123 research outputs found
Single-mode tunable erbium:ytterbium fibre Fabry-Perot laser
A compact tunable single-mode fiber laser is developed by using a novel combination of high-gain erbium: ytterbium (Er:Yb) phosphate fiber and fiber Fabry-Perot (FFP) cavity configurations. Experiments demonstrate the shortest Er:Yb phosphate FFP laser ever reported, which has a 100µm cavity length with a continuous wavelength tuning range over 4.52nm, as limited by the sharp fiber gain peak. In addition, an alternative 3-mirror laser design has also demonstrated single-mode lasing operation
A hidden Goldstone mechanism in the Kagom\'e lattice antiferromagnet
In this paper, we study the phases of the Heisenberg model on the \kagome
lattice with antiferromagnetic nearest neighbour coupling and
ferromagnetic next neighbour coupling . Analysing the long wavelength, low
energy effective action that describes this model, we arrive at the phase
diagram as a function of . The interesting part of
this phase diagram is that for small , which includes , there is
a phase with no long range spin order and with gapless and spin zero low lying
excitations. We discuss our results in the context of earlier, numerical and
experimental work.Comment: 21 pages, latex file with 5 figure
Domain-wall/Cosmology correspondence in adS/dS supergravity
We realize the domain-wall/cosmology correspondence for
(pseudo)supersymmetric domain walls (cosmologies) in the context of
four-dimensional supergravity. The OSp(2|4)-invariant anti-de Sitter (adS)
vacuum of a particular N=2 Maxwell-Einstein supergravity theory is shown to
correspond to the OSp(2^*|2,2)-invariant de Sitter (dS) vacuum of a particular
pseudo-supergravity model, with `twisted' reality conditions on spinors. More
generally, supersymmetric domain walls of the former model correspond to
pseudo-supersymmetric cosmologies of the latter model, with time-dependent
pseudo-Killing spinors that we give explicitly.Comment: 21 pages;v2: rewritten to clarify the link with fake supergravity --
main results unchanged; v3: typos corrected, two refs added, JHEP versio
A Step Beyond the Bounce: Bubble Dynamics in Quantum Phase Transitions
We study the dynamical evolution of a phase interface or bubble in the
context of a \lambda \phi^4 + g \phi^6 scalar quantum field theory. We use a
self-consistent mean-field approximation derived from a 2PI effective action to
construct an initial value problem for the expectation value of the quantum
field and two-point function. We solve the equations of motion numerically in
(1+1)-dimensions and compare the results to the purely classical evolution. We
find that the quantum fluctuations dress the classical profile, affecting both
the early time expansion of the bubble and the behavior upon collision with a
neighboring interface.Comment: 12 pages, multiple figure
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