4,394 research outputs found

### Comment on ``Quantum Statistical Mechanics of an Ideal Gas with Fractional Exclusion Statistics in Arbitrary Dimension"

It is mentioned that anyon thermodynamic potential $Q(\alpha, N)$ could not
be factorized in terms characteristic of the ideal boson $\alpha =0$ and
fermion $\alpha =1$ gases by the relation $Q(\alpha, N) = (1-\alpha) Q(0, N_b)+
\alpha Q(1, N_f)$ in which $N=N_f +N_b$, that claimed in Phys. Rev. Lett. 78,
3233 (1997). Our analyses indicate that the thermodynamic quantities of anyon
gas may be factorized as $Q(\alpha) = \alpha Q(1) + (1-\alpha) Q(0)$ only in
the two-dimension system

### Relaxor ferroelectricity induced by electron correlations in a molecular dimer Mott insulator

We have investigated the dielectric response in an antiferromagnetic
dimer-Mott insulator beta'-(BEDT-TTF)2ICl2 with square lattice, compared to a
spin liquid candidate kappa-(BEDT-TTF)2Cu2(CN)3. Temperature dependence of the
dielectric constant shows a peak structure obeying Curie-Weiss law with strong
frequency dependence. We found an anisotropic ferroelectricity by pyrocurrent
measurements, which suggests the charge disproportionation in a dimer. The
ferroelectric actual charge freezing temperature is related to the
antiferromagnetic interaction, which is expected to the charge-spin coupled
degrees of freedom in the system.Comment: 5 pages, 4 figures, to be published in Phys. Rev.

### Impurity-doping induced ferroelectricity in frustrated antiferromagnet CuFeO2

Dielectric responses have been investigated on the triangular-lattice
antiferromagnet CuFeO2 and its site-diluted analogs CuFe1-xAlxO2 (x=0.01 and
0.02) with and without application of magnetic field. We have found a
ferroelectric behavior at zero magnetic field for x=0.02. At any doping level,
the onset field of the ferroelectricity always coincides with that of the
noncollinear magnetic structure while the transition field dramatically
decreases to zero field with Al doping. The results imply the further
possibility of producing the ferroelectricity by modifying the frustrated spin
structure in terms of site-doping and external magnetic field.Comment: 4 pages, 4 figure

### Black hole horizons can hide positive heat capacity

Regarding the volume as independent thermodynamic variable we point out that
black hole horizons can hide positive heat capacity and specific heat. Such
horizons are mechanically marginal, but thermally stable. In the absence of a
canonical volume definition, we consider various suggestions scaling
differently with the horizon radius. Assuming Euler-homogeneity of the entropy,
besides the Hawking temperature, a pressure and a corresponding work term
render the equation of state at the horizon thermally stable for any meaningful
volume concept that scales larger than the horizon area. When considering also
a Stefan--Boltzmann radiation like equation of state at the horizon, only one
possible solution emerges: the Christodoulou--Rovelli volume, scaling as $V\sim
R^5$, with an entropy $S = \frac{8}{3}S_{BH}$.Comment: 5 pages, no figures, to be published in Phys. Lett.

### Naked Singularity Explosion

It is known that the gravitational collapse of a dust ball results in naked
singularity formation from an initial density profile which is physically
reasonable. In this paper, we show that explosive radiation is emitted during
the formation process of the naked singularity.Comment: 6 pages, 3 figures, Accepted for Publication in Phys. Rev. D as a
Rapid Communicatio

### Physical aspects of naked singularity explosion - How does a naked singularity explode? --

The behaviors of quantum stress tensor for the scalar field on the classical
background of spherical dust collapse is studied. In the previous works
diverging flux of quantum radiation was predicted. We use the exact expressions
in a 2D model formulated by Barve et al. Our present results show that the back
reaction does not become important during the semiclassical phase. The
appearance of the naked singularity would not be affected by this quantum field
radiation. To predict whether the naked singularity explosion occurs or not we
need the theory of quantum gravity. We depict the generation of the diverging
flux inside the collapsing star. The quantum energy is gathered around the
center positively. This would be converted to the diverging flux along the
Cauchy horizon. The ingoing negative flux crosses the Cauchy horizon. The
intensity of it is divergent only at the central naked singularity. This
diverging negative ingoing flux is balanced with the outgoing positive
diverging flux which propagates along the Cauchy horizon. After the replacement
of the naked singularity to the practical high density region the instantaneous
diverging radiation would change to more milder one with finite duration.Comment: 18 pages, 16 figure

### Performance Measurements of 8-Gsps 1-bit ADCs Developed for Wideband Radio Astronomical Observations

8-Gsps 1-bit Analog-to-Digital Converters (ADCs) were newly developed toward
the realization of the wideband observation. The development of the wideband
ADCs is one of the most essential developments for the radio interferometer. To
evaluate its performance in interferometric observations, the time (phase)
stability and frequency response were measured with a noise source and a signal
generator. The results of these measurements show that the developed ADCs can
achieve the jitter time less than 0.05 psec at the time interval of 1 sec, the
passband frequency response with the slope less than 0.73 dB/GHz and the ripple
less than 1.8 dB, and the aperture time less than 20 psec. The details of the
developed ADC design, the measurement methods, and the results of these
measurements are presented in this paper.Comment: Accepted for publication in PASJ. 19 pages, 15 figure

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