3,899 research outputs found

### Thermoelectric figure of merit of tau-type conductors of several donors

Dimensionless thermoelectric figure of merit $ZT$ is investigated for
two-dimensional organic conductors $\tau-(EDO-S,S-DMEDT-TTF)_2(AuI_2)_{1+y}$,
$\tau$-(EDT-S,S-DMEDT-TTF)_2(AuI_2)_{1+y}$and$\tau$-(P-S,S-DMEDT-TTF)_2(AuI_2)_{1+y}$ ($y \le 0.875$), respectively. The
$ZT$ values were estimated by measuring electrical resistivity, thermopower and
thermal conductivity simultaneously. The largest $ZT$ is 2.7 $\times$ 10$^{-2}$
at 155 K for $\tau-(EDT-S,S-DMEDT-TTF)_2(AuI_2)_{1+y}$, 1.5 $\times$ 10$^{-2}$
at 180 K for $\tau-(EDO-S,S-DMEDT-TTF)_2(AuI_2)_{1+y}$ and 5.4 $\times$
10$^{-3}$ at 78 K for $\tau-(P-S,S-DMEDT-TTF)_2(AuI_2)_{1+y}$, respectively.
Substitution of the donor molecules fixing the counter anion revealed
EDT-S,S-DMEDT-TTF is the best of the three donors to obtain larger $ZT$.Comment: proceedings of ISCOM 2009 (to be published in Physica B

### Bosenova collapse of axion cloud around a rotating black hole

Motivated by possible existence of stringy axions with ultralight mass, we
study the behavior of an axion field around a rapidly rotating black hole (BH)
obeying the sine-Gordon equation by numerical simulations. Due to superradiant
instability, the axion field extracts the rotational energy of the BH and the
nonlinear self-interaction becomes important as the field grows larger. We
present clear numerical evidences that the nonlinear effect leads to a collapse
of the axion cloud and a subsequent explosive phenomena, which is analogous to
the "bosenova" observed in experiments of Bose-Einstein condensate. The
criterion for the onset of the bosenova collapse is given. We also discuss the
reason why the bosenova happens by constructing an effective theory of a
wavepacket model under the nonrelativistic approximation.Comment: 38 pages, 18 figure

### Temperature Chaos and Bond Chaos in the Edwards-Anderson Ising Spin Glass : Domain-Wall Free-Energy Measurements

Domain-wall free-energy $\delta F$, entropy $\delta S$, and the correlation
function, $C_{\rm temp}$, of $\delta F$ are measured independently in the
four-dimensional $\pm J$ Edwards-Anderson (EA) Ising spin glass. The stiffness
exponent $\theta$, the fractal dimension of domain walls $d_{\rm s}$ and the
chaos exponent $\zeta$ are extracted from the finite-size scaling analysis of
$\delta F$, $\delta S$ and $C_{\rm temp}$ respectively well inside the
spin-glass phase. The three exponents are confirmed to satisfy the scaling
relation $\zeta=d_{\rm s}/2-\theta$ derived by the droplet theory within our
numerical accuracy. We also study bond chaos induced by random variation of
bonds, and find that the bond and temperature perturbations yield the universal
chaos effects described by a common scaling function and the chaos exponent.
These results strongly support the appropriateness of the droplet theory for
the description of chaos effect in the EA Ising spin glasses.Comment: 4 pages, 6 figures; The title, the abstract and the text are changed
slightl

### Scaling Analysis of Domain-Wall Free-Energy in the Edwards-Anderson Ising Spin Glass in a Magnetic Field

The stability of the spin-glass phase against a magnetic field is studied in
the three and four dimensional Edwards-Anderson Ising spin glasses. Effective
couplings and effective fields associated with length scale L are measured by a
numerical domain-wall renormalization group method. The results obtained by
scaling analysis of the data strongly indicate the existence of a crossover
length beyond which the spin-glass order is destroyed by field H. The crossover
length well obeys a power law of H which diverges as H goes to zero but remains
finite for any non-zero H, implying that the spin-glass phase is absent even in
an infinitesimal field. These results are well consistent with the droplet
theory for short-range spin glasses.Comment: 4 pages, 5 figures; The text is slightly changed, the figures 3, 4
and 5 are changed, and a few references are adde

### Absolute Transition Probabilities of Lines in the Spectra of Astrophysical Atoms, Molecules, and Ions

Progress in the investigation of absolute transition probabilities (A-values or F values) for ultraviolet lines is reported. A radio frequency ion trap was used for measurement of transition probabilities for intersystem lines seen in astronomical spectra. The intersystem line at 2670 A in Al II, which is seen in pre-main sequence stars and symbiotic stars, was studied

### Absolute absorption cross sections of ozone at 300 K, 228 K and 195 K in the wavelength region 185-240 nm

An account is given of progress of work on absorption cross section measurements of ozone at 300 K, 228 K and 195 K in the wavelength region 185-240 nm. In this wavelength region, the penetration of solar radiation into the Earth's atmosphere is controlled by O2 and O3. The transmitted radiation is available to dissociate trace species such as halocarbons and nitrous oxide. We have recently measured absolute absorption cross sections of O3 in the wavelength region 240-350 nm (Freeman et al., 1985; Yoshino et al., 1988). We apply these proven techniques to the determination of the absorption cross section of O3 at 300 K, 228 K and 195 K throughout the wavelength region 185-240 nm. A paper titled 'Absolute Absorption Cross Section Measurements of Ozone in the Wavelength Region 185-254 nm and the Temperature Dependence' has been submitted for publication in the Journal of Geophysical Research

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