14,053 research outputs found
Constraints on a possible dineutron state from pionless EFT
We investigate the sensitivity of the three-nucleon system to changes in the
neutron-neutron scattering length to next-to-leading order in the pionless
effective field theory, focusing on the the triton-3He binding energy
difference and neutron-deuteron elastic scattering. Due to the appearance of an
electromagnetic three-body counterterm at this order, the triton-3He binding
energy difference remains consistent with the experimental value even for large
positive neutron-neutron scattering lengths while the elastic neutron-deuteron
scattering phase shifts are insensitive. We conclude that a bound dineutron
cannot be excluded to next-to-leading order in pionless EFT.Comment: 11 pages, 5 figure
On Mirror Symmetry for Calabi-Yau Fourfolds with Three-Form Cohomology
We study the action of mirror symmetry on two-dimensional N=(2,2) effective
theories obtained by compactifying Type IIA string theory on Calabi-Yau
fourfolds. Our focus is on fourfold geometries with non-trivial three-form
cohomology. The couplings of the massless zero-modes arising by expanding in
these forms depend both on the complex structure deformations and the Kahler
structure deformations of the Calabi-Yau fourfold. We argue that two
holomorphic functions of the deformation moduli capture this information. These
are exchanged under mirror symmetry, which allows us to derive them at the
large complex structure and large volume point. We discuss the application of
the resulting explicit expression to F-theory compactifications and their weak
string coupling limit. In the latter orientifold settings we demonstrate
compatibility with mirror symmetry of Calabi-Yau threefolds at large complex
structure. As a byproduct we find an interesting relation of no-scale like
conditions on Kahler potentials to the existence of chiral and twisted-chiral
descriptions in two dimensions.Comment: 36 page
Low-energy p-d scattering and He-3 in pionless EFT
We calculate low-energy proton--deuteron scattering in the framework of
pionless effective field theory. In the quartet channel, we calculate the
elastic scattering phase shift up to next-to-next-to-leading order in the power
counting. In the doublet channel, we perform a next-to-leading order
calculation. We obtain good agreement with the available phase shift analyses
down to the scattering threshold. The phase shifts in the region of
non-perturbative Coulomb interactions are calculated by using an optimised
integration mesh. Moreover, the Coulomb contribution to the 3He-3H binding
energy difference is evaluated in first order perturbation theory. We comment
on the implications of our results for the power counting of subleading
three-body forces.Comment: 27 pages, 13 figures, typos corrected in Sec. V.A (trinucleon wave
functions
Cracking the role of cocaine in stroke
No abstract available
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