388 research outputs found
Scalar field theory on -Minkowski space-time and Doubly Special Relativity
In this paper we recall the construction of scalar field action on
-Minkowski space-time and investigate its properties. In particular we
show how the co-product of -Poincar\'e algebra of symmetries arises
from the analysis of the symmetries of the action, expressed in terms of
Fourier transformed fields. We also derive the action on commuting space-time,
equivalent to the original one. Adding the self-interaction term we
investigate the modified conservation laws. We show that the local interactions
on -Minkowski space-time give rise to 6 inequivalent ways in which
energy and momentum can be conserved at four-point vertex. We discuss the
relevance of these results for Doubly Special Relativity.Comment: 17 pages; some editing done, final version to be published in Int. J.
Mod. Phys.
Some Pattern Recognition Challenges in Data-Intensive Astronomy
We review some of the recent developments and challenges posed by the data
analysis in modern digital sky surveys, which are representative of the
information-rich astronomy in the context of Virtual Observatory. Illustrative
examples include the problems of an automated star-galaxy classification in
complex and heterogeneous panoramic imaging data sets, and an automated,
iterative, dynamical classification of transient events detected in synoptic
sky surveys. These problems offer good opportunities for productive
collaborations between astronomers and applied computer scientists and
statisticians, and are representative of the kind of challenges now present in
all data-intensive fields. We discuss briefly some emergent types of scalable
scientific data analysis systems with a broad applicability.Comment: 8 pages, compressed pdf file, figures downgraded in quality in order
to match the arXiv size limi
Discovery of a Probable Physical Triple Quasar
We report the discovery of the first known probable case of a physical triple
quasar (not a gravitational lens). A previously known double system, QQ
1429-008 at z = 2.076, is shown to contain a third, fainter QSO component at
the same redshift within the measurement errors. Deep optical and IR imaging at
the Keck and VLT telescopes has failed to reveal a plausible lensing galaxy
group or a cluster, and moreover, we are unable to construct any viable lensing
model which could lead to the observed distribution of source positions and
relative intensities of the three QSO image components. Furthermore, there are
hints of differences in broad-band spectral energy distributions of different
components, which are more naturally understood if they are physically distinct
AGN. Therefore, we conclude that this system is most likely a physical triple
quasar, the first such close QSO grouping known at any redshift. The projected
component separations in the restframe are ~ 30 - 50 kpc for the standard
concordance cosmology, typical of interacting galaxy systems. The existence of
this highly unusual system supports the standard picture in which galaxy
interactions lead to the onset of QSO activity.Comment: Submitted to ApJL, LaTeX, 13 pages, 4 eps figures, all include
2+1 gravity and Doubly Special Relativity
It is shown that gravity in 2+1 dimensions coupled to point particles
provides a nontrivial example of Doubly Special Relativity (DSR). This result
is obtained by interpretation of previous results in the field and by
exhibiting an explicit transformation between the phase space algebra for one
particle in 2+1 gravity found by Matschull and Welling and the corresponding
DSR algebra. The identification of 2+1 gravity as a system answers a
number of questions concerning the latter, and resolves the ambiguity of the
basis of the algebra of observables.
Based on this observation a heuristic argument is made that the algebra of
symmetries of ultra high energy particle kinematics in 3+1 dimensions is
described by some DSR theory.Comment: 8 pages Latex, no figures, typos correcte
Deformed Special Relativity and Deformed Symmetries in a Canonical Framework
In this paper we have studied the nature of kinematical and dynamical laws in
-Minkowski spacetime from a new perspective: the canonical phase space
approach. We discuss a particular form of -Minkowski phase space
algebra that yields the -extended finite Lorentz transformations
derived in \cite{kim}. This is a particular form of a Deformed Special
Relativity model that admits a modified energy-momentum dispersion law as well
as noncommutative -Minkowski phase space. We show that this system can
be completely mapped to a set of phase space variables that obey canonical (and
{\it{not}} -Minkowski) phase space algebra and Special Relativity
Lorentz transformation (and {\it{not}} -extended Lorentz
transformation). The complete set of deformed symmetry generators are
constructed that obeys an unmodified closed algebra but induce deformations in
the symmetry transformations of the physical -Minkowski phase space
variables. Furthermore, we demonstrate the usefulness and simplicity of this
approach through a number of phenomenological applications both in classical
and quantum mechanics. We also construct a Lagrangian for the
-particle.Comment: Revised version with change in Title and Abstract, No change in
mathematical content, Reference section enlarged, Discussion on Soccer Ball
Problem removed; Version to appear in PR
Relative Locality in -Poincar\'e
We show that the -Poincar\'e Hopf algebra can be interpreted in the
framework of curved momentum space leading to the relativity of locality
\cite{AFKS}. We study the geometric properties of the momentum space described
by -Poincar\'e, and derive the consequences for particles propagation
and energy-momentum conservation laws in interaction vertices, obtaining for
the first time a coherent and fully workable model of the deformed relativistic
kinematics implied by -Poincar\'e. We describe the action of boost
transformations on multi-particles systems, showing that in order to keep
covariant the composed momenta it is necessary to introduce a dependence of the
rapidity parameter on the particles momenta themselves. Finally, we show that
this particular form of the boost transformations keeps the validity of the
relativity principle, demonstrating the invariance of the equations of motion
under boost transformations.Comment: 24 pages, 4 figures, 1 table. v2 matches accepted CQG versio
Doubly Special Relativity and de Sitter space
In this paper we recall the construction of Doubly Special Relativity (DSR)
as a theory with energy-momentum space being the four dimensional de Sitter
space. Then the bases of the DSR theory can be understood as different
coordinate systems on this space. We investigate the emerging geometrical
picture of Doubly Special Relativity by presenting the basis independent
features of DSR that include the non-commutative structure of space-time and
the phase space algebra. Next we investigate the relation between our geometric
formulation and the one based on quantum -deformations of the
Poincar\'e algebra. Finally we re-derive the five-dimensional differential
calculus using the geometric method, and use it to write down the deformed
Klein-Gordon equation and to analyze its plane wave solutions.Comment: 26 pages, one formula (67) corrected; some remarks adde
Kinematics of a relativistic particle with de Sitter momentum space
We discuss kinematical properties of a free relativistic particle with
deformed phase space in which momentum space is given by (a submanifold of) de
Sitter space. We provide a detailed derivation of the action, Hamiltonian
structure and equations of motion for such free particle. We study the action
of deformed relativistic symmetries on the phase space and derive explicit
formulas for the action of the deformed Poincare' group. Finally we provide a
discussion on parametrization of the particle worldlines stressing analogies
and differences with ordinary relativistic kinematics.Comment: RevTeX, 12 pages, no figure
The Free Particle in Deformed Special Relativity
The phase space of a classical particle in DSR contains de Sitter space as
the space of momenta. We start from the standard relativistic particle in five
dimensions with an extra constraint and reduce it to four dimensional DSR by
imposing appropriate gauge fixing. We analyze some physical properties of the
resulting theories like the equations of motion, the form of Lorentz
transformations and the issue of velocity. We also address the problem of the
origin and interpretation of different bases in DSR.Comment: 15 page
New approaches to object classification in synoptic sky surveys
Digital synoptic sky surveys pose several new object classification challenges. In surveys where real-time detection and classification of transient events is a science driver, there is a need for an effective elimination of instrument-related artifacts which can masquerade as transient sources in the detection pipeline, e.g., unremoved large cosmic rays, saturation trails, reflections, crosstalk artifacts, etc. We have implemented such an Artifact Filter, using a supervised neural network,
for the real-time processing pipeline in the Palomar-Quest (PQ) survey. After the training phase, for each object it takes as input a set of measured morphological parameters and returns the probability of it being a real object. Despite the relatively low number of training cases for many kinds of artifacts, the overall artifact classification rate is around 90%, with no genuine transients misclassified during our real-time scans. Another question is how to assign an optimal star-galaxy
classification in a multi-pass survey, where seeing and other conditions change between different epochs, potentially producing inconsistent classifications for the same object. We have implemented a star/galaxy multipass classifier that makes use of external and a priori knowledge to find the optimal classification from the individually derived ones. Both these techniques can be applied to other, similar surveys and data sets
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