12,365 research outputs found
Signatures of S-wave bound-state formation in finite volume
We discuss formation of an S-wave bound-state in finite volume on the basis
of L\"uscher's phase-shift formula.It is found that although a bound-state pole
condition is fulfilled only in the infinite volume limit, its modification by
the finite size corrections is exponentially suppressed by the spatial extent
in a finite box . We also confirm that the appearance of the S-wave
bound state is accompanied by an abrupt sign change of the S-wave scattering
length even in finite volume through numerical simulations. This distinctive
behavior may help us to discriminate the loosely bound state from the lowest
energy level of the scattering state in finite volume simulations.Comment: 25 pages, 30 figures; v2: typos corrected and two references added,
v3: final version to appear in PR
Deconstructing triplet nucleon-nucleon scattering
Nucleon-nucleon scattering in spin-triplet channels is analysed within an
effective field theory where one-pion exchange is treated nonperturbatively.
Justifying this requires the identification of an additional low-energy scale
in the strength of that potential. Short-range interactions are organised
according to the resulting power counting, in which the leading term is
promoted to significantly lower order than in the usual perturbative counting.
In each channel there is a critical momentum above which the waves probe the
singular core of the tensor potential and the new counting is necessary. When
the effects of one- and two-pion exchange have been removed using a
distorted-wave Born approximation, the residual scattering in waves with L<=2
is well described by the first three terms in the new counting. In contrast,
the scattering in waves with L>=3 is consistent with the perturbative counting,
at least for energies up to 300 MeV. This pattern is in agreement with
estimates of the critical momenta in these channels.Comment: 13 pages, RevTeX, 8 figures, minor clarifications adde
Levinson's Theorem for Non-local Interactions in Two Dimensions
In the light of the Sturm-Liouville theorem, the Levinson theorem for the
Schr\"{o}dinger equation with both local and non-local cylindrically symmetric
potentials is studied. It is proved that the two-dimensional Levinson theorem
holds for the case with both local and non-local cylindrically symmetric cutoff
potentials, which is not necessarily separable. In addition, the problems
related to the positive-energy bound states and the physically redundant state
are also discussed in this paper.Comment: Latex 11 pages, no figure, submitted to J. Phys. A Email:
[email protected], [email protected]
Scattering by a contact potential in three and lower dimensions
We consider the scattering of nonrelativistic particles in three dimensions
by a contact potential which is defined
as the limit of . It is
surprising that it gives a nonvanishing cross section when and
. When the contact potential is approached by a spherical square
well potential instead of the above spherical shell one, one obtains basically
the same result except that the parameter that gives a nonvanishing
cross section is different. Similar problems in two and one dimensions are
studied and results of the same nature are obtained.Comment: REVTeX, 9 pages, no figur
The equation of state of neutron star matter and the symmetry energy
We present an overview of microscopical calculations of the Equation of State
(EOS) of neutron matter performed using Quantum Monte Carlo techniques. We
focus to the role of the model of the three-neutron force in the high-density
part of the EOS up to a few times the saturation density. We also discuss the
interplay between the symmetry energy and the neutron star mass-radius
relation.
The combination of theoretical models of the EOS with recent neutron stars
observations permits us to constrain the value of the symmetry energy and its
slope. We show that astrophysical observations are starting to provide
important insights into the properties of neutron star matter.Comment: 7 pages, 3 figure, talk given at the 11th International Conference on
Nucleus-Nucleus Collisions (NN2012), San Antonio, Texas, USA, May 27-June 1,
2012. To appear in the NN2012 Proceedings in Journal of Physics: Conference
Series (JPCS
Nilsson diagrams for light neutron-rich nuclei with weakly-bound neutrons
Using Woods-Saxon potentials and the eigenphase formalism for one-particle
resonances, one-particle bound and resonant levels for neutrons as a function
of quadrupole deformation are presented, which are supposed to be useful for
the interpretation of spectroscopic properties of some light neutron-rich
nuclei with weakly-bound neutrons. Compared with Nilsson diagrams in text books
which are constructed using modified oscillator potentials, we point out a
systematic change of the shell structure in connection with both weakly-bound
and resonant one-particle levels related to small orbital angular momenta
. Then, it is seen that weakly-bound neutrons in nuclei such as
C and Mg may prefer to being deformed as a result of
Jahn-Teller effect, due to the near degeneracy of the 1d-2s
levels and the 1f-2p levels in the spherical potential,
respectively. Furthermore, the absence of some one-particle resonant levels
compared with the Nilsson diagrams in text books is illustrated.Comment: 12 pages, 5 figure
ELECTRON IMPACT EXCITATION EFFICIENCY CURVES FOR THE FORMATION OF NEUTRAL METASTABLE SPECIES.
Formation spectra of light kaonic nuclei by in-flight () reactions with chiral unitary amplitude
We study theoretically the in-flight () reactions for the formation of
light kaonic nuclear systems to get deeper physical insights on the expected
spectra, and to investigate the experimental feasibility of the reaction at new
facilities like J-PARC. We show the expected spectra for the formation of the
, and -B systems which are accessible by the
() experiments. By considering the conversion part of the Green's
function, we can show the missing mass spectra of the () reactions
coincidence with the particle emissions due to absorption in processes. To calculate the cross sections, we use the so-called
approximation to evaluate the optical potential. As for the amplitude
, we adopt the chiral unitary amplitude of channel in vacuum for
simplicity, and we also check the medium effects by applying the chiral
amplitude at finite density. The effects of the p-wave optical potential of
(1385) channel and the contribution from mixing in
He() reaction are also evaluated numerically. To understand the
meanings of the spectrum shape, we also study the behavior of the poles of kaon
Green's function in nuclear matter. We conclude that He() and
He() reactions coincident with the emission due to
absorption may show the certain structure in the bound region
spectra indicating the existence of the unstable kaonic nuclear bound states.
As for the C() spectra with the emission, we may also
observe the structure in the bound region, however, we need to evaluate the
medium effects carefully for larger nuclei.Comment: 14 pages, 12 figure
Explosive events associated with a surge
The solar atmosphere contains a wide variety of small-scale transient
features. Here, we explore the inter-relation between some of them such as
surges, explosive events and blinkers via simultaneous spectral and imaging
data taken with the TRACE imager, the SUMER, and CDS spectrometers on board
SoHO, and SVST La Palma. The alignment of all data both in time and solar XY
shows that SUMER line profiles, which are attributed to explosive events, are
due to a surge phenomenon. The surge is triggered, most probably, by one or
more Elerman bombs which are best visible in Halpha +-350 A but were also
registered by TRACE Fe IX/X 171 A and correspond to a strong radiance increase
in the CDS Mg IX 368.07 A line. With the present study we demonstrate that the
division of small-scale transient events into a number of different subgroups,
for instance explosive events, blinkers, spicules, surges or just brightenings,
is ambiguous, implying that the definition of a feature based only on either
spectroscopic or imaging characteristics as well as insufficient spectral and
spatial resolution can be incomplete.Comment: 17 pages, 7 figures, 1 tabl
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