339 research outputs found
Broken parity and a chiral ground state in the frustrated magnet CdCr2O4
We present a model describing the lattice distortion and incommensurate
magnetic order in the spinel CdCr2O4, a good realization of the Heisenberg
"pyrochlore" antiferromagnet. The magnetic frustration is relieved through the
spin-Peierls distortion of the lattice involving a phonon doublet with odd
parity. The distortion stablizes a collinear magnetic order with the
propagation wavevector q=2\pi(0,0,1). The lack of inversion symmetry makes the
crystal structure chiral. The handedness is transferred to magnetic order by
the relativistic spin-orbit coupling: the collinear state is twisted into a
long spiral with the spins in the ac plane and q shifted to 2\pi(0,\delta,1).Comment: Incremental changes in response to referee report
Impact of Immigrant Entrepreneurs and Workers in Leisure and Hospitality Businesses: Massachusetts and New England
This report examines the role and impact of immigrant entrepreneurs and workers on Leisure and Hospitality businesses in New England, particularly Massachusetts. A significant portion of state economies in New England, especially in Massachusetts, relies heavily on the employment of the foreign-born. As the native workforce ages and population growth declines, businesses are becoming increasingly dependent upon the availability of the foreign-born. This development has facilitated an increasingly significant presence and role of immigrant entrepreneurs in Leisure and Hospitality businesses that is documented for the first time in this report
Physics of Trans-Planckian Gravity
We study the field theoretical description of a generic theory of gravity
flowing to Einstein General Relativity in IR. We prove that, if ghost-free, in
the weakly coupled regime such a theory can never become weaker than General
Relativity. Using this fact, as a byproduct, we suggest that in a ghost-free
theory of gravity trans-Planckian propagating quantum degrees of freedom cannot
exist. The only physical meaning of a trans-Planckian pole is the one of a
classical state (Black Hole) which is described by the light IR quantum degrees
of freedom and gives exponentially-suppressed contributions to virtual
processes. In this picture Einstein gravity is UV self-complete, although not
Wilsonian, and sub-Planckian distances are unobservable in any healthy theory
of gravity. We then finally show that this UV/IR correspondence puts a severe
constraint on any attempt of conventional Wilsonian UV-completion of
trans-Planckian gravity. Specifically, there is no well-defined energy domain
in which gravity could become asymptotically weak or safe.Comment: 23 pages, 4 figures, v2: Paper reorganized to improve clarity;
additional explanations and references added; version accepted for
publication in Phys. Rev.
Fractional vortices and composite domain walls in flat nanomagnets
We provide a simple explanation of complex magnetic patterns observed in
ferromagnetic nanostructures. To this end we identify elementary topological
defects in the field of magnetization: ordinary vortices in the bulk and
vortices with half-integer winding numbers confined to the edge. Domain walls
found in experiments and numerical simulations in strips and rings are
composite objects containing two or more of the elementary defects.Comment: Minor changes: updated references and fixed typo
Predictive Power of Strong Coupling in Theories with Large Distance Modified Gravity
We consider theories that modify gravity at cosmological distances, and show
that any such theory must exhibit a strong coupling phenomenon, or else it is
either inconsistent or is already ruled out by the solar system observations.
We show that all the ghost-free theories that modify dynamics of spin-2
graviton on asymptotically flat backgrounds, automatically have this property.
Due to the strong coupling effect, modification of the gravitational force is
source-dependent, and for lighter sources sets in at shorter distances. This
universal feature makes modified gravity theories predictive and potentially
testable not only by cosmological observations, but also by precision
gravitational measurements at scales much shorter than the current cosmological
horizon. We give a simple parametrization of consistent large distance modified
gravity theories and their predicted deviations from the Einsteinian metric
near the gravitating sources.Comment: 12 pages, Latex, to be published in New Journal of Physic
Spin superstructure and noncoplanar ordering in metallic pyrochlore magnets with degenerate orbitals
We study double-exchange models with itinerant t2g electrons in spinel and
pyrochlore crystals. In both cases the localized spins form a network of
corner-sharing tetrahedra. We show that the strong directional dependence of
t2g orbitals leads to unusual Fermi surfaces that induce spin superstructures
and noncoplanar orderings for a weak coupling between itinerant electrons and
localized spins. Implications of our results to ZnV2O4 and Cd2Os2O7 are also
discussed.Comment: 4 pages, 3 figure
Community Leadership Institute of Kentucky
The Community Leadership Institute of Kentucky(CLIK) aims to improve community research capacity to address health disparities in communities, particularly Appalachia.
Established in 2014, through a partnership of the UK Center of Excellence in Rural Health, the UK Center for Clinical and Translational Science Community Engagement Program, and the Kentucky Office of Rural Health, the intensive four-week training provides: Training in research and leadership Funding for community research projects Technical support for up to one year as participants implement community research projects
Up to 12 slots are available annually, with priority given to leaders from Appalachian Kentucky and to projects related to key areas of research interest, including: Cancer prevention (e.g., nutrition, physical activity, smoking cessation) Reducing obesity and sedentary lifestyle Prevention and management of chronic diseases (e.g., diabetes and cardiovascular disease) Prevention and treatment of substance abus
Classical Dimensional Transmutation and Confinement
We observe that probing certain classical field theories by external sources
uncovers the underlying renormalization group structure, including the
phenomenon of dimensional transmutation, at purely-classical level. We perform
this study on an example of theory and unravel asymptotic
freedom and triviality for negative and positives signs of
respectively. We derive exact classical function equation. Solving this
equation we find that an isolated source has an infinite energy and therefore
cannot exist as an asymptotic state. On the other hand a dipole, built out of
two opposite charges, has finite positive energy. At large separation the
interaction potential between these two charges grows indefinitely as a
distance in power one third
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