41 research outputs found
Late-time Phase transition and the Galactic halo as a Bose Liquid: (II) the Effect of Visible Matter
In the previous work, we investigated the rotation curves of galaxies
assuming that the dark matter consists of ultra light boson appearing in
late time phase transition' theory. Generalizing this work, we consider the
effect of visible matter and classify the types of rotation curves as we vary
the fraction of the mass and extention of visible matter. We show that visible
matter, in galaxies with flat rotation curves, has mass fraction and it is confined within the distance fraction .Comment: 10 pages, 10 figures included, to appear in Phys. Rev. D50,p365
The Super W_\INFTY Symmetry of the Manin-Radul Super KP Hierarchy
We show that the Manin-Radul super KP hierarchy is invariant under super
W_\infty transformations. These transformations are characterized by time
dependent flows which commute with the usual flows generated by the conserved
quantities of the super KP hierarchy.Comment: (12 pages
Augmented Reality in Astrophysics
Augmented Reality consists of merging live images with virtual layers of
information. The rapid growth in the popularity of smartphones and tablets over
recent years has provided a large base of potential users of Augmented Reality
technology, and virtual layers of information can now be attached to a wide
variety of physical objects. In this article, we explore the potential of
Augmented Reality for astrophysical research with two distinct experiments: (1)
Augmented Posters and (2) Augmented Articles. We demonstrate that the emerging
technology of Augmented Reality can already be used and implemented without
expert knowledge using currently available apps. Our experiments highlight the
potential of Augmented Reality to improve the communication of scientific
results in the field of astrophysics. We also present feedback gathered from
the Australian astrophysics community that reveals evidence of some interest in
this technology by astronomers who experimented with Augmented Posters. In
addition, we discuss possible future trends for Augmented Reality applications
in astrophysics, and explore the current limitations associated with the
technology. This Augmented Article, the first of its kind, is designed to allow
the reader to directly experiment with this technology.Comment: 15 pages, 11 figures. Accepted for publication in Ap&SS. The final
publication will be available at link.springer.co
Drag force in SYM plasma with B field from AdS/CFT
We investigate drag force in a thermal plasma of N=4 super Yang-Mills theory
via both fundamental and Dirichlet strings under the influence of non-zero NSNS
-field background. In the description of AdS/CFT correspondence the endpoint
of these strings correspondes to an external monopole or quark moving with a
constant electromagnetic field. We demonstrate how the configuration of string
tail as well as the drag force obtains corrections in this background.Comment: 13 pages, 2 figures, more discussion and reference adde
Minimum mass of galaxies from BEC or scalar field dark matter
Many problems of cold dark matter models such as the cusp problem and the
missing satellite problem can be alleviated, if galactic halo dark matter
particles are ultra-light scalar particles and in Bose-Einstein condensate
(BEC), thanks to a characteristic length scale of the particles. We show that
this finite length scale of the dark matter can also explain the recently
observed common central mass of the Milky Way satellites ()
independent of their luminosity, if the mass of the dark matter particle is
about .Comment: 10 pages, 1 figure, accepted in JCA
Newtonian Collapse of Scalar Field Dark Matter
In this letter, we develop a Newtonian approach to the collapse of galaxy
fluctuations of scalar field dark matter under initial conditions inferred from
simple assumptions. The full relativistic system, the so called
Einstein-Klein-Gordon, is reduced to the Schr\"odinger-Newton one in the weak
field limit. The scaling symmetries of the SN equations are exploited to track
the non-linear collapse of single scalar matter fluctuations. The results can
be applied to both real and complex scalar fields.Comment: 4 pages RevTex4 file, 4 eps figure
Evolution of the Schr\"odinger--Newton system for a self--gravitating scalar field
Using numerical techniques, we study the collapse of a scalar field
configuration in the Newtonian limit of the spherically symmetric
Einstein--Klein--Gordon (EKG) system, which results in the so called
Schr\"odinger--Newton (SN) set of equations. We present the numerical code
developed to evolve the SN system and topics related, like equilibrium
configurations and boundary conditions. Also, we analyze the evolution of
different initial configurations and the physical quantities associated to
them. In particular, we readdress the issue of the gravitational cooling
mechanism for Newtonian systems and find that all systems settle down onto a
0--node equilibrium configuration.Comment: RevTex file, 19 pages, 26 eps figures. Minor changes, matches version
to appear in PR
Improved Holographic QCD
We provide a review to holographic models based on Einstein-dilaton gravity
with a potential in 5 dimensions. Such theories, for a judicious choice of
potential are very close to the physics of large-N YM theory both at zero and
finite temperature. The zero temperature glueball spectra as well as their
finite temperature thermodynamic functions compare well with lattice data. The
model can be used to calculate transport coefficients, like bulk viscosity, the
drag force and jet quenching parameters, relevant for the physics of the
Quark-Gluon Plasma.Comment: LatEX, 65 pages, 28 figures, 9 Tables. Based on lectures given at
several Schools. To appear in the proceedinds of the 5th Aegean School
(Milos, Greece
Parton energy loss at strong coupling and the universal bound
The apparent universality of jet quenching observed in heavy ion collisions
at RHIC for light and heavy quarks, as well as for quarks and gluons, is very
puzzling and calls for a theoretical explanation. Recently it has been proposed
that the synchrotron--like radiation at strong coupling gives rise to a
universal bound on the energy of a parton escaping from the medium. Since this
bound appears quite low, almost all of the observed particles at high
transverse momentum have to originate from the surface of the hot fireball.
Here I make a first attempt of checking this scenario against the RHIC data and
formulate a "Universal Bound Model" of jet quenching that can be further tested
at RHIC and LHC.Comment: 8 pages, 2 figures, invited plenary talk given at "Hard Probes 2008"
Conference, 8-14 June 2008, Illa da Toxa, Galicia, Spai
The dynamics of quark-gluon plasma and AdS/CFT
In these pedagogical lectures, we present the techniques of the AdS/CFT
correspondence which can be applied to the study of real time dynamics of a
strongly coupled plasma system. These methods are based on solving
gravitational Einstein's equations on the string/gravity side of the AdS/CFT
correspondence. We illustrate these techniques with applications to the
boost-invariant expansion of a plasma system. We emphasize the common
underlying AdS/CFT description both in the large proper time regime where
hydrodynamic dynamics dominates, and in the small proper time regime where the
dynamics is far from equilibrium. These AdS/CFT methods provide a fascinating
arena interrelating General Relativity phenomenae with strongly coupled gauge
theory physics.Comment: 35 pages, 3 figures. Lectures at the 5th Aegean summer school, `From
gravity to thermal gauge theories: the AdS/CFT correspondence'. To appear in
the proceedings in `Lecture Notes in Physics