Equation of State and Mass-Radius Relations of Quadratic Generalized Uncertainty Principle-modified White Dwarfs with Arbitrary Temperatures

We study the mass-radius relations of finite temperature white dwarfs modified by the quadratic generalized uncertainty principle (QGUP), a prediction that arises from quantum gravity phenomenology. This QGUP approach extends the Heisenberg uncertainty principle by a quadratic term in momenta, which then modifies the phase space volume in the Chandrasekhar equation of state (EoS). This EoS was first calculated by treating the GUP parameter $\beta$ as perturbative. This perturbative EoS exhibits the expected thermal deviation for low pressures, while showing conflicting behaviors in the high pressure regime dependent on the sign of the $j$th order of approximation, $(\mathcal{O}(\beta^j))$. To explore the effects of QGUP further, we proceed with a full numerical simulation, and showed that in general, finite temperatures cause the EoS at low pressures to soften, while QGUP stiffens the EOS at high pressures. This modified EoS was then applied to the Tolman-Oppenheimer-Volkoff equations and its classical approximation to obtain the modified mass-radius relations for general relativistic and Newtonian white dwarfs. The relations for both cases were found to exhibit the expected thermal deviations at small masses, where low-mass white dwarfs are shifted to the high-mass regime at large radii, while high-mass white dwarfs acquire larger masses, beyond the Chandrasekhar limit. Additionally, we find that for sufficiently large values of the GUP parameter and temperature, we obtain mass-radius relations that are completely removed from the ideal case, as high-mass deviations due to GUP and low-mass deviations due to temperature are no longer mutually exclusive

Radial Oscillations and Dynamical Instability Analysis for Linear GUP-modified White Dwarfs

A modification to the Heisenberg uncertainty principle is called the generalized uncertainty principle (GUP), which emerged due to the introduction of a minimum measurable length, common among phenomenological approaches to quantum gravity. An approach to GUP called linear GUP (LGUP) has recently been developed that satisfies both the minimum measurable length and the maximum measurable momentum, resulting to a phase space volume proportional to the first-order momentum $(1 - \alpha p)^{-4} d^3x d^3p$, where $\alpha$ is the still-unestablished GUP parameter. In this study, we explore the mass-radius relations of LGUP-modified white dwarfs, and provide them with radial perturbations to investigate the dynamical instability arising from the oscillations. We find from the mass-radius relations that LGUP results to a white dwarf with a lower maximum mass, and this effect gets more apparent with larger the values of $\alpha$. We also observe that the mass of the white dwarf corresponding to the vanishing of the square of the fundamental frequency $\omega_0$ is the maximum mass the white dwarf can have in the mass-radius relations. The dynamical instability analysis also shows that instability sets in for all values of the GUP parameters $\alpha$, and at lower central densities $\rho_c$ (corresponding to lower maximum masses) for increasing $\alpha$, which verifies the results obtained from the mass-radius relations plots. Finally, we note that the mass limit is preserved for LGUP-modified white dwarfs, indicating that LGUP supports gravitational collapse of the compact object

Seasonal dependence of geomagnetic field variations on the ground associated with geomagnetic sudden commencements

2011 International Union of Geodesy and Geophysics (IUGG) General Assembly, 28 June -7 July 2011, Melbourne Australi

Seasonal dependence of magnetic field variations from subauroral latitude to the magnetic equator during geomagnetic sudden commencements

AGU 2010 Fall Meeting, 2010年12月16

磁気赤道-低緯度域における磁気急始(SC)の磁場振幅の季節変化について

日本地球惑星科学連合2013年大会, 2013/05/19-24, 幕張メッセ(千葉県

高緯度から磁気赤道域における磁気急始(SC)の磁場振幅の季節依存性について

名古屋大学太陽地球環境研究所・研究集会第3回電磁圏物理学シンポジウム, 2011/02/28-03/01, 福

高緯度から磁気赤道までの磁気急始(SC)の磁場振幅の季節変化の緯度依存性

地球電磁気・地球惑星圏学会 第130回総会・講演会; 会場・会期: 神戸大学六甲台第2キャンバス; 2011年11月3日～6