931 research outputs found
Rotating Black Hole Thermodynamics with a Particle Probe
The thermodynamics of Myers-Perry black holes in general dimensions are
studied using a particle probe. When undergoing particle absorption, the
changes of the entropy and irreducible mass are shown to be dependent on the
particle radial momentum. The black hole thermodynamic behaviors are dependent
on dimensionality for specific rotations. For a 4-dimensional Kerr black hole,
its black hole properties are maintained for any particle absorption.
5-dimensional black holes can avoid a naked ring singularity by absorbing a
particle in specific momenta ranges. Black holes over 6 dimensions become
ultra-spinning black holes through a specific form of particle absorption. The
microscopical changes are interpreted in limited cases of Myers-Perry black
holes using Kerr/CFT correspondence. We systematically describe the black hole
properties changed by particle absorption in all dimensions.Comment: 14 page
Geodesic motions in extraordinary string geometry
The geodesic properties of the extraordinary vacuum string solution in (4+1)
dimensions are analyzed by using Hamilton-Jacobi method. The geodesic motions
show distinct properties from those of the static one. Especially, any freely
falling particle can not arrive at the horizon or singularity. There exist
stable null circular orbits and bouncing timelike and null geodesics. To get
into the horizon {or singularity}, a particle need to follow a non-geodesic
trajectory. We also analyze the orbit precession to show that the precession
angle has distinct features for each geometry such as naked singularity, black
string, and wormhole.Comment: 15 pages, 11 figure
Horava-Lifshitz gravity: tighter constraints for the Kehagias-Sfetsos solution from new solar system data
We analytically work out the perturbation induced by the Kehagias-Sfetsos
(KS) space-time solution of the Horava-Lifshitz (HL) modified gravity at long
distances on the two-body range for a pair of test particles A and B orbiting
the same mass M. We apply our results to the most recently obtained
range-residuals \delta\rho for some planets of the solar system (Mercury, Mars,
Saturn) ranged from the Earth to effectively constrain the dimensionsless KS
parameter \psi_0 for the Sun. We obtain \psi_0 >= 7.2 x 10^-10 (Mercury),
\psi_0 >= 9 x 10^-12 (Mars), \psi_0 >= 1.7 x 10^-12 (Saturn). Such lower bounds
are tighter than other ones existing in literature by several orders of
magnitude. We also preliminarily obtain \psi_0 >= 8 x 10^-10 for the system
constituted by the S2 star orbiting the Supermassive Black Hole (SBH) in the
center of the Galaxy.Comment: LaTex2e, 15 pages, 1 table, 3 figures, 31 references. Version
matching the one at press in International Journal of Modern Physics D
(IJMPD
Counteracting Selfish Nodes Using Reputation Based System in Mobile Ad Hoc Networks
A mobile ad hoc network (MANET) is a group of nodes constituting a network of mobile nodes without predefined and pre-established architecture where mobile nodes can communicate without any dedicated access points or base stations. In MANETs, a node may act as a host as well as a router. Nodes in the network can send and receive packets through intermediate nodes. However, the existence of malicious and selfish nodes in MANETs severely degrades network performance. The identification of such nodes in the network and their isolation from the network is a challenging problem. Therefore, in this paper, a simple reputation-based scheme is proposed which uses the consumption and contribution information for selfish node detection and cooperation enforcement. Nodes failing to cooperate are detached from the network to save resources of other nodes with good reputation. The simulation results show that our proposed scheme outperforms the benchmark scheme in terms of NRL (normalized routing load), PDF (packet delivery fraction), and packet drop in the presence of malicious and selfish attacks. Furthermore, our scheme identifies the selfish nodes quickly and accurately as compared to the benchmark scheme
Production and optical properties of liquid scintillator for the JSNS experiment
The JSNS (J-PARC Sterile Neutrino Search at J-PARC Spallation Neutron
Source) experiment will search for neutrino oscillations over a 24 m short
baseline at J-PARC. The JSNS inner detector will be filled with 17 tons
of gadolinium-loaded liquid scintillator (LS) with an additional 31 tons of
unloaded LS in the intermediate -catcher and outer veto volumes.
JSNS has chosen Linear Alkyl Benzene (LAB) as an organic solvent because
of its chemical properties. The unloaded LS was produced at a refurbished
facility, originally used for scintillator production by the RENO experiment.
JSNS plans to use ISO tanks for the storage and transportation of the LS.
In this paper, we describe the LS production, and present measurements of its
optical properties and long term stability. Our measurements show that storing
the LS in ISO tanks does not result in degradation of its optical properties.Comment: 7 pages, 4 figures
Particle Probe of Horava-Lifshitz Gravity
Kehagias-Sfetsos black hole in Ho\v{r}ava-Lifshitz gravity is probed through
particle geodesics. Gravitational force of KS black hole becomes weaker than
that of Schwarzschild around horizon and interior space. Particles can be
always scattered or trapped in new closed orbits, unlike those falling forever
in Schwarzschild black. The properties of null and timelike geodesics are
classified with values of coupling constants. The precession rates of the
orbits are evaluated. The time trajectories are also classified under different
values of coupling constants for both null and timelike geodesics. Physical
phenomena that may be observable are discussed.Comment: 10 pages, 8 figure
16-09 Transportation Mobility Among Low-Income, Transportation Disadvantaged Older Adults Living in a Low Density Urban Environment Using Innovative Data Collection Methods
This study investigates the transportation disadvantage that low-income, older adults face on an individual basis. To accomplish this, research team members custom designed an innovative âtravel diaryâ app, MyAmble, which tracks planned, completed, failed/uncompleted trips, and unserved trips in its Trip Planner module. In addition to the typical transportation planning data (e.g. origin, destination, mode), MyAmble collects data related to the completed or failed/uncompleted tripâs impact on the participantâs mood and quality of life. MyAmble utilizes 3 additional modules (Challenge Logger, Travel Buddy, and Travel History) to collect qualitative data related to the role that transportation plays in the participantâs life and history.
The field test shows significant promise in terms of capturing data on quantity and impact of missed trips, particularly as they relate to psycho-social-emotional well-being and autonomy; however, the selected population of low-income, community-dwelling older adults face health challenges that may have limited some participantsâ ability to utilize the app. The study generates critical feedback for continued improvements to MyAmble. Participants expressed positive feedback and strong support for the app, specifically the Travel Buddy feature. The data generated by MyAmble provide new insights into the challenges facing environmental justice communities
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