14,184 research outputs found
Domain Wall Bubbles in High Energy Heavy Ion Collisions
It has been recently shown that meta-stable domain walls exist in
high-density QCD () as well as in QCD with large number of colors
(), with the lifetime being exponentially long in both cases.
Such metastable domain walls may exist in our world as well, especially in hot
hadronic matter with temperature close to critical. In this paper we discuss
what happens if a bubble made of such wall is created in heavy ion collisions,
in the mixed phase between QGP and hadronic matter. We show it will further be
expanded to larger volume by the pion pressure, before it
disappears, either by puncture or contraction. Both scenarios leave distinctive
experimental signatures of such events, negatively affecting the interference
correlations between the outgoing pions.Comment: 6 pages, 1 fi
Observing Spontaneous Strong Parity Violation in Heavy-Ion Collisions
We discuss the problem of observing spontaneous parity and CP violation in
collision systems. We discuss and propose observables which may be used in
heavy-ion collisions to observe such violations, as well as event-by-event
methods to analyze the data. Finally, we discuss simple monte-carlo models of
these CP violating effects which we have used to develop our techniques and
from which we derive rough estimates of sensitivities to signals which may be
seen at RHIC
Inverse scattering approach to multiwavelength Fabry-PĂ©rot laser design
A class of multiwavelength Fabry-Pérot lasers is introduced where the spectrum is tailored through a patterning of the cavity effective index. The cavity geometry is obtained using an inverse scattering approach and can be designed such that the spacing of discrete Fabry-Pérot lasing modes is limited only by the bandwidth of the inverted gain medium. A specific two-color semiconductor laser with a mode spacing in the THz region is designed, and measurements are presented demonstrating the simultaneous oscillation of the two wavelengths. The nonperiodic effective index profile of the particular two-color device considered is shown to be related to a Moiré or superstructure grating
The networked seceder model: Group formation in social and economic systems
The seceder model illustrates how the desire to be different than the average
can lead to formation of groups in a population. We turn the original, agent
based, seceder model into a model of network evolution. We find that the
structural characteristics our model closely matches empirical social networks.
Statistics for the dynamics of group formation are also given. Extensions of
the model to networks of companies are also discussed
Optical Follow-up of New SMC Wing Be/X-ray Binaries
We investigate the optical counterparts of recently discovered Be/X-ray
binaries in the Small Magellanic Cloud. In total four sources, SXP101, SXP700,
SXP348 and SXP65.8 were detected during the Chandra Survey of the Wing of the
SMC. SXP700 and SXP65.8 were previously unknown. Many optical ground based
telescopes have been utilised in the optical follow-up, providing coverage in
both the red and blue bands. This has led to the classification of all of the
counterparts as Be stars and confirms that three lie within the Galactic
spectral distribution of known Be/X-ray binaries. SXP101 lies outside this
distribution becoming the latest spectral type known. Monitoring of the Halpha
emission line suggests that all the sources bar SXP700 have highly variable
circumstellar disks, possibly a result of their comparatively short orbital
periods. Phase resolved X-ray spectroscopy has also been performed on SXP65.8,
revealing that the emission is indeed harder during the passage of the X-ray
beam through the line of sight.Comment: 9 pages, 9 figures, 2 tables, accepted for publication in MNRA
Can Induced Theta Vacua be Created in Heavy Ion Collisions?
The development of the early Universe is a remarkable laboratory for the
study of most nontrivial properties of particle physics. What is more
remarkable is the fact that these phenomena at the QCD scale can be, in
principle, experimentally tested in heavy ion collisions. We expect that, in
general, an arbitrary theta-state would be created in the heavy ion collisions,
similar to the creation of the disoriented chiral condensate with an arbitrary
isospin direction. It should be a large domain with a wrong
orientation. We test this idea numerically in a simple model where we study the
evolution of the phases of the chiral condensates in QCD with two quark flavors
with non-zero theta-parameter. We see the formation of a non-zero theta-vacuum
with the formation time of the order of seconds. This result will
have important implications for a possible axion search experiment at RHIC.Comment: 4 pages, 3 figures, Latex, Discussion of experimental signatures
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