3,366 research outputs found
Surface core excitons in III-V semiconductors
Recent experiments have shown that the cation core excitons
on the (110) surface of many III-V semiconductors have very
large binding energies.(^1) They are sometimes reported to be bound by as much as ≳0.8 eV, tightly bound compared to
bulk binding energies of ≾0.1 eV. To explore this phenomenon, we have calculated the binding energies and oscillator strengths of core excitons on the (110) surface of GaAs, GaSb, GaP, and InP
Structure and management issues of the emerging ornamental fish trade in Eritrea
Following independence from Ethiopia in 1993, Eritrea resumed exploiting Red Sea and Arabian fish species for the ornamental trade in 1995 as a means to earn foreign exchange from sparsely exploited marine resources. This paper describes the findings of research conducted in 1997, in collaboration with the Eritrean Ministry of Fisheries. The capture, transport and export of aquarium fish were reviewed and potential impacts and the status of management were investigated through liaison with stakeholders and researchers. From 1995 to 1997 two companies exported approximately 60,000 fish per year, mainly to the USA, worth US$65,000 (export value). Seventyfive species (from 22 families) were exported. Damselfishes made up two-thirds of total exports but more valuable families (angelfishes and butterflyfishes) were more economically significant. To earn revenue for Eritrea, a 20% export tax was imposed, although this was calculated from declarations by the operators. The emerging nature of the trade allowed detailed monitoring by the Ministry of Fisheries. However, management efforts were constrained by a lack of capacity for enforcement and baseline research. Several potential effects of the trade exist but other, land-based impacts may be more pressing concerns for Eritrea’s reefs. Research priorities for management are discussed as well as the implications of mariculture of Eritrean species by other nations
Quantum phase diagrams of fermionic dipolar gases for an arbitrary orientation of dipole moment in a planar array of 1D tubes
We systematically study ground state properties of fermionic dipolar gases in
a planar array of one-dimensional potential tubes for an arbitrary orientation
of dipole moments. Using the Luttinger liquid theory with the generalized
Bogoliubov transformation, we calculate the elementary excitations and the
Luttinger scaling exponents for various relevant quantum orders. The complete
quantum phase diagrams for arbitrary polar angle of the dipole moment is
obtained, including charge density wave, p-wave superfluid, inter-tube
gauge-phase density wave, and inter-tube s-wave superfluid, where the last two
breaks the U(1) gauge symmetry of the system (conservation of particle number
in each tube) and occurs only when the inter-tube interaction is larger than
the intra-tube interaction. We then discuss the physical properties of these
many-body phases and their relationship with some solid state systems.Comment: 10 pages and 10 figure
A method for characterization of coherent backgrounds in real time and its application in gravitational wave data analysis
Many experiments, and in particular gravitational wave detectors, produce
continuous streams of data whose frequency representations contain discrete,
relatively narrowband coherent features at high amplitude. We discuss the
application of digital Fourier transforms (DFTs) to characterization of these
features, hereafter frequently referred to as lines. Application of DFTs to
continuously produced time domain data are achieved through an algorithm
hereafter referred to as EFC for efficient time-domain determination of the
Fourier coefficients of a data set. We first define EFC and discuss parameters
relating to the algorithm that determine its properties and action on the data.
In gravitational wave interferometers, these lines are commonly due to
parasitic sources of coherent background interference coupling into the
instrument. Using GEO 600 data, we next demonstrate that time domain
subtraction of lines can proceed without detrimental effects either on features
at frequencies separated from that of the subtracted line, or on features at
the frequency of the line but having different stationarity properties.Comment: 15 pages, 7 figures, 1 table. Accepted by Classical and Quantum
Gravit
Mean field baryon magnetic moments and sumrules
New developments have spurred interest in magnetic moments (-s) of
baryons. The measurement of some of the decuplet -s and the findings of
new sumrules from various methods are partly responsible for this renewed
interest. Our model, inspired by large colour approximation, is a relativistic
self consistent mean field description with a modified Richardson potential and
is used to describe the -s and masses of all baryons with up (u), down (d)
and strange (s) quarks. We have also checked the validity of the Franklin
sumrule (referred to as CGSR in the literature) and sumrules of Luty,
March-Russell and White. We found that our result for sumrules matches better
with experiment than the non-relativistic quark model prediction. We have also
seen that quark magnetic moments depend on the baryon in which they belong
while the naive quark model expects them to be constant.Comment: 7 pages, no figure, uses epl.cl
Interaction-induced first order correlation between spatially-separated 1D dipolar fermions
We calculate the ground-state properties of fermionic dipolar atoms or
molecules in a one-dimensional double-tube potential by using the Luttinger
liquid theory and the density matrix renormalization-group calculation. When
the external field is applied near a magic angle with respect to the
double-tube plane, the long-ranged dipolar interaction can generate a
spontaneous correlation between fermions in different tubes, even when the bare
intertube tunneling rate is negligibly small. Such interaction-induced
correlation strongly enhances the contrast of the interference fringes and
therefore can be easily observed in the standard time-of-flight experiment.Comment: Same as the published versio
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