34,646 research outputs found
Comment on "138La-138Ce-136Ce nuclear cosmochronometer of the supernova neutrino process"
The nuclear chosmochronometer suggested by Hayakawa et al. [Phys. Rev.C 77,
065802 (2008)] based on the 138La-138Ce-136Ce abundance ratio in presolar
grains would be affected by the existence of a hitherto unknown low-energy 1+
state in 138La. Results of a recent high-resolution study of the 138Ba(3He,t)
reaction under kinematics selectively populating 1+ states in 138La through
Gamow-Teller transitions provides strong evidence against the existence of such
a hypothetical state.Comment: Comment on Phys. Rev. C 77, 065802 (2008), submittted to Phys. Rev.
Generation of pulse trains by current-controlled magnetic mirrors
The evolution of a spin-wave packet trapped between two direct
current-carrying wires placed on the surface of a ferrite film is observed by
Brillouin light scattering. The wires act as semi-transparent mirrors confining
the packet. Because the spin-wave energy partially passes through these
mirrors, trains of spin-wave packets are generated outside the trap. A
numerical model of this process is presented and applied to the case when the
current in the wires is dynamically controlled. This dynamical control of the
mirror reflectivity provides new functionalities interesting for the field of
spin-wave logic like that of a spin-wave memory cell.Comment: 4 pages, 3 figure
Strong entanglement causes low gate fidelity in inaccurate one-way quantum computation
We study how entanglement among the register qubits affects the gate fidelity
in the one-way quantum computation if a measurement is inaccurate. We derive an
inequality which shows that the mean gate fidelity is upper bounded by a
decreasing function of the magnitude of the error of the measurement and the
amount of the entanglement between the measured qubit and other register
qubits. The consequence of this inequality is that, for a given amount of
entanglement, which is theoretically calculated once the algorithm is fixed, we
can estimate from this inequality how small the magnitude of the error should
be in order not to make the gate fidelity below a threshold, which is specified
by a technical requirement in a particular experimental setup or by the
threshold theorem of the fault-tolerant quantum computation.Comment: 4 pages, 3 figure
Electric dipole response of 208Pb from proton inelastic scattering: constraints on neutron skin thickness and symmetry energy
The electric dipole (E1) response of 208Pb has been precisely determined by
measuring Coulomb excitation induced by proton scattering at very forward
angles. The electric dipole polarizability, defined as inverse energy-weighted
sum rule of the E1 strength, has been extracted as 20.1+-0.6 fm^3. The data can
be used to constrain the neutron skin thickness of 208Pb to
0.168(+-0.009)_expt(+-0.013)_theo(+-0.021)_est fm, where the subscript "expt"
refers to the experimental uncertainty, "theor" to the theoretical confidence
band and "est" to the uncertainty associated with the estimation of the
symmetry energy at the saturation density. In addition, a constraint band has
been extracted in the plane of the symmetry energy (J) and its slope parameter
(L) at the saturation density.Comment: 6 pages, 8 figures, revised manuscript submitted to special volume of
Eur. Phys. J. A on symmetry energ
The Right Mutation Strength for Multi-Valued Decision Variables
The most common representation in evolutionary computation are bit strings.
This is ideal to model binary decision variables, but less useful for variables
taking more values. With very little theoretical work existing on how to use
evolutionary algorithms for such optimization problems, we study the run time
of simple evolutionary algorithms on some OneMax-like functions defined over
. More precisely, we regard a variety of
problem classes requesting the component-wise minimization of the distance to
an unknown target vector . For such problems we see a crucial
difference in how we extend the standard-bit mutation operator to these
multi-valued domains. While it is natural to select each position of the
solution vector to be changed independently with probability , there are
various ways to then change such a position. If we change each selected
position to a random value different from the original one, we obtain an
expected run time of . If we change each selected position
by either or (random choice), the optimization time reduces to
. If we use a random mutation strength with probability inversely proportional to and change
the selected position by either or (random choice), then the
optimization time becomes , bringing down
the dependence on from linear to polylogarithmic. One of our results
depends on a new variant of the lower bounding multiplicative drift theorem.Comment: an extended abstract of this work is to appear at GECCO 201
Theoretical Setting of Inner Reversible Quantum Measurements
We show that any unitary transformation performed on the quantum state of a
closed quantum system, describes an inner, reversible, generalized quantum
measurement. We also show that under some specific conditions it is possible to
perform a unitary transformation on the state of the closed quantum system by
means of a collection of generalized measurement operators. In particular,
given a complete set of orthogonal projectors, it is possible to implement a
reversible quantum measurement that preserves the probabilities. In this
context, we introduce the concept of "Truth-Observable", which is the physical
counterpart of an inner logical truth.Comment: 11 pages. More concise, shortened version for submission to journal.
References adde
Properties of the first excited state of 9Be derived from (gamma,n) and (e,e') reactions
Properties of the first excited state of the nucleus 9Be are discussed based
on recent (e,e') and (gamma,n) experiments. The parameters of an R-matrix
analysis of different data sets are consistent with a resonance rather than a
virtual state predicted by some model calculations. The energy and the width of
the resonance are deduced. Their values are rather similar for all data sets,
and the energy proves to be negative. It is argued that the disagreement
between the extracted B(E1) values may stem from different ways of integration
of the resonance. If corrected, fair agreement between the (e,e') and one of
the (gamma,n) data sets is found. A recent (gamma,n) experiment at the HIgS
facility exhibits larger cross sections close to the neutron threshold which
remain to be explained.Comment: 5 pages, accepted fro publication in Phys. Rev.
Bistable Chimera Attractors on a Triangular Network of Oscillator Populations
We study a triangular network of three populations of coupled phase
oscillators with identical frequencies. The populations interact nonlocally, in
the sense that all oscillators are coupled to one another, but more weakly to
those in neighboring populations than to those in their own population. This
triangular network is the simplest discretization of a continuous ring of
oscillators. Yet it displays an unexpectedly different behavior: in contrast to
the lone stable chimera observed in continuous rings of oscillators, we find
that this system exhibits \emph{two coexisting stable chimeras}. Both chimeras
are, as usual, born through a saddle node bifurcation. As the coupling becomes
increasingly local in nature they lose stability through a Hopf bifurcation,
giving rise to breathing chimeras, which in turn get destroyed through a
homoclinic bifurcation. Remarkably, one of the chimeras reemerges by a reversal
of this scenario as we further increase the locality of the coupling, until it
is annihilated through another saddle node bifurcation.Comment: 12 pages, 5 figure
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