780 research outputs found
Casimir Force between two Half Spaces of Vortex Matter in Anisotropic Superconductors
We present a new approach to calculate the attractive long-range
vortex-vortex interaction of the van der Waals type present in anisotropic and
layered superconductors. The mapping of the statistical mechanics of
two-dimensional charged bosons allows us to define a Casimir problem: Two half
spaces of vortex matter separated by a gap of width R are mapped to two
dielectric half planes of charged bosons interacting via a massive gauge field.
We determine the attractive Casimir force between the two half planes and show
that it agrees with the pairwise summation of the van der Waals force between
vortices.Comment: Submitted to Physica C (4 pages, 2 figures
Strongly correlated 2D quantum phases with cold polar molecules: controlling the shape of the interaction potential
We discuss techniques to tune and shape the long-range part of the
interaction potentials in quantum gases of polar molecules by dressing
rotational excitations with static and microwave fields. This provides a novel
tool towards engineering strongly correlated quantum phases in combination with
low dimensional trapping geometries. As an illustration, we discuss a 2D
crystalline phase, and a superfluid-crystal quantum phase transition.Comment: 4 pages, 3 figure
Commensurate-incommensurate transition of cold atoms in an optical lattice
An atomic gas subject to a commensurate periodic potential generated by an
optical lattice undergoes a superfluid--Mott insulator transition. Confining a
strongly interacting gas to one dimension generates an instability where an
arbitrary weak potential is sufficient to pin the atoms into the Mott state;
here, we derive the corresponding phase diagram. The commensurate pinned state
may be detected via its finite excitation gap and the Bragg peaks in the static
structure factor.Comment: 4 pages, 2 figure
The nucleon axial-vector coupling beyond one loop
We analyze the nucleon axial-vector coupling to two loops in chiral
perturbation theory. We show that chiral extrapolations based on this
representation require lattice data with pion masses below 300 MeV.Comment: 9 pp, 2 fig
The role of octreotide in preventing complications after pancreatoduodenectomy for cancer
Background Although the mortality rate of pancreatoduodenectomy has fallen sharply over the last two decades, there is still a risk of serious complications resulting from leakage at the site of anastomosis between the pancreatic remnant and the gastrointestinal tract. Numerous techniques have been described to minimise the risk of these anastomotic leaks, but they can be difficult to avoid if the distal pancreas is unobstructed with a soft parenchyma and a non-dilated duct. The risk of leakage is largely dependent upon the presence of activated pancreatic enzymes, and this fact provides a rationale for the perioperative use of the somatostatin analogue octreotide to inhibit exocrine pancreatic secretion. Discussion Six prospective randomised controlled trials have been published on the use of prophylactic octreotide in pancreatic surgery, five from Europe and one from the USA. The five (multicentre) European studies have consistently shown that octreotide reduces the postoperative complication rate, but the American study does not confirm this benefit. Methodological differences may explain the discrepancy, notably the fact that most of the US patients had received preoperative chemoradiation which is likely to have reduced enzyme secretion. A meta-analysis of four of these studies showed that octreotide lowered the rate of postoperative complications from 37 to 21%, chiefly by reducing the risk of pancreatic fistula. Prophylactic octreotide therapy is cost effective and should be used at least in patients with normal pancreatic parenchyma
Renormalization group equations for effective field theories
We derive the renormalization group equations for a generic nonrenormalizable
theory. We show that the equations allow one to derive the structure of the
leading divergences at any loop order in terms of one-loop diagrams only. In
chiral perturbation theory, e.g., this means that one can obtain the series of
leading chiral logs by calculating only one loop diagrams. We discuss also the
renormalization group equations for the subleading divergences, and the crucial
role of counterterms that vanish at the equations of motion. Finally, we show
that the renormalization group equations obtained here apply equally well also
to renormalizable theories.Comment: 40 pages, 4 figures, plain Late
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