18,401 research outputs found
Topologically Massive Gauge Theories and their Dual Factorised Gauge Invariant Formulation
There exists a well-known duality between the Maxwell-Chern-Simons theory and
the self-dual massive model in 2+1 dimensions. This dual description has been
extended to topologically massive gauge theories (TMGT) in any dimension. This
Letter introduces an unconventional approach to the construction of this type
of duality through a reparametrisation of the master theory action. The dual
action thereby obtained preserves the same gauge symmetry structure as the
original theory. Furthermore, the dual action is factorised into a propagating
sector of massive gauge invariant variables and a sector with gauge variant
variables defining a pure topological field theory. Combining results obtained
within the Lagrangian and Hamiltonian formulations, a new completed structure
for a gauge invariant dual factorisation of TMGT is thus achieved.Comment: 1+7 pages, no figure
The theory of coherent dynamic nuclear polarization in quantum dots
We consider the dynamic nuclear spin polarization (DNP) using two electrons
in a double quantum dot in presence of external magnetic field and spin-orbit
interaction, in various schemes of periodically repeated sweeps through the
S-T+ avoided crossing. By treating the problem semi-classically, we find that
generally the DNP have two distinct contributions - a geometrical polarization
and a dynamic polarization, which have different dependence on the control
parameters such as the sweep rates and waiting times in each period. Both terms
show non-trivial dependence on those control parameter. We find that even for
small spin-orbit term, the dynamical polarization dominates the DNP in presence
of a long waiting period near the S-T+ avoided crossing, of the order of the
nuclear Larmor precession periods. A detailed numerical analysis of a specific
control regime can explain the oscillations observed by Foletti et.~al.~in
arXiv:0801.3613.Comment: 22 pages, 6 figure
Modelling the Spatial Structure of Pig Production in Denmark
In Denmark, the concentration of pig production is highest in the western part of the country. However, there may be even larger local differences in the number of pigs produced. In this study we analyze the determinants of the location of pig production in Denmark with particular focus on spatial externalities and the interaction between the location of pig production and upstream sector and slaughterhouses. It is the assumption that the location of slaughterhouses is influenced by the location of the primary producers, implying that this variable is endogenous, whereas the location of primary producers is independent of the location of slaughterhouses. This is due to the fact that transportation costs of pigs are paid by the cooperatives owning the slaughterhouses. This assumption is tested applying a spatial econometric model. The model is estimated for 1999 and 2004. Furthermore, the impact of negative environmental externalities of pig production on location is analyzed. The results show that spatial externalities have a positive effect on the location of pig production whereas environmental regulation has a negative effect on location.Agglomeration, Externalities, Spatial Econometrics, Polluted Production, Livestock Production/Industries,
Zero modes, energy gap, and edge states of anisotropic honeycomb lattice in a magnetic field
We present systematic study of zero modes and gaps by introducing effects of
anisotropy of hopping integrals for a tight-binding model on the honeycomb
lattice in a magnetic field. The condition for the existence of zero modes is
analytically derived. From the condition, it is found that a tiny anisotropy
for graphene is sufficient to open a gap around zero energy in a magnetic
field. This gap behaves as a non-perturbative and exponential form as a
function of the magnetic field. The non-analytic behavior with respect to the
magnetic field can be understood as tunneling effects between energy levels
around two Dirac zero modes appearing in the honeycomb lattice, and an explicit
form of the gap around zero energy is obtained by the WKB method near the
merging point of these Dirac zero modes. Effects of the anisotropy for the
honeycomb lattices with boundaries are also studied. The condition for the
existence of zero energy edge states in a magnetic field is analytically
derived. On the basis of the condition, it is recognized that anisotropy of the
hopping integrals induces abrupt changes of the number of zero energy edge
states, which depend on the shapes of the edges sensitively.Comment: 36 pages, 20 figures; added discussion on experiments in Sec.VI,
cited Refs.[35]-[40], and reworded Sec.IV
Sedimentary record of coseismic subsidence in Hersek coastal lagoon (Izmit Bay, Turkey) and the late Holocene activity of the North Anatolian Fault
This research was funded by the European Union in the framework of the REL.I.E.F. (Reliable Information on Earthquake Faulting) project (EVG1âCTâ2002â00069). Copyright @ 2011 American Geophysical Union.The late Holocene activity of a restraining bend of the northern strand of the North Anatolian Fault in Izmit Bay was investigated by a sedimentological, geochemical, and paleoecological analysis of sediment cores from Hersek coastal lagoon, NW Turkey. The sediment cores show a succession of sedimentary sequences composed of three units separated by gradual transitions. The first unit is composed of a thin layer of shell debris-rich sediment in abrupt contact with the underlying organic-rich deposits. This unit is over-lain by a thick foraminifera-rich mud deposit, and the sequences are capped by an organic-rich mud unit. These sequences are interpreted as silting up, shallowing upward deposits, typical of a lagoon becoming isolated from the sea. We suggest that they represent the sedimentary signature of coseismic subsidence, which was caused by reverse slip at the Hersek bend, and tsunamis in Izmit Bay. Our radiocarbon-dated paleoseismological record indicates (1) the atypical collapse of the hanging wall during the 740 earthquake and (2) subsidence of the footwall during the 987, 1509, and 1719 earthquakes. This study contributes to the understanding of the dynamics of restraining bends, and it highlights the potential of coastal sediments for reconstructing past earthquakes and tsunamis in regions dominated by strike-slip deformations.This article is available through the Brunel Open Access Publishing Fun
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