23,897 research outputs found
Two-colour QCD at non-zero quark-number density
We have simulated two-colour four-flavour QCD at non-zero chemical potential
for quark number. Simulations were performed on and lattices. Clear evidence was seen for the formation of a colourless diquark
condensate which breaks quark number spontaneously, for . The transition appears to be second order. We have measured the
spectrum of scalar and pseudoscalar bosons which shows clear evidence for the
expected Goldstone boson. Our results are in qualitative agreement with those
from effective Lagrangians for the potential Goldstone excitations of this
theory.Comment: 22 pages RevTeX, 6 figures in 10 postscript file
Observation of Enhanced Beaming from Photonic Crystal Waveguides
We report on the experimental observation of the beaming effect in photonic
crystals enhanced via surface modes. We experimentally map the spatial field
distribution of energy emitted from a subwavelength photonic crystal waveguide
into free-space, rendering with crisp clarity the diffractionless beaming of
energy. Our experimental data agree well with our numerical studies of the
beaming enhancement in photonic crystals with modulated surfaces. Without loss
of generality, we study the beaming effect in a photonic crystal scaled to
microwave frequencies and demonstrate the technological capacity to deliver
long-range, wavelength-scaled beaming of energy.Comment: 4 pages, 6 figure
Effect of pressure on the crystal structure of L-serine-I and the crystal structure of L-serine-II at 5.4 GPa
Bringing remote sensing technology to the user community
The procedures and services available for educating and training potential users of remote sensing technology are discussed along with approaches for achieving an in-house capability for the analysis of remotely sensed data using numerical techniques based on pattern recognition principles. Cost estimates are provided where appropriate
Superconductors from Superstrings
We establish that in a large class of strongly coupled 3+1 dimensional N=1
quiver conformal field theories with gravity duals, adding a chemical potential
for the R-charge leads to the existence of superfluid states in which a chiral
primary operator of the schematic form O = \lambda\lambda + W condenses. Here
\lambda is a gluino and W is the superpotential. Our argument is based on the
construction of a consistent truncation of type IIB supergravity that includes
a U(1) gauge field and a complex scalar.Comment: 5 pages, 2 figures; v2 improved figure, small change
Ultraviolet to infrared emission of z>1 galaxies: Can we derive reliable star formation rates and stellar masses?
We seek to derive star formation rates (SFR) and stellar masses (M_star) in
distant galaxies and to quantify the main uncertainties affecting their
measurement. We explore the impact of the assumptions made in their derivation
with standard calibrations or through a fitting process, as well as the impact
of the available data, focusing on the role of IR emission originating from
dust. We build a sample of galaxies with z>1, all observed from the UV to the
IR (rest frame). The data are fitted with the code CIGALE, which is also used
to build and analyse a catalogue of mock galaxies. Models with different SFHs
are introduced. We define different set of data, with or without a good
sampling of the UV range, NIR, and thermal IR data. The impact of these
different cases on the determination of M_star and SFR are analysed.
Exponentially decreasing models with a redshift formation of the stellar
population z ~8 cannot fit the data correctly. The other models fit the data
correctly at the price of unrealistically young ages when the age of the single
stellar population is taken to be a free parameter. The best fits are obtained
with two stellar populations. As long as one measurement of the dust emission
continuum is available, SFR are robustly estimated whatever the chosen model
is, including standard recipes. M_star measurement is more subject to
uncertainty, depending on the chosen model and the presence of NIR data, with
an impact on the SFR-M_star scatter plot. Conversely, when thermal IR data from
dust emission are missing, the uncertainty on SFR measurements largely exceeds
that of stellar mass. Among all physical properties investigated here, the
stellar ages are found to be the most difficult to constrain and this
uncertainty acts as a second parameter in SFR measurements and as the most
important parameter for M_star measurements.Comment: 14 pages, 14 figures, accepted for publication A&
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