51,484 research outputs found
The FCNC top-squark decay as a probe of squark mixing
In supersymmetry (SUSY) the flavor mixing between top-squark (stop) and
charm-squark (scharm) induces the flavor-changing neutral-current (FCNC) stop
decay . Searching for this decay serves as a
probe of soft SUSY breaking parameters. Focusing on the stop pair production
followed by the FCNC decay of one stop and the charge-current decay of the
other stop, we investigate the potential of detecting this FCNC stop decay at
the Fermilab Tevatron, the CERN Large Hadron Collider (LHC) and the
next-generation linear collider (LC). We find that this decay may not
be accessible at the Tevatron, but could be observable at the LHC and the LC
with high sensitivity.Comment: 13 pages, 3 figures (version to appear in PRD
Experimental test of contextuality in quantum and classical systems
Contextuality is considered as an intrinsic signature of non-classicality,
and a crucial resource for achieving unique advantages of quantum information
processing. However, recently there have been debates on whether classical
fields may also demonstrate contextuality. Here we experimentally configure a
contextuality test for optical fields, adopting various definitions of
measurement events, and analyse how the definitions affect the emergence of
non-classical correlations. The heralded single photon state, a typical
non-classical light field, manifests contextuality in our setup, while
contextuality for classical coherent fields strongly depends on the specific
definition of measurement events which is equivalent to filtering the
non-classical component of the input state. Our results highlight the
importance of definition of measurement events to demonstrate contextuality,
and link the contextual correlations to non-classicality defined by
quasi-probabilities in phase space.Comment: 17 pages, 7 figure
Magic Doping Fractions in High-Temperature Superconductors
We report hole-doping dependence of the in-plane resistivity \rho_{ab} in a
cuprate superconductor La_{2-x}Sr_{x}CuO_{4}, carefully examined using a series
of high-quality single crystals. Our detailed measurements find a tendency
towards charge ordering at particular rational hole doping fractions of 1/16,
3/32, 1/8, and 3/16. This observation appears to suggest a specific form of
charge order and is most consistent with the recent theoretical prediction of
the checkerboard-type ordering of the Cooper pairs at rational doping fractions
x = (2m+1)/2^n, with integers m and n.Comment: 5 pages, 3 figure, resubmitted to Phys. Rev. Lett. The Tc vs. x
diagram has been added and the discussions have been modified to focus more
on the experimental result
Extension of Loop Quantum Gravity to Metric Theories beyond General Relativity
The successful background-independent quantization of Loop Quantum Gravity
relies on the key observation that classical General Relativity can be cast
into the connection-dynamical formalism with the structure group of SU(2). Due
to this particular formalism, Loop Quantum Gravity was generally considered as
a quantization scheme that applies only to General Relativity. However, we will
show that the nonperturbative quantization procedure of Loop Quantum Gravity
can be extended to a rather general class of metric theories of gravity, which
have received increased attention recently due to motivations coming form
cosmology and astrophysics. In particular, we will first introduce how to
reformulate the 4-dimensional metric theories of gravity, as well as
Brans-Dicke theory, into connection-dynamical formalism with real SU(2)
connections as configuration variables. Through these formalisms, we then
outline the nonpertubative canonical quantization of the theories and
Brans-Dicke theory by extending the loop quantization scheme of General
Relativity.Comment: 10 pages; Proceedings of Loops'11, Madrid, submitted to Journal of
Physics: Conference Serie
Effects of geogrid encasement on lateral and vertical deformations of stone columns in model tests
Geosynthetic encasement of individual stone columns can provide additional confinement to the columns thus increasing their load capacities and reducing lateral and vertical deformations. Most of past studies have been focused on the load capacities and settlements (i.e. vertical deformations) of the encased stone columns. However, the load transfer mechanism and the lateral bulging deformation pattern of the encased stone columns are not thoroughly understood. In the present study, four series of laboratory model tests in a large-scale testing tank were performed to investigate the effect of geogrid encasement on the lateral and vertical deformations of stone columns installed in a clay bed. For comparison purposes, ordinary stone columns were also tested and evaluated. The main objective of this research is to investigate the lateral and vertical deformation patterns of the encased stone columns and the reinforcement mechanisms of the geogrid encasement with different encasement lengths. In addition, the stress–strain characteristics of the encasement were measured and analysed. The test results show that the ultimate load capacity of the soft soil was greatly increased by the geogrid-encased stone columns. The effective length of the encasement was three to four times of the diameter of stone columns based on the consideration of performance and economy. In comparison with the analytical solution based on the unit cell concept with full encasement of columns, the experimental tests on composite foundations with partially encased columns, which allowed lateral deformations of columns and soils and slippage along the column-soil interfaces (geogrid–soil, stone column–geogrid, and stone column–soil if the column is not encased), resulted in larger settlements, especially at higher vertical pressures
Toxicokinetic behaviors and modes of perfluorooctane sulfonate (PFOS) and perfluorooctane acid (PFOA) on tilapia (Oreochromis niloticus)
Perfluorooctane sulfonate (PFOS) and perfluorooctane acid (PFOA) are widely distributed environmentally persistent organic pollutants found at low levels in human and wildlife ecosystem. The objectives of the current study were to investigate toxicokinetic behaviors and modes of PFOS and PFOA on tilapia (Oreochromis niloticus). The toxicokinetic behaviors and modes of PFOS and PFOA are different in tilapia during experimental periods. Exposure to both PFOS and PFOA was approximately 5 to 6 times higher for male tilapia than for female tilapia. The terminal half-life of PFOA in serum was about 4 times longer for male tilapia than for female tilapia. The apparent volume of distribution for PFOS and PFOA in the serum was about 3 to 4 times higher for female tilapia than for male tilapia. The lymphocytes level decreased rapidly with the increased PFOA concentration. A similar pattern was observed with the PFOS exposure, and it is remarkable that PFOS and PFOA were significantly accumulated in both PFOS and PFOA exposure but PFOA showed a greater effect than PFOS. PFOA blood concentrations were lesser than the limit of quantification in non-exposure tilapia during an uptake period, while measured PFOS concentrations were at least six times lesser than those in PFOS exposure. Tilapia weight gain was also decreased with statistical significance in all PFOA-treated groups, and the effect of PFOA was higher than that of PFOS. The effects of PFOA in survival percent were more pronounced in this case than that of PFOS. Moreover, PFOA had similar mode, and PFOS and PFOA can inhibit the 17β-HSD3 enzyme activity of tilapia.Key words: Toxicokinetic, behaviors, perfluorooctane sulfonate (PFOS), perfluorooctane acid (PFOA), tilapia (Oreochromis niloticus)
Asymptotics of Spinfoam Amplitude on Simplicial Manifold: Lorentzian Theory
The present paper studies the large-j asymptotics of the Lorentzian EPRL
spinfoam amplitude on a 4d simplicial complex with an arbitrary number of
simplices. The asymptotics of the spinfoam amplitude is determined by the
critical configurations. Here we show that, given a critical configuration in
general, there exists a partition of the simplicial complex into three type of
regions R_{Nondeg}, R_{Deg-A}, R_{Deg-B}, where the three regions are
simplicial sub-complexes with boundaries. The critical configuration implies
different types of geometries in different types of regions, i.e. (1) the
critical configuration restricted into R_{Nondeg} is degenerate of type-A in our definition of degeneracy, but implies
a nondegenerate discrete Euclidean geometry on R_{Deg-A}, (3) the critical
configuration restricted into R_{Deg-B} is degenerate of type-B, and implies a
vector geometry on R_{Deg-B}. With the critical configuration, we further make
a subdivision of the regions R_{Nondeg} and R_{Deg-A} into sub-complexes (with
boundary) according to their Lorentzian/Euclidean oriented 4-simplex volume
V_4(v), such that sgn(V_4(v)) is a constant sign on each sub-complex. Then in
the each sub-complex, the spinfoam amplitude at the critical configuration
gives the Regge action in Lorentzian or Euclidean signature respectively on
R_{Nondeg} or R_{Deg-A}. The Regge action reproduced here contains a sign
factor sgn(V_4(v)) of the oriented 4-simplex volume. Therefore the Regge action
reproduced here can be viewed a discretized Palatini action with on-shell
connection. Finally the asymptotic formula of the spinfoam amplitude is given
by a sum of the amplitudes evaluated at all possible critical configurations,
which are the products of the amplitudes associated to different type of
geometries.Comment: 54 pages, 2 figures, reference adde
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