4,394 research outputs found

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

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    It is mentioned that anyon thermodynamic potential Q(α,N)Q(\alpha, N) could not be factorized in terms characteristic of the ideal boson α=0\alpha =0 and fermion α=1\alpha =1 gases by the relation Q(α,N)=(1α)Q(0,Nb)+αQ(1,Nf)Q(\alpha, N) = (1-\alpha) Q(0, N_b)+ \alpha Q(1, N_f) in which N=Nf+NbN=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(α)=αQ(1)+(1α)Q(0)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

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    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

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    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

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    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 VR5V\sim R^5, with an entropy S=83SBHS = \frac{8}{3}S_{BH}.Comment: 5 pages, no figures, to be published in Phys. Lett.

    Naked Singularity Explosion

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    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? --

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    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

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    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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