4,610 research outputs found
Weak Gravity Conjecture for the Effective Field Theories with N Species
We conjecture an intrinsic UV cutoff for the validity of the effective field
theory with a large number of species coupled to gravity. In four dimensions
such a UV cutoff takes the form for scalar
fields with the same potential , . This conjecture
implies that the assisted chaotic inflation or N-flation might be in the
swampland, not in the landscape. Similarly a UV cutoff
is conjectured for the U(1) gauge theory with species.Comment: 12 pages; refs added and some statements clarifie
Formation of superheavy nuclei in cold fusion reactions
Within the concept of the dinuclear system (DNS), a dynamical model is
proposed for describing the formation of superheavy nuclei in complete fusion
reactions by incorporating the coupling of the relative motion to the nucleon
transfer process. The capture of two heavy colliding nuclei, the formation of
the compound nucleus and the de-excitation process are calculated by using an
empirical coupled channel model, solving a master equation numerically and
applying statistical theory, respectively. Evaporation residue excitation
functions in cold fusion reactions are investigated systematically and compared
with available experimental data. Maximal production cross sections of
superheavy nuclei in cold fusion reactions with stable neutron-rich projectiles
are obtained. Isotopic trends in the production of the superheavy elements
Z=110, 112, 114, 116, 118 and 120 are analyzed systematically. Optimal
combinations and the corresponding excitation energies are proposed.Comment: 18 pages, 8 figure
Bounds for eigenvalue ratios of the Laplacian
For a bounded domain with a piecewise smooth boundary in an
-dimensional Euclidean space , we study eigenvalues of the
Dirichlet eigenvalue problem of the Laplacian. First we give a general
inequality for eigenvalues of the Laplacian. As an application, we study lower
order eigenvalues of the Laplacian and derive the ratios of lower order
eigenvalues of the Laplacian.Comment: 14 page
Computation of the order low-energy constants with tensor sources
We present the results of calculations of the and order
low-energy constants for the chiral Lagrangian with tensor sources for both two
and three flavors of pseudoscalar mesons. This is a generalization of our
previous work on similar calculations without tensor sources in terms of the
quark self-energy , based on the first principle derivation of the
low-energy effective Lagrangian and computation of the low-energy constants
with some rough approximations. With the help of partial integration and some
epsilon relations, we find that some order operators with tensor sources
appearing in the literature are related to each other. That leaves 98
independent terms for -flavor, 92 terms for three-flavor, and 65 terms for
two-flavor cases. We also find that the odd-intrinsic-parity chiral Lagrangian
with tensor sources cannot independently exist in any order of low-energy
expansion.Comment: 29 page
Next-to-Leading Order Corrections to Single Top Quark Production and Decay at the Tevatron: 1. s-channel Process
We present a study of s-channel single top quark production at the upgraded
Tevatron collider, including the next-to-leading order (NLO) QCD
corrections to the production and the decay of the top quark. The "modified"
narrow width approximation was adopted to preserve the spin of the top quark in
its production and decay. We discuss the effect of the different
contributions on the inclusive cross section as well as various kinematic
distributions after imposing the relevant cuts to select s-channel single top
signal events. In particular the decay contribution, while small
in size, has a significant impact on several distributions. With the help of
the best-jet algorithm to reconstruct the top quark we demonstrate that it is
possible to study kinematical and spin correlations in s-channel single top
events. We furthermore compare top quark spin measurements in two different
basis and show how NLO corrections have to be taken into consideration in
searches for the Higgs boson through associated production at the
Tevatron.Comment: 39 pages, 37 figure
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