1,025 research outputs found
Paramagnetic Faraday rotation with spin-polarized ytterbium atoms
We report observation of the paramagnetic Faraday rotation of spin-polarized
ytterbium (Yb) atoms. As the atomic samples, we used an atomic beam, released
atoms from a magneto-optical trap (MOT), and trapped atoms in a
far-off-resonant trap (FORT). Since Yb is diamagnetic and includes a spin-1/2
isotope, it is an ideal sample for the spin physics, such as quantum
non-demolition measurement of spin (spin QND), for example. From the results of
the rotation angle, we confirmed that the atoms were almost perfectly
polarized.Comment: 8 pages, 20 figure
Chemically sector-zoned garnets in the metapelitic rocks of the Silgará Formation in the central Santander Massif, colombian andes: occurrence and growth history
Almandine-rich garnet in the Silgará Formation metapelitic rocks in the central Santander Massif usually shows concentric normal chemical zoning. However, different types of garnet zoning have been reported, including chemically sector-zoned garnet, which is described here. Recent studies reveal additional discoveries of this type of zoning in different localities. Textural sector-zoned garnets have been observed in the staurolite-kyanite metamorphic zone of the Silgará Formation. They are generally fine-grained (0.25-2.00 mm in diameter), and occur in quartz-rich bands with other textural types of garnet (skeletal and poikiloblastic). The study of the chemically sector-zoned garnet indicates that it has grown in the latest stage of the Silgará Formation metamorphism, during the emplacement of orthogneiss masses. Studies on garnet from the Silgará Formation pelitic rocks have shown the importance of this as a key piece for interpretation of the tectono-metamorphic history of this metamorphic unit.El granate tipo almandino en las rocas metapelíticas de la Formación Silgará en la región central del Macizo de Santander usualmente muestra zonación química concéntrica normal. Sin embargo, se han reportado diferentes tipos de zonación en el granate, incluyendo el granate químicamente sector-zonado, el cual es descrito aquí. Estudios recientes revelan descubrimientos adicionales de este tipo de zonación en diferentes localidades. Los granates que exhiben zonación sectorial textural han sido observados en la zona metamórfica de la estaurolitacianita de la Formación Silgará. Estos son generalmente de grano fino (0.25-2.00 mm de diámetro), y ocurren en bandas ricas en cuarzo junto con otros tipos texturales de granate (esqueletal y poiquiloblástico). El estudio del granate químicamente sector-zonado indica que este creció en la etapa tardía de metamorfismo de la Formación Silgará, durante el emplazamiento de masas de ortoneis. Estudios sobre el granate en las rocas pelíticas de la Formación Silgará han mostrado su importancia como pieza clave en la interpretación de la historia tectonometamórfica de esta unidad metamórfica.
 
Bose-Einstein Condensation in the Relativistic Ideal Bose Gas
The Bose-Einstein condensation (BEC) critical temperature in a relativistic
ideal Bose gas of identical bosons, with and without the antibosons expected to
be pair-produced abundantly at sufficiently hot temperatures, is exactly
calculated for all boson number-densities, all boson point rest masses, and all
temperatures. The Helmholtz free energy at the critical BEC temperature is
found to be lower, thus implying that the omission of antibosons always leads
to the computation of a metastable state.Comment: 10 pages, 4 figure
Beyond pairs: definition and interpretation of third-order structure in spatial point patterns
Spatial distributions of biological species are an important source of information for understanding local interactions at the scale of individuals. Technological advances have made it easier to measure these distributions as spatial point patterns, specifying the locations of individuals. Extensive attention has been devoted to analyzing the second-order structure of such point patterns by focusing on pairs of individuals, and it is well known that the local crowdedness of individuals can thus be quantified. Statistical measures such as a point pattern's pair correlation function or Ripley's K function show whether a given point pattern is clustered (excess of short-distance pairs) or overdispersed (shortage of short-distance pairs). These notions are naturally defined in comparison with control patterns exhibiting complete spatial randomness, i.e., an absence of any spatial structure. However, here is no rational reason why the analysis of point patterns should stop at the second order. In this paper, we focus on triplets of individuals in an attempt to quantify and interpret the third-order structure of a point pattern. We demonstrate that point patterns with 'bandedness', in which individuals are primarily distributed within bands, can be detected by an excess of thinner triplets at a characteristic spatial scale linked to the band's width. In this context, we show how the generation of control patterns as a reference for gauging a test pattern's triplet frequencies is critical for defining and interpreting the third-order structure of point patterns. Since perfect information on a point pattern's second-order structure typically suffices for its unique reconstruction (up to translation, rotation, and reflection), we conjecture that it is essential to minimally coarse-grain such second-order information before using it to generate control patterns for identifying a point pattern's third-order structure. We recommend the further exploration of this conjecture for future studies
Green's function of fully anharmonic lattice vibration
Motivated by the discovery of superconductivity in beta-pyrochlore oxides, we
study property of rattling motion coupled with conduction electrons. We derive
the general expression of the Green's function of fully anharmonic lattice
vibration within the accuracy of the second order perturbation of electron-ion
interaction by introducing self-energy, vertex-correction, and normalization
factor for each transition. Using the expression, we discuss the characteristic
properties of the spectral function in the entire range from weakly anharmonic
potential to double-well case, and calculate NMR relaxation rate due to the two
phonon Raman process
Suppression and Control of Pre-thermalization in Multi-component Fermi Gases Following a Quantum Quench
We investigate the mechanisms of control and suppression of
pre-thermalization in -component alkaline earth gases. To this end, we
compute the short-time dynamics of the instantaneous momentum distribution and
the relative population for different initial conditions after an interaction
quench, accounting for the 11 peffect of initial interactions. We find that
switching on an interaction that breaks the SU symmetry of the initial
Hamiltonian, thus allowing for the occurrence of spin-changing collisions, does
not necessarily lead to a suppression of pre-thermalization. However, the
suppression will be most effective in the presence of SU-breaking
interactions provided the number of components and the initial state
contains a population imbalance that breaks the SU symmetry. We also find
the conditions on the imbalance initial state that allow for a pre-thermal
state to be stabilized for a certain time. Our study highlights the important
role played by the initial state in the pre-thermalization dynamics of
multicomponent Fermi gases. It also demonstrates that alkaline-earth Fermi
gases provide an interesting playground for the study and control of
pre-thermalization.Comment: 11 pages, 8 figure
A case of Autoimmune-related Pancreatitis - Usefulness of Fluorodeoxyglucose Positron Emission Tomography for the Evaluation of the Effect of Steroid Therapy -
開始ページ、終了ページ: 冊子体のページ付
The Tokyo Axion Helioscope Experiment
A preliminary result of the solar axion search experiment at the University
of Tokyo is presented. We searched for axions which could be produced in the
solar core by exploiting the axion helioscope. The helioscope consists of a
superconducting magnet with field strength of 4 Tesla over 2.3 meters. From the
absence of the axion signal we set a 95 % confidence level upper limit on the
axion coupling to two photons for the axion mass eV. This is the first solar axion
search experiment whose sensitivity to exceeds the limit
inferred from the solar age consideration.Comment: 5 pages, 5 eps files included, uses espcrc2.sty, to be published in
Proc. AXION WORKSHOP, Gainesville, Florida, 13-15 March 1998, ed. by
P.Sikivi
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