5,471 research outputs found
Conditions for Phase Equilibrium in Supernovae, Proto-Neutron and Neutron Stars
We investigate the qualitative properties of phase transitions in a general
way, if not the single particle numbers of the system but only some particular
charges like e.g. baryon number are conserved. In addition to globally
conserved charges we analyze the implications of locally conserved charge
fractions, like e.g. local electric charge neutrality or locally fixed proton
or lepton fractions. The conditions for phase equilibrium are derived and it is
shown, that the properties of the phase transition do not depend on the locally
conserved fractions. Finally, the general formalism is applied to the
liquid-gas phase transition and the hadron-quark phase transition for typical
astrophysical environments like in supernovae, proto-neutron or a neutron
stars. We demonstrate that the Maxwell construction known from
cold-deleptonized neutron star matter with two locally charge neutral phases
requires modifications and further assumptions concerning the applicability for
hot lepton-rich matter. All possible combinations of local and global
conservation laws are analyzed, and the physical meaningful cases are
identified. Several new kinds of mixed phases are presented, as e.g. a locally
charge neutral mixed phase in proto-neutron stars which will disappear during
the cooling and deleptonization of the proto-neutron star.Comment: 18 page
A new possible quark-hadron mixed phase in protoneutron stars
The phase transition from hadronic matter to quark matter at high density
might be a strong first order phase transition in presence of a large surface
tension between the two phases. While this implies a constant-pressure mixed
phase for cold and catalyzed matter this is not the case for the hot and lepton
rich matter formed in a protoneutron star. We show that it is possible to
obtain a mixed phase with non-constant pressure by considering the global
conservation of lepton number during the stage of neutrino trapping. In turn,
it allows for the appearance of a new kind of mixed phase as long as neutrinos
are trapped and its gradual disappearance during deleptonization. This new
mixed phase, being composed by two electric neutral phases, does not develop a
Coulomb lattice and it is formed only by spherical structures, drops and
bubbles, which can have macroscopic sizes. The disappearance of the mixed phase
at the end of deleptonization might lead to a delayed collapse of the star into
a more compact configuration containing a core of pure quark phase. In this
scenario, a significant emission of neutrinos and, possibly, gravitational
waves are expected.Comment: 4 pages, 4 figure
Mass, radius, and composition of the outer crust of nonaccreting cold neutron stars
The properties and composition of the outer crust of nonaccreting cold
neutron stars are studied by applying the model of Baym, Pethick, and
Sutherland, which was extended by including higher order corrections of the
atomic binding, screening, exchange and zero-point energy. The most recent
experimental nuclear data from the atomic mass table of Audi, Wapstra, and
Thibault from 2003 is used. Extrapolation to the drip line is utilized by
various state-of-the-art theoretical nuclear models (finite range droplet,
relativistic nuclear field and non-relativistic Skyrme Hartree-Fock
parameterizations). The different nuclear models are compared with respect to
the mass and radius of the outer crust for different neutron star
configurations and the nuclear compositions of the outer crust.Comment: 5 pages, 2 figures, submitted to J. Phys. G, part of the proceedings
of the Nuclear Physics in Astrophysics III conference in Dresde
Dynamical Systems On Three Manifolds Part II: 3-Manifolds,Heegaard Splittings and Three-Dimensional Systems
The global behaviour of nonlinear systems is extremely important in control
and systems theory since the usual local theories will only give information
about a system in some neighbourhood of an operating point. Away from that
point, the system may have totally different behaviour and so the theory
developed for the local system will be useless for the global one.
In this paper we shall consider the analytical and topological structure of
systems on 2- and 3- manifolds and show that it is possible to obtain systems
with 'arbitrarily strange' behaviour, i.e., arbitrary numbers of chaotic
regimes which are knotted and linked in arbitrary ways. We shall do this by
considering Heegaard Splittings of these manifolds and the resulting systems
defined on the boundaries.Comment: 15 pages with 9 pictures. Accepted by Int. J. of Bifurcation and
Chao
Pushing 1D CCSNe to explosions: model and SN 1987A
We report on a method, PUSH, for triggering core-collapse supernova
explosions of massive stars in spherical symmetry. We explore basic explosion
properties and calibrate PUSH such that the observables of SN1987A are
reproduced. Our simulations are based on the general relativistic hydrodynamics
code AGILE combined with the detailed neutrino transport scheme IDSA for
electron neutrinos and ALS for the muon and tau neutrinos. To trigger
explosions in the otherwise non-exploding simulations, we rely on the
neutrino-driven mechanism. The PUSH method locally increases the energy
deposition in the gain region through energy deposition by the heavy neutrino
flavors. Our setup allows us to model the explosion for several seconds after
core bounce. We explore the progenitor range 18-21M. Our studies
reveal a distinction between high compactness (HC) and low compactness (LC)
progenitor models, where LC models tend to explore earlier, with a lower
explosion energy, and with a lower remnant mass. HC models are needed to obtain
explosion energies around 1 Bethe, as observed for SN1987A. However, all the
models with sufficiently high explosion energy overproduce Ni. We
conclude that fallback is needed to reproduce the observed nucleosynthesis
yields. The nucleosynthesis yields of Ni depend sensitively on the
electron fraction and on the location of the mass cut with respect to the
initial shell structure of the progenitor star. We identify a progenitor and a
suitable set of PUSH parameters that fit the explosion properties of SN1987A
when assuming 0.1M of fallback. We predict a neutron star with a
gravitational mass of 1.50M. We find correlations between explosion
properties and the compactness of the progenitor model in the explored
progenitors. However, a more complete analysis will require the exploration of
a larger set of progenitors with PUSH.Comment: revised version as accepted by ApJ (results unchanged, text modified
for clarification, a few references added); 26 pages, 20 figure
Strange matter in core-collapse supernovae
We discuss the possible impact of strange quark matter on the evolution of
core-collapse supernovae with emphasis on low critical densities for the
quark-hadron phase transition. For such cases the hot proto-neutron star can
collapse to a more compact hybrid star configuration hundreds of milliseconds
after core-bounce. The collapse triggers the formation of a second shock wave.
The latter leads to a successful supernova explosion and leaves an imprint on
the neutrino signal. These dynamical features are discussed with respect to
their compatibility with recent neutron star mass measurements which indicate a
stiff high density nuclear matter equation of state.Comment: 8 pages, 3 figures, Invited talk at the "Strangeness in Quark Matter"
conference, 18-24 September 2011, Polish Academy of Arts and Sciences,
Cracow, Polan
Finite-size effects in dynamics of zero-range processes
The finite-size effects prominent in zero-range processes exhibiting a
condensation transition are studied by using continuous-time Monte Carlo
simulations. We observe that, well above the thermodynamic critical point, both
static and dynamic properties display fluid-like behavior up to a density
{\rho}c (L), which is the finite-size counterpart of the critical density
{\rho}c = {\rho}c (L \rightarrow \infty). We determine this density from the
cross-over behavior of the average size of the largest cluster. We then show
that several dynamical characteristics undergo a qualitative change at this
density. In particular, the size distribution of the largest cluster at the
moment of relocation, the persistence properties of the largest cluster and
correlations in its motion are studied.Comment: http://pre.aps.org/abstract/PRE/v82/i3/e03111
Experimental quantum verification in the presence of temporally correlated noise
Growth in the complexity and capabilities of quantum information hardware
mandates access to practical techniques for performance verification that
function under realistic laboratory conditions. Here we experimentally
characterise the impact of common temporally correlated noise processes on both
randomised benchmarking (RB) and gate-set tomography (GST). We study these
using an analytic toolkit based on a formalism mapping noise to errors for
arbitrary sequences of unitary operations. This analysis highlights the role of
sequence structure in enhancing or suppressing the sensitivity of quantum
verification protocols to either slowly or rapidly varying noise, which we
treat in the limiting cases of quasi-DC miscalibration and white noise power
spectra. We perform experiments with a single trapped Yb ion as a
qubit and inject engineered noise () to probe protocol
performance. Experiments on RB validate predictions that the distribution of
measured fidelities over sequences is described by a gamma distribution varying
between approximately Gaussian for rapidly varying noise, and a broad, highly
skewed distribution for the slowly varying case. Similarly we find a strong
gate set dependence of GST in the presence of correlated errors, leading to
significant deviations between estimated and calculated diamond distances in
the presence of correlated errors. Numerical simulations demonstrate
that expansion of the gate set to include negative rotations can suppress these
discrepancies and increase reported diamond distances by orders of magnitude
for the same error processes. Similar effects do not occur for correlated
or errors or rapidly varying noise processes,
highlighting the critical interplay of selected gate set and the gauge
optimisation process on the meaning of the reported diamond norm in correlated
noise environments.Comment: Expanded and updated analysis of GST, including detailed examination
of the role of gauge optimization in GST. Full GST data sets and
supplementary information available on request from the authors. Related
results available from
http://www.physics.usyd.edu.au/~mbiercuk/Publications.htm
Manifolds associated with -colored regular graphs
In this article we describe a canonical way to expand a certain kind of
-colored regular graphs into closed -manifolds by
adding cells determined by the edge-colorings inductively. We show that every
closed combinatorial -manifold can be obtained in this way. When ,
we give simple equivalent conditions for a colored graph to admit an expansion.
In addition, we show that if a -colored regular graph
admits an -skeletal expansion, then it is realizable as the moment graph of
an -dimensional closed -manifold.Comment: 20 pages with 9 figures, in AMS-LaTex, v4 added a new section on
reconstructing a space with a -action for which its moment graph is
a given colored grap
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