34,133 research outputs found
Homogeneous spin Riemannian manifolds with the simplest Dirac operator
We show the existence of nonsymmetric homogeneous spin Riemannian manifolds
whose Dirac operator is like that on a Riemannian symmetric spin space. Such
manifolds are exactly the homogeneous spin Riemannian manifolds which
are traceless cyclic with respect to some quotient expression and
reductive decomposition .
Using transversally symmetric fibrations of noncompact type, we give a list of
them
On a class of n-Leibniz deformations of the simple Filippov algebras
We study the problem of the infinitesimal deformations of all real, simple,
finite-dimensional Filippov (or n-Lie) algebras, considered as a class of
n-Leibniz algebras characterized by having an n-bracket skewsymmetric in its
n-1 first arguments. We prove that all n>3 simple finite-dimensional Filippov
algebras are rigid as n-Leibniz algebras of this class. This rigidity also
holds for the Leibniz deformations of the semisimple n=2 Filippov (i.e., Lie)
algebras. The n=3 simple FAs, however, admit a non-trivial one-parameter
infinitesimal 3-Leibniz algebra deformation. We also show that the
simple Filippov algebras do not admit non-trivial central extensions as
n-Leibniz algebras of the above class.Comment: 19 pages, 30 refs., no figures. Some text rearrangements for better
clarity, misprints corrected. To appear in J. Math. Phy
Nucleosynthesis in Type I X-ray Bursts
Type I X-ray bursts are thermonuclear explosions that occur in the envelopes
of accreting neutron stars. Detailed observations of these phenomena have
prompted numerous studies in theoretical astrophysics and experimental nuclear
physics since their discovery over 35 years ago. In this review, we begin by
discussing key observational features of these phenomena that may be sensitive
to the particular patterns of nucleosynthesis from the associated thermonuclear
burning. We then summarize efforts to model type I X-ray bursts, with emphasis
on determining the nuclear physics processes involved throughout these bursts.
We discuss and evaluate limitations in the models, particularly with regard to
key uncertainties in the nuclear physics input. Finally, we examine recent,
relevant experimental measurements and outline future prospects to improve our
understanding of these unique environments from observational, theoretical and
experimental perspectives.Comment: Accepted by Prog. Part. Nucl. Phys., 45 pages, 14 figure
Dynamical seesaw mechanism for Dirac neutrinos
So far we have not been able to establish that, as theoretically expected,
neutrinos are their own anti-particles. Here we propose a dynamical way to
account for the Dirac nature of neutrinos and the smallness of their mass in
terms of a new variant of the seesaw paradigm in which the energy scale of
neutrino mass generation could be accessible to the current LHC experiments.Comment: 7 pages, 1 figur
Functional analysis of novel genes differentially expressed genes in heart/hemangioblast precursor cells (H/HPC)
info:eu-repo/semantics/publishedVersio
Earnings Management to Avoid Losses: a cost of debt explanation
In this paper we analyze firms’ earnings management behavior to avoid losses conditional on the (asymmetric) incentive underlying market (positive/negative) returns. Our intuition is that firms with negative returns in the period (bad news, BN) face a higher incentive to undertake earnings management, and that their ultimate intention is to hide from credit markets a signal (loss) that could be translated into a negative impact on their cost of debt. The empirical evidence supports this intuition. BN firms show higher earnings management pervasiveness than their counterparts with good news (GN), and the set with simultaneous BN and prior period positive earnings undertake more pervasive earnings manipulation than BN firms in general. Within this restricted set of firms, and consistent with a cost of debt explanation, we find that firms with larger needs of debt show a higher incidence of earnings management to avoid losses. The overall empirical evidence challenges the implicit assumption in Burgstahler and Dichev (1997) that the incentive to manage earnings is homogeneous to all firms, and suggests that the discontinuities around zero in the earnings distributions are driven, at least partly, by firms’ earnings management behavior.earnings management, earnings thresholds, earnings discontinuities, cost of debt
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