthottathil

Publications and source records attributed to Navaneeth Poonthottathil.

7 recordsLinked to original sources

arXiv2026

Characterization of an MPPC-Based Scintillator Telescope and Measurement of Cosmic Muon Angular Distribution

This report presents the design, characterization, and application of a high-sensitivity optical detection system based on plastic scintillators coupled to Multi-Pixel Photon Counters (MPPCs). The primary objective was to evaluate the performance of MPPCs (Silicon Photomultipliers) as robust, low-voltage alternatives to traditional photomultiplier tubes for detecting faint scintillation light. The optoelectronic properties of the sensors were analyzed, including single-photoelectron gain calibration and dark count rate measurements, to optimize the signal-to-noise ratio. By embedding wavelength-shifting fibers to enhance light collection efficiency, the system was configured into a three-fold coincidence telescope. The angular distribution of the cosmic ray muon flux was measured to validate the detector's stability and geometric acceptance. Fitting the experimental data to a $\bm{\cos^n(\theta)}$ distribution yielded an angular exponent of $\bm{n = 1.44 \pm 0.06}$, consistent with literature values. These results demonstrate the efficacy of the MPPC-scintillator coupling for precise photon counting and timing applications in high-energy physics instrumentation.

physics.ins-det↗

arXiv2024

On the Interrelation of the Generalized Holographic Equipartition and Entropy Maximization in Kaniadakis Paradigm

This study examines the compatibility of the generalized holographic equipartition proposed in ref \cite{sheykhi2013friedmann} with the maximization of horizon entropy in an (n + 1)-dimensional non-flat Friedmann-Robertson-Walker (FRW) universe. Here, the entropy associated with the apparent horizon is described by Kaniadakis entropy, as well as truncated Kaniadakis entropy, which is expanded and truncated to third order when the Kaniadakis parameter $(K)$ is small, indicating minor deviations from the standard Bekenstein-Hawking entropy. Initially, we derive the conditions required for maximizing both Kaniadakis horizon entropy and truncated Kaniadakis horizon entropy. We then examine whether the generalized holographic equipartition aligns with the constraints of horizon entropy maximization. Our findings reveal that the generalized holographic equipartition is consistent with the maximization of Kaniadakis horizon entropy and truncated Kaniadakis horizon entropy in a universe with non-zero spatial curvature.

gr-qc↗

arXiv2024

Observational Evidence to Logistic Dark Energy Driving the Accelerating Universe

We present logistic dark energy model (LDEM), where the dark energy density follows a logistic function for the scale factor. The equation of state parameter of dark energy ($w_D$) transitioned from $-1$ in the distant past to its current value of $-0.76$, closely resembling the $\Lambda$CDM model in the early epoch and showing significant deviation in the late phase. The evolution of the deceleration parameter in the LDEM signifies its success in explaining the late-time cosmic acceleration. Model selection based on the Bayesian Information Criterion (BIC), incorporating observations from Type Ia Supernovae (SNe Ia), Observational Hubble data (OHD), and Baryon Acoustic Oscillation (BAO) strongly favors the LDEM over the conventional $\Lambda$CDM model, where BIC is estimated to be $\sim -20$. Incorporating the shift parameter derived from the Cosmic Microwave Background (CMB) data shows competing evidence of the LDEM over the standard $\Lambda$CDM. Remarkably, the Hubble constant ($H_0$) value computed using any of the datasets tends to align closely with the predictions from the Cosmic Microwave Background (CMB), suggesting a need to reconsider the local measurement.

astro-ph.CO↗

arXiv2024

Scalar Field Dominated Cosmology with Woods-Saxon Like Potential

Dark energy can be characterized by a canonical scalar field, known as quintessence. Quintessence allows for a dynamical equation of state $-1 \le \omega \le -\frac{1}{3}$. A previous study by Oikonomou and Chatzarakis have shown that a scalar field model with a Woods-Saxon like potential can successfully explain the early inflation. In this work, we consider a quintessence model with a potential of similar form to explain the late time acceleration. The model is studied at late phase assuming flat cosmology, and the model parameters are constrained using Type Ia supernova data and Observational Hubble data. In particular we employ Markov Chain Monte Carlo methods for the Bayesian inference of these parameters. We obtain the value of the Hubble constant $H_0 \sim 68 \text{ km s}^{-1} \text{Mpc}^{-1}$ and the matter energy density parameter $\Omega_{m_0} \sim 0.30 $, which are in close agreement with the values obtained from the Planck CMB data, assuming the $\Lambda$CDM model. Computation of the $\chi^2_{min}$, AIC and BIC reveal that this model is slightly preferred according to AIC and $\chi^2_{min}$ criteria, while the $\Lambda$CDM is preferred according to BIC. We demonstrate that the model possesses a stable attractor in the asymptotic future, which confirms the dynamical stability of the model. Thus, this model may be considered as a potential alternative to the $\Lambda$CDM.

astro-ph.CO↗

arXiv2024

Emergence of Cosmic Space and Horizon Thermodynamics from Kaniadakis Entropy

Utilizing Kaniadakis entropy associated with the apparent horizon of the Friedmann-Robertson-Walker (FRW) Universe and applying the emergence of cosmic space paradigm, we deduce the modified Friedmann equation for a non-flat (n+1)-dimensional universe. Employing the first law of thermodynamics, we arrive at the same modified Friedmann equation, showing the connection between emergence of cosmic space and first law of thermodynamics. We also establish the condition to satisfy the Generalized second law of thermodynamics within the Kaniadakis framework. Our study illuminates the intricate connection between the law of emergence and horizon thermodynamics, offering a deeper insight through the lens of Kaniadakis entropy.

gr-qc↗

arXiv2023

Observational evidence for parametrized emergent dark energy models

Recent cosmological observations show a statistically significant tension in the estimated values of the cosmological parameters within the standard $\Lambda$CDM framework. In a recent study, Li and Shafieloo introduced a simple Phenomenological Emergent Dark Energy (PEDE) model, which possesses the same number of parameters as that of the $\Lambda$CDM model. Their research highlighted this model as a viable alternative to $\Lambda$CDM, capable of alleviating the Hubble tension and explaining the late-time cosmic acceleration. Following this, we consider a series of PEDE-type models where a new parameter $b$ is introduced in the dark energy expression that distinguishes one model from the other and is designated as bPEDE models. The PEDE and $\Lambda$CDM models were the special cases of the bPEDE model. In contrast to the PEDE model, the bPEDE model demonstrates the presence of dark energy in the past while indicating its absence in the asymptotic future. Confronting these models with the observational Hubble data (OHD) shows that a series of bPEDE models fit the data better than the PEDE model and the standard $\Lambda$CDM model. Notably, the Hubble constant ($H_0$) value computed using the best-fit bPEDE models closely aligns with the CMBR prediction. It significantly deviates from the local measurement at a significance level of approximately $3.4\sigma$ for the model independent OHD data combination. The outcome suggests reconsidering the systematic uncertainties associated with the local measurement. The best-fit bPEDE models predict the deceleration to acceleration transition at a redshift $z_T \sim 0.78$ which is in close agreement with the $\Lambda$CDM prediction. The age of the universe predicted by the bPEDE model is $\sim 14$ Gyr, slightly higher than the age predicted by the $\Lambda$CDM model. The statefinder trajectory reveals a quintessence nature of dark energy.

astro-ph.CO↗

arXiv2023

Testing the dynamical stability and validity of generalized second law within the phantom dynamical dark energy model

Hubble constant($H_0$) tension and tension in the matter fluctuation amplitude ($s_8$) are fascinating puzzles in cosmology nowadays. Phantom dynamical dark energy model (PDDE), also known as little sibling of the big rip is an abrupt event that can happen in the far future evolution of the universe. Recent analysis of PDDE model based on CMBR data shows that the model is a potential candidate to alleviate these tension problems. In this work, we study the background evolution of the universe within the PDDE model. Analysis based on the SNIa+BAO+OHD data shows that the model is successful in explaining the late phase acceleration of the universe. Also, the values of the cosmological parameters predicted by PDDE model are consistent with the values predicted by the $\Lambda$CDM model. However, most of the phanton dark energy models doesn't give stable solution in the asymptotic future. In this regard, we address the dynamical stability of the PDDE model and also test the validity of the generalized second law (GSL) of thermodynamics. We show that the model is dynamically unstable and violates the GSL. The model doesn't satisfy the convexity condition and hence the universe doesn't behave like an ordinary macroscopic system within the PDDE model.

gr-qc↗