16,175 research outputs found
Deducing spectroscopic factors from wave-function asymptotics
In a coupled-channel model, we explore the effects of coupling between
configurations on the radial behavior of the wave function and, in particular,
on the spectroscopic factor (SF) and the asymptotic normalization coefficient
(ANC). We evaluate the extraction of a SF from the ratio of the ANC of the
coupled-channel model to that of a single-particle approximation of the wave
function. We perform this study within a core + n collective model, which
includes two states of the core that connect by a rotational coupling. To get
additional insights, we also use a simplified model that takes a delta function
for the coupling potential. Calculations are performed for 11Be. Fair agreement
is obtained between the SF inferred from the single-particle approximation and
the one obtained within the coupled-channel models. Significant discrepancies
are observed only for large coupling strength and/or large admixture, that is,
a small SF. This suggests that reliable SFs can be deduced from the
wave-function asymptotics when the structure is dominated by one configuration,
that is, for a large SF.Comment: Title correcte
On complexified analytic Hamiltonian flows and geodesics on the space of Kahler metrics
In the case of a compact real analytic symplectic manifold M we describe an
approach to the complexification of Hamiltonian flows [Se, Do1, Th1] and
corresponding geodesics on the space of Kahler metrics. In this approach,
motivated by recent work on quantization, the complexified Hamiltonian flows
act, through the Grobner theory of Lie series, on the sheaf of complex valued
real analytic functions, changing the sheaves of holomorphic functions. This
defines an action on the space of (equivalent) complex structures on M and also
a direct action on M. This description is related to the approach of [BLU]
where one has an action on a complexification M_C of M followed by projection
to M. Our approach allows for the study of some Hamiltonian functions which are
not real analytic. It also leads naturally to the consideration of continuous
degenerations of diffeomorphisms and of Kahler structures of M. Hence, one can
link continuously (geometric quantization) real, and more general non-Kahler,
polarizations with Kahler polarizations. This corresponds to the extension of
the geodesics to the boundary of the space of Kahler metrics. Three
illustrative examples are considered. We find an explicit formula for the
complex time evolution of the Kahler potential under the flow. For integral
symplectic forms, this formula corresponds to the complexification of the
prequantization of Hamiltonian symplectomorphisms. We verify that certain
families of Kahler structures, which have been studied in geometric
quantization, are geodesic families.Comment: final versio
Scalar field phase dynamics in preheating
We study the model of a massive inflaton field coupled to another
scalar filed with interaction term for the first stage
of preheating. We obtain the the behavior of the phase in terms of the
iteration of a simple family of circle maps. When expansion of the universe is
taken into account the qualitative behavior of the phase and growth number
evolution is reminiscent of the behavior found in the case without expansion.Comment: 4 pages, 4 figures, LaTeX; submitted to the Proceedings of Eleventh
Marcel Grossmann Meetin
Comparing non-perturbative models of the breakup of neutron-halo nuclei
Breakup reactions of loosely-bound nuclei are often used to extract structure
and/or astrophysical information. Here we compare three non-perturbative
reaction theories often used when analyzing breakup experiments, namely the
continuum discretized coupled channel model, the time-dependent approach
relying on a semiclassical approximation, and the dynamical eikonal
approximation. Our test case consists of the breakup of 15C on Pb at 68
MeV/nucleon and 20 MeV/nucleon.Comment: 8 pages, 6 figures, accepted for publication in Phys. Rev.
Large N WZW Field Theory Of N=2 Strings
We explore the quantum properties of self-dual gravity formulated as a large
two-dimensional WZW sigma model. Using a non-trivial classical background,
we show that a space-time is generated. The theory contains an infinite
series of higher point vertices. At tree level we show that, in spite of the
presence of higher than cubic vertices, the on-shell 4 and higher point
functions vanish, indicating that this model is related with the field theory
of closed N=2 strings. We examine the one-loop on-shell 3-point amplitude and
show that it is ultra-violet finite.Comment: This is the final version. By editorial mistake at Phys.Lett.B an
older version was published in prin
Asymptotic normalization of mirror states and the effect of couplings
Assuming that the ratio between asymptotic normalization coefficients of
mirror states is model independent, charge symmetry can be used to indirectly
extract astrophysically relevant proton capture reactions on proton-rich nuclei
based on information on stable isotopes. The assumption has been tested for
light nuclei within the microscopic cluster model. In this work we explore the
Hamiltonian independence of the ratio between asymptotic normalization
coefficients of mirror states when deformation and core excitation is
introduced in the system. For this purpose we consider a phenomenological rotor
+ N model where the valence nucleon is subject to a deformed mean field and the
core is allowed to excite. We apply the model to 8Li/8B, 13C/13N, 17O/17F,
23Ne/23Al, and 27Mg/27P. Our results show that for most studied cases, the
ratio between asymptotic normalization coefficients of mirror states is
independent of the strength and multipolarity of the couplings induced. The
exception is for cases in which there is an s-wave coupled to the ground state
of the core, the proton system is loosely bound, and the states have large
admixture with other configurations. We discuss the implications of our results
for novae.Comment: 8 pages, 2 figures, submitted to PR
Geometric quantization, complex structures and the coherent state transform
It is shown that the heat operator in the Hall coherent state transform for a
compact Lie group is related with a Hermitian connection associated to a
natural one-parameter family of complex structures on . The unitary
parallel transport of this connection establishes the equivalence of
(geometric) quantizations of for different choices of complex structures
within the given family. In particular, these results establish a link between
coherent state transforms for Lie groups and results of Hitchin and Axelrod,
Della Pietra and Witten.Comment: to appear in Journal of Functional Analysi
- …