DOCSLIB.ORG

Dark Energy Stars: Stable Configurations

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Dark Energy Stars: Stable Configurations Canadian Journal of Physics Dark energy stars: Stable configurations Journal: Canadian Journal of Physics ManuscriptFor ID cjp-2017-0526 Review Only Manuscript Type: Article Date Submitted by the Author: 19-Jul-2017 Complete List of Authors: Bhar, Piyali; Jadavpur University, Mathematics Manna, Tuhina; St. Xavier's College, Commerce Rahaman, Farook; Jadavpur University, Mathematics Banerjee, Ayan; Jadavpur Univ, Mathematics Dark energy, Stellar equilibrium, Exact solution, Specific mass function, Keyword: junction conditions Is the invited manuscript for consideration in a Special N/A Issue? : https://mc06.manuscriptcentral.com/cjp-pubs Page 1 of 10 Canadian Journal of Physics Dark energy stars: Stable configurations Piyali Bhar∗ Department of Mathematics, Government General Degree College, Singur, Hooghly 712 409, West Bengal, India Tuhina Mannay Department of Commerce (Evening), St. Xaviers College, 30 Mother Teresa Sarani, Kolkata 700016, West Bengal, India Farook Rahamanz and Ayan Banerjeex Department of Mathematics, Jadavpur University, Kolkata-700032, India (Dated: April 12, 2018) In present paper a spherically symmetric stellar configuration has been analyzed by assuming the matter distribution of the stellar configuration is anisotropic in nature and compared with the realistic objects, namely, the low mass X-ray binaries (LMXBs) and X-ray pulsars. The analytic solution has been obtained by utilizing the dark energy equation of state for the interior solution corresponding to the Schwarzschild exterior vacuum solution at the junction interface. Several phys- ical properties like energy conditions, stability, mass-radius ratio, and surface redshift are described through mathematical calculations as well as graphical plots. It is found that obtained mass-radius ration of the compact stars candidates like 4U 1820-30, PSR J 1614-2230, Vela X-1 and Cen X- 3are very much consistent with the observed data by Gangopadhyay et al. (Mon. Not. R. Astron. Soc. 431, 3216 (2013)).For So our Review proposed model would Only be useful in the investigation of the possible clustering of dark energy. PACS numbers: I. INTRODUCTION and dark matter. There is hardly any other topic in general relativity In 2005 physicist George Chaplin proposed that, grav- which is as extensively researched as black holes. Since itational collapse of objects with masses greater than a Oppenheimer and Snyder [4] first attempt at explaining few solar masses should lead to the formation of a com- the state of gravitational collapse of a black hole, there pact object called dark energy star whose surface corre- have been various observational data favouring the exis- sponds to a quantum critical surface for space-time, and tence of event horizon, but nonesoever proving it [5]. This whose interior differs from ordinary space-time only in in turn has lead to the developement of a plura of fasci- having a much larger vacuum energy [1]. He claimed nating alternative ideas. One such popular model is that that the current picture of gravitational collapse as ex- of a gravastar or gravitationally vacuum star as proposed plained in terms of event horizon is physically inconsis- by Mazur and Mottola [6]. Its a compact object having tent since it conflicts with quantum mechanics [2]. The an interior de Sitter condensate defined by the equation theory states that infalling matter gets converted to dark of state p = −ρ , matched to a shell of finite thickness energy as it falls through the event horizon causing the with an equation of state p = ρ , which is again matched space inside the event horizon to have a high value of cos- to an exterior Schwarzschild vacuum solution. This star mological constant and hence a high negative pressure to has no singularity at the origin and no event horizon since exert against gravity. This high negative pressure may the thick shell surface with a radius slightly greater than counter the mass the star gains thus avoiding a singu- the Schwarzschild radius, replaces both the de Sitter and larity. Thus there is a sort of phase transition occurring the Schwarzschild horizons. The charged and uncharged in the phase of space at the event horizon [2, 3]. In fact model of gravastar was obtained in our earlier works [7]. Dark energy star may account for high energy cosmic ray A modified version of the gravastar was studied by Cat- sources and positron sources since infalling masses decays toen et al. [8] using a continuous pressure profile without into lighter masses at the event horizon accelerating pro- thin shells. It strongly suggested an anisotropic pres- ton decay. This proposal may provide a new perspective sure model. Later an alternative model termed as Born- on spectacular astrophysical phenomena including super- Infeld phantom gravastar was constructed replacing the novae explosions, gamma ray bursts, positron emission, de-Sitter spacetime by an interior spacetime governed by the Chaplygin gas equation of state [9]. In this paper the authors have investigated a generalized case in which the equation of state is governed by the equation of state ∗Electronic address: [email protected] yElectronic address: [email protected] p = !ρ matched to an exterior vacuum solution. The zElectronic address: [email protected] proposed stellar model consists of five zones : an inte- xElectronic address: [email protected] rior core, a thin shell between the core and the interior https://mc06.manuscriptcentral.com/cjp-pubs Canadian Journal of Physics Page 2 of 10 2 spacetime, the interior spacetime and a thin shell which the exterior vacuum region is obtained [15]. Yadav et acts as a junction interface between the interior and the al. [16] have given a dark energy model with a variable exterior Schwarzschild spacetime. This kind of compact equation of state parameter. Inspired by the prior men- object which generalizes a gravatus model by using equa- tioned works of Cattoen et al. [8] and Ruderman(1972) tion of state p = !ρ with ! < −1=3 is called a dark [20] we have taken the pressure inside the fluid sphere in energy gravastar or simply a dark energy star , as re- our model to be anisotropic. For an anisotropy distribu- ferred by Chapline. This terminology is motivated by the tion, the pressure inside the fluid sphere is decomposed fact that dark energy is still unknown component of our into two orthogonal components: radial pressure pr and Universe has relativistic negative pressure. The 1998 ob- transverse pressure pt where obviously pr =6 pt. Stud- servations of Type la Supernova [10] confirms that dark ies on X-ray pulsars, Her-x-1, X-ray buster 4U 1820-30, energy is responsible for the phase of cosmic accelera- millisecond pulsar SAXJ1804.4-3658 etc. suggests that tion. Numerous other recent observations of Cosmic Mi- nuclear matter tends to become anisotropic in nature at crowave Background(CMB) anisotropies and Large Scale very high densities ( 1015gm=cc.) [21, 22]. Anisotropy Structure(LSS) [11] reconfirm this characteristics of small may occur due to any of the following reasons : exis- redshift evolution of our Universe. The simplest explana- tence of solid core, a type 3A superfluid [23], phase transi- tion of dark energy is the cosmological constant Λ which tion [24], pion condensation [25], rotation, magnetic field, is usually interpreted physically as a vacuum energy, with mixture of two fluid, existence of external field etc. p = −ρ. Another possible way to explain the dark energy We organised the paper as follows : In Sec. II. deals is by invoking an equation of state, p = !ρ with ! < 0 , with the basic field equations and their solutions, then where p is the spatially homogeneous pressure and ρ the the junction conditions have been discussed in Sec. III. energy density of the dark energy,For instead Review of the constant In Only Sec. IV. the physical properties with the stability con- vacuum energy density. The models of dark energy with ditions have been studied. Finally, in Sec. V. we discuss ! > −1 mainly comprises of quintessence , k-essence and some specific comments regarding the results obtained in chaplygin gas among others. the study. This idea of dark energy star theorizes that the sur- face of a compact object is a quantum critical shell with II. INTERIOR SPACE-TIME AND THE FIELD some thickness z [12]. When ordinary elementaryq par- EQUATIONS M0 ticles which have energy beyond Q0 = 100MeV , M We consider a static spherically symmetric space-time where M is the solar mass, enter this quantum critical 0 given by the following line element: region they decay into substituent products and radiation [ Z ] that gets directed backwards from the surface of dark en- 1 dr2 ds2 = −exp −2 g(~r)dr~ dt2 + + r2dΩ2; (1) ergy star perpendicular to the critical surface. However − 2m r 1 r for particles with energy < Q0 will pass through the crit- ical surface and follow diverging geodesics in the interior where r denotes the radial coordinate. Here g(r) denote of a dark energy star. Now compact objects at the cen- an arbitrary function of the radial coordinate represent- tre of galaxies contains quarks and gluons inside nucle- ing the locally measured gravitational acceleration, which ons whose energies exceed this value [13]. According to according to general convention is assumed to be positive Georgi-Glashow grand unified model nucleons can decay in case of an inward directed gravitational attraction, and by a process in which a quark decays into a positron and negative in the case an outward directed gravitational re- two antiquarks. Interestingly an excess of positrons have pulsion. Also the function m(r) denotes the gravitational been detected in the centre of galaxies which may be the mass contained within a sphere of radius r. best evidence for dark energy stars. In addition to that, We proceed now to describe the matter distribution of primordial dark energy stars can form out of fluctuations the spherical body which is anisotropic in nature, and of spacetime analogous to a quantum critical instability the energy-momentum tensor is characterized by the fol- [2].
Load more

Recommended publications
  • String Theory, QCD and Black Holes
    Black Hole Microstate Structure Fuzzballs and Firewalls Iosif Bena IPhT, CEAEA Saclay with Nick Warner, Jan deBoer, Micha Berkooz, Simon Ross, Gianguido Dall’Agata, Stefano Giusto, Masaki Shigemori, Dieter van den Bleeken, Monica Guica, Sheer El-Showk, Stanislav Kuperstein, Hagen Triendl, Bert Vercnocke, Andrea Puhm, Ref. Ares(2012)790792 - 29/06/2012 ! Department C "Grant Management" ! Mittwoch, 12. März 2014 ! Subject: Aggressive marketing from publishing houses Dear Madam, Dear Sir, The European Research Council Executive Agency (ERCEA) would like to alert you of publishing houses and online publications which try to make profit out of publishing articles, or interviewing researchers funded from the EU budget, either by the European Research Council (ERC) or by the European Commission (EC). From time to time participants in projects funded under the EU framework programmes are contacted – often by telephone - by organisations seeking payment in return for publishing information on the work being undertaken within their projects. As with "cold calling" in general, the claims and assertions made should be treated with an appropriate level of caution before a decision is made on the best course of action. These publications and their services have not been endorsed by the EC, or the ERCEA. Common tactics to secure business may include vague references to high-level contributions from decision makers, or making the project participant believe that his or her activities have been identified on the basis of special merit which may not be the case. Commercial entities use many ways of promoting their services, but grant-holders are not obliged to use them. Whatever the impression given by such service providers, their products have not received any formal approval or endorsement from the EC or the ERCEA.
    [Show full text]
  • Exotic Compact Objects Interacting with Fundamental Fields Engineering
    Exotic compact objects interacting with fundamental fields Nuno André Moreira Santos Thesis to obtain the Master of Science Degree in Engineering Physics Supervisors: Prof. Dr. Carlos Alberto Ruivo Herdeiro Prof. Dr. Vítor Manuel dos Santos Cardoso Examination Committee Chairperson: Prof. Dr. José Pizarro de Sande e Lemos Supervisor: Prof. Dr. Carlos Alberto Ruivo Herdeiro Member of the Committee: Dr. Miguel Rodrigues Zilhão Nogueira October 2018 Resumo A astronomia de ondas gravitacionais apresenta-se como uma nova forma de testar os fundamentos da física − e, em particular, a gravidade. Os detetores de ondas gravitacionais por interferometria laser permitirão compreender melhor ou até esclarecer questões de longa data que continuam por responder, como seja a existência de buracos negros. Pese embora o número cumulativo de argumentos teóricos e evidências observacionais que tem vindo a fortalecer a hipótese da sua existência, não há ainda qualquer prova conclusiva. Os dados atualmente disponíveis não descartam a possibilidade de outros objetos exóticos, que não buracos negros, se formarem em resultado do colapso gravitacional de uma estrela suficientemente massiva. De facto, acredita-se que a assinatura do objeto exótico remanescente da coalescência de um sistema binário de objetos compactos pode estar encriptada na amplitude da onda gravitacional emitida durante a fase de oscilações amortecidas, o que tornaria possível a distinção entre buracos negros e outros objetos exóticos. Esta dissertação explora aspetos clássicos da fenomenologia de perturbações escalares e eletromagnéticas de duas famílias de objetos exóticos cuja geometria, apesar de semelhante à de um buraco negro de Kerr, é definida por uma superfície refletora, e não por um horizonte de eventos.
    [Show full text]
  • SNOWMASS21-TF1 TF0-057.Pdf 409.50KB 2020-08-31 21:46:42
    Snowmass2021 - Letter of Interest Peering inside Black Holes with Gravitational Waves Thematic Areas: (TF01) String theory, quantum gravity, black holes (TF2) Effective field theory techniques (TF3) CFT and formal QFT (TF4) Scattering amplitudes (TF5) Lattice gauge theory (TF6) Theory techniques for precision physics (TF7) Collider phenomenology (TF8) BSM model building (TF9) Astro-particle physics & cosmology (TF10) Quantum Information Science (TF11) Theory of neutrino physics (CF6) Dark Energy and Cosmic Acceleration: Complementarity of Probes and New Facilities (CF7) Cosmic Probes of Fundamental Physics Contact Information: Emil Mottola (Los Alamos National Laboratory & Perimeter Institute)[[email protected]] Author: Emil Mottola Abstract: In classical General Relativity (GR) the interiors of Black Holes (BHs) are not only singular but, if rotating, also admit closed timelike curves, violating causality.1 This feature occurs at macroscopic distance scales, far larger than the microscopic Planck scale LP l. When quantum effects are considered, severe conflicts with statistical thermodynamics, conservation of probability and an enormous BH entropy arise also at the macroscopic horizon scale.2,3 This suggests that a low energy semi-classical Effective Field Theory (EFT) approach should be applicable. In this LOI such an approach based the conformal anomaly is proposed, which leads to a non-singular horizonless, but ultra-compact object called a gravitational condensate star. The gravastar hypothesis can be tested by searching for discrete surface modes and GW echoes emitted after binary merger events. In this new era of GW and multi-messenger astronomy with additional GW detectors coming online in this decade, the time is now ripe for a full-fledged effort to confront these theoretical ideas with the observational data that hold the promise of resolving the conundrum that BHs pose, and potentially point to a new path to ultimate synthesis of gravitation and quantum theory.
    [Show full text]
  • Arxiv:2010.05354V1 [Gr-Qc] 11 Oct 2020
    Black hole or Gravastar? The GW190521 case I. Antoniou1, ∗ 1Department of Physics, University of Ioannina, GR-45110, Ioannina, Greece (Dated: August 31, 2021) The existence of cosmological compact objects with very strong gravity is a prediction of General Relativity and an exact solution of the Einstein equations. These objects are called black holes and recently we had the first observations of them. However, the theory of black hole formation has some disadvantages. In order to avoid these, some scientists suggest the existence of gravastars (gravitation vacuum stars), an alternative stellar model which seems to solve the problems of the black hole theory. In this work we compare black holes and gravastars using a wide range of the literature and we emphasize the properties of gravastars, which are consistent with the current cosmological observations. Also, we propose gravastars as the solution of the ”pair-instability” effect and a possible explanation for the observed masses of the compact objects, before the collapse, from the gravitational signal GW190521, since in the formation of a gravastar there aren’t mass restrictions. PACS numbers: 98.62.Ai, 04.20.Cv, 04.30.-w I. INTRODUCTION black holes, or some other compact object with very strong gravity. Many scientists dispute the One of the most attractive concepts in Gen- existence of black holes because if we take into ac- eral Relativity is the existence and the properties count quantum effects, the gravitational collapse of black holes, a region of spacetime where grav- of objects comes to a halt and furthermore no ity is so strong that nothing, no particles or even event horizon forms [2].
    [Show full text]
  • Arxiv:1607.03593V1 [Gr-Qc] 13 Jul 2016 Hc Ssilukona Ula N H Super-Nuclear the to and Core, Nuclear Used Densities
    Tidal deformability and I-Love-Q relations for gravastars with polytropic thin shells 1,2 3 † 4,5‡ Nami Uchikata ,∗ Shijun Yoshida , and Paolo Pani 1Department of Physics, Rikkyo University, Nishi-ikebukuro, Toshima-ku, Tokyo 171-8501, Japan 2Department of Mathematics and Physics, Graduate School of Science, Osaka City University, Sumiyoshi-ku, Osaka 558-8585, Japan 3Astronomical Institute, Tohoku University, Aramaki-Aoba, Aoba-ku, Sendai 980-8578, Japan 4Dipartimento di Fisica, ”Sapienza” Universit`adi Roma & Sezione INFN Roma1, Piazzale Aldo Moro 5, 00185 Roma, Italy 5Centro Multidisciplinar de Astrof´ısica — CENTRA, Departamento de F´ısica, Instituto Superior T´ecnico — IST, Universidade de Lisboa - UL, Av. Rovisco Pais 1, 1049-001 Lisboa, Portugal (Dated: July 14, 2016) The moment of inertia, the spin-induced quadrupole moment, and the tidal Love number of neutron-star and quark-star models are related through some relations which depend only mildly on the stellar equation of state. These “I-Love-Q” relations have important implications for astro- physics and gravitational-wave astronomy. An interesting problem is whether similar relations hold for other compact objects and how they approach the black-hole limit. To answer these questions, here we investigate the deformation properties of a large class of thin-shell gravastars, which are exotic compact objects that do not possess an event horizon nor a spacetime singularity. Working in a small-spin and small-tidal field expansion, we calculate the moment of inertia, the quadrupole moment, and the (quadrupolar electric) tidal Love number of gravastars with a polytropic thin shell. The I-Love-Q relations of a thin-shell gravastar are drastically different from those of an ordinary neu- tron star.
    [Show full text]
  • Isotropic Gravastar Model in Rastall Gravity
    Hindawi Advances in Astronomy Volume 2020, Article ID 8861168, 10 pages https://doi.org/10.1155/2020/8861168 Research Article Isotropic Gravastar Model in Rastall Gravity G. Abbas and K. Majeed Department of Mathematics, e Islamia University of Bahawalpur, Bahawalpur, Pakistan Correspondence should be addressed to G. Abbas; [email protected] Received 26 September 2020; Revised 28 October 2020; Accepted 4 November 2020; Published 16 November 2020 Academic Editor: Yu Liu Copyright © 2020 G. Abbas and K. Majeed. ,is is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. In the present paper, we have introduced a new model of gravastar with an isotropic matter distribution in Rastall gravity by the Mazur–Mottola (2004) mechanism. Mazur–Mottola approach is about the construction of gravastar which is predicted as an alternative to black hole. By following this convention, we define gravastar in the form of three phases. ,e first one is an interior phase which has negative density; the second part consists of thin shell comprising ultrarelativistic stiff fluid for which we have discussed the length, energy, and entropy. By the graphical analysis of entropy, we have shown that our proposed thin shell gravastar model is potentially stable. ,e third phase of gravastar is defined by the exterior Schwarzschild geometry. For the interior of gravastar, we have found the analytical solutions free from any singularity and the event horizon in the framework of Rastall gravity. 1. Introduction For the very first time, in the 18th century, Laplace and It was required to formulate such an alternative system Michell gave the clues of existence of a celestial body having that could tackle the abovementioned challenges; then, in extreme density and strongest gravitational effect enough 2001, Mazur and Mottola [10, 11] suggested a marvelous idea that even the light cannot be escaped.
    [Show full text]
  • The Unique Potential of Extreme Mass-Ratio Inspirals for Gravitational-Wave Astronomy 1, 2 3, 4 Christopher P
    Main Thematic Area: Formation and Evolution of Compact Objects Secondary Thematic Areas: Cosmology and Fundamental Physics, Galaxy Evolution Astro2020 Science White Paper: The unique potential of extreme mass-ratio inspirals for gravitational-wave astronomy 1, 2 3, 4 Christopher P. L. Berry, ∗ Scott A. Hughes, Carlos F. Sopuerta, Alvin J. K. Chua,5 Anna Heffernan,6 Kelly Holley-Bockelmann,7 Deyan P. Mihaylov,8 M. Coleman Miller,9 and Alberto Sesana10, 11 1CIERA, Northwestern University, 2145 Sheridan Road, Evanston, IL 60208, USA 2Department of Physics and MIT Kavli Institute, Massachusetts Institute of Technology, Cambridge, MA 02139, USA 3Institut de Ciencies` de l’Espai (ICE, CSIC), Campus UAB, Carrer de Can Magrans s/n, 08193 Cerdanyola del Valles,` Spain 4Institut d’Estudis Espacials de Catalunya (IEEC), Edifici Nexus I, Carrer del Gran Capita` 2-4, despatx 201, 08034 Barcelona, Spain 5Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109, USA 6School of Mathematics and Statistics, University College Dublin, Belfield, Dublin 4, Ireland 7Department of Physics and Astronomy, Vanderbilt University and Fisk University, Nashville, TN 37235, USA 8Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge, CB3 0HA, UK 9Department of Astronomy and Joint Space-Science Institute, University of Maryland, College Park, MD 20742-2421, USA 10School of Physics & Astronomy and Institute for Gravitational Wave Astronomy, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK 11Universita` di Milano Bicocca, Dipartimento di Fisica G. Occhialini, Piazza della Scienza 3, I-20126, Milano, Italy (Dated: March 7, 2019) The inspiral of a stellar-mass compact object into a massive ( 104–107M ) black hole ∼ produces an intricate gravitational-wave signal.
    [Show full text]
  • Table of Contents (Print)
    PHYSICAL REVIEW D PERIODICALS For editorial and subscription correspondence, Postmaster send address changes to: please see inside front cover (ISSN: 1550-7998) APS Subscription Services P.O. Box 41 Annapolis Junction, MD 20701 THIRD SERIES, VOLUME 102, NUMBER 2 CONTENTS D15 JULY 2020 The Table of Contents is a total listing of Parts A, B and C. Part A consists of articles 020001–023528, Part B articles 023529–024061, and Part C articles 024062–029902(E) PART A EDITORIALS Editorial: The Future of Physical Review D (1 pages) .............................................................................. 020001 Mirjam Cvetič RAPID COMMUNICATIONS Universal upper bound on the inflationary energy scale from the trans-Planckian censorship conjecture (7 pages) ...... 021301(R) Shuntaro Mizuno (水野俊太郎), Shinji Mukohyama (向山信治), Shi Pi (皮石), and Yun-Long Zhang (张云龙) Shift-symmetric orbital inflation: Single field or multifield? (6 pages) ........................................................... 021302(R) Ana Achúcarro, Edmund J. Copeland, Oksana Iarygina, Gonzalo A. Palma, Dong-Gang Wang, and Yvette Welling Constraint on the Yukawa suppression of the Newtonian potential from the planetary ephemeris INPOP19a (6 pages) 021501(R) L. Bernus, O. Minazzoli, A. Fienga, M. Gastineau, J. Laskar, P. Deram, and A. Di Ruscio Testing Brans-Dicke gravity with screening by scalar gravitational wave memory (6 pages) ................................ 021502(R) Kazuya Koyama Lightcone commutator and stress-tensor exchange in d>2 conformal field theories (6 pages) ............................. 021701(R) Kuo-Wei Huang ARTICLES Detection of cosmic structures using the bispectrum phase. I. Mathematical foundations (24 pages) ....................... 022001 Nithyanandan Thyagarajan and Chris L. Carilli Detection of cosmic structures using the bispectrum phase. II. First results from application to cosmic reionization using the Hydrogen Epoch of Reionization Array (19 pages) .................................................................
    [Show full text]
  • How to Tell a Gravastar from a Black Hole
    IOP PUBLISHING CLASSICAL AND QUANTUM GRAVITY Class. Quantum Grav. 24 (2007) 4191–4206 doi:10.1088/0264-9381/24/16/013 How to tell a gravastar from a black hole Cecilia B M H Chirenti1,2 and Luciano Rezzolla2,3 1 Instituto de F´ısica, Universidade de Sao˜ Paulo, Sao˜ Paulo, Brazil 2 Max-Planck-Institut fur¨ Gravitationsphysik, Albert Einstein Institut, 14476 Golm, Germany 3 Department of Physics, Louisiana State University, Baton Rouge, LA 70803, USA Received 11 June 2007, in final form 29 June 2007 Published 31 July 2007 Online at stacks.iop.org/CQG/24/4191 Abstract Gravastars have been recently proposed as potential alternatives to explain the astrophysical phenomenology traditionally associated with black holes, raising the question of whether the two objects can be distinguished at all. Leaving aside the debate about the processes that would lead to the formation of a gravastar and the astronomical evidence in their support, here we address two basic questions: is a gravastar stable against generic perturbations? If it is stable, can an observer distinguish it from a black hole of the same mass? To answer these questions we construct a general class of gravastars and determine the conditions they must satisfy in order to exist as equilibrium solutions of the Einstein equations. For such models we perform a systematic stability analysis against axial perturbations, computing the real and imaginary parts of the eigenfrequencies. Overall, we find that gravastars are stable to axial perturbations, but also that their quasi-normal modes differ from those of a black hole of the same mass and thus can be used to discern, beyond dispute, a gravastar from a black hole.
    [Show full text]
  • Astronomy February 18, 2013
    Outline of Astronomy February 18, 2013 Contents PHYS>Astronomy ............................................................................................................................................................. 1 PHYS>Astronomy>Universe ........................................................................................................................................ 2 PHYS>Astronomy>Universe>Cosmology .............................................................................................................. 5 PHYS>Astronomy>Universe>Cosmology>Energy .......................................................................................... 15 PHYS>Astronomy>Universe>Cosmology>Matter ........................................................................................... 16 PHYS>Astronomy>Universe>Cosmology>Matter>Particle ........................................................................ 17 PHYS>Astronomy>Universe>Cosmology>Radiation ...................................................................................... 17 PHYS>Astronomy>Universe>Cosmology>Singularity .................................................................................... 18 PHYS>Astronomy>Universe>Cosmology>Singularity>Black Hole ........................................................... 18 PHYS>Astronomy>Universe>Cosmology>Theories ........................................................................................ 22 PHYS>Astronomy>Universe>Cosmology>Theories>Inflation ..................................................................
    [Show full text]
  • The Digital Space Structure, Superconductor, and Superstar
    Global Journal of Science Frontier Research: A Physics and Space Science Volume 14 Issue 3 Version 1.0 Year 2014 Type : Double Blind Peer Reviewed International Research Journal Publisher: Global Journals Inc. (USA) Online ISSN: 2249-4626 & Print ISSN: 0975-5896 The Digital Space Structure, Superconductor, and Superstar By Ding-Yu Chung Abstract- In the digital space structure, space is digitalized by 1 and 0 for attachment space and detachment space, respectively. A special force field (the short-range extreme force field) can be derived from the digital space structure to generate superconductor at extremely low temperature and superstar at extremely high density. Singularity-free superstar is a model for the collapse of large stars and for GRBs, and as an alternative to black hole. Attachment space allows object to attach to account for rest mass and reversible movement, while detachment space allows no object to attach to account for irreversible kinetic energy. The combination of attachment space and detachment space brings about the three structures: binary partition space, miscible space, orbinary lattice space. Binary partition space (1)n(0)n consists of separated continuous phases of attachment space and detachment space to account for quantum mechanics and extreme force field. In miscible space (1+0)n, attachment space is miscible to detachment space without separation to account for special relativity. Keywords: space structure, quantum mechanics, force fields, superconductor, superstar, black hole, gravastar, GRB, collapsar, singularity. GJSFR-A Classification : FOR Code: 240203p TheDigitalSpaceStructureSuperconductorandSuperstar Strictly as per the compliance and regulations of : © 2014. Ding-Yu Chung. This is a research/review paper, distributed under the terms of the Creative Commons Attribution- Noncommercial 3.0 Unported License http://creativecommons.org/licenses/by-nc/3.0/), permitting all non commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
    [Show full text]
  • Approximate Universal Relations for Neutron Stars and Quark Stars
    Approximate universal relations for neutron stars and quark stars Authors: Kent Yagi and Nicolas Yunes NOTICE: this is the author’s version of a work that was accepted for publication in Physics Reports. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Physics Reports, VOL# 681, (March 2017). DOI# 10.1016/j.physrep.2017.03.002 Yagi, Kent , and Nicolas Yunes. "Approximate universal relations for neutron stars and quark stars." Physics Reports (March 2017). DOI: 10.1016/j.physrep.2017.03.002. Made available through Montana State University’s ScholarWorks scholarworks.montana.edu Approximate universal relations for neutron stars and quark stars Kent Yagi a,b,*, Nicolás Yunes b a Department of Physics, Princeton University, Princeton, NJ 08544, USA b eXtreme Gravity Institute, Department of Physics, Montana State University, Bozeman, MT 59717, USA Abstract Neutron stars and quark stars are ideal laboratories to study fundamental physics at supra nuclear densities and strong gravitational fields. Astrophysical observables, however, depend strongly on the star's internal structure, which is currently unknown due to uncertainties in the equation of state. Universal relations, however, exist among certain stellar observables that do not depend sensitively on the star's internal structure. One such set of relations is between the star's moment of inertia (I), its tidal Love number (Love) and its quadrupole moment (Q ), the so-called I–Love–Q relations.
    [Show full text]