851 research outputs found
Level spectroscopy of the square-lattice three-state Potts model with a ferromagnetic next-nearest-neighbor coupling
We study the square-lattice three-state Potts model with the ferromagnetic
next-nearest-neighbor coupling at finite temperature. Using the
level-spectroscopy method, we numerically analyze the excitation spectrum of
the transfer matrices and precisely determine the global phase diagram. Then we
find that, contrary to a previous result based on the finite-size scaling, the
massless region continues up to the decoupling point with criticality in the antiferromagnetic region. We also check the universal
relations among excitation levels to provide the reliability of our result.Comment: 4 pages, 2 figure
History Memorized and Recalled upon Glass Transition
The memory effect upon glassification is studied in the glass to rubber
transition of vulcanized rubber with the strain as a controlling parameter. A
phenomenological model is proposed taking the history of the temperature and
the strain into account, by which the experimental results are interpreted. The
data and the model demonstrate that the glassy state memorizes the time-course
of strain upon glassification, not as a single parameter but as the history
itself. The data also show that the effect of irreversible deformation in the
glassy state is beyond the scope of the present model.
Authors' remark: The title of the paper in the accepted version is above. The
title appeared in PRL is the one changed by a Senior Assistant Editor after
acceptance of the paper. The recovery of the title was rejected in the
correction process.Comment: 4 pages, 4 figure
Black hole radiation with high frequency dispersion
We consider one model of a black hole radiation, in which the equation of
motion of a matter field is modified to cut off high frequency modes. The
spectrum in the model has already been analytically derived in low frequency
range, which has resulted in the Planckian distributin of the Hawking
temperature. On the other hand, it has been numerically shown that its spectrum
deviates from the thermal one in high frequency range. In this paper, we
analytically derive the form of the deviation in the high frequency range. Our
result can qualitatively explain the nature of the numerically calculated
spectrum. The origin of the deviation is clarified by a simple discussion.Comment: 9 pages, 10 figures, submitted to Phys.Rev.
Origami-based impact mitigation via rarefaction solitary wave creation
The principles underlying the art of origami paper folding can be applied to
design sophisticated metamaterials with unique mechanical properties. By
exploiting the flat crease patterns that determine the dynamic folding and
unfolding motion of origami, we are able to design an origami-based
metamaterial that can form rarefaction solitary waves. Our analytical,
numerical and experimental results demonstrate that this rarefaction solitary
wave overtakes initial compressive strain waves, thereby causing the latter
part of the structure to feel tension first instead of compression. This
counter-intuitive dynamic mechanism can be used to create a highly
efficient--yet reusable--impact mitigating system without relying on material
damping, plasticity or fracture
Finite-size-scaling ansatz for the helicity modulus of the triangular-lattice three-spin interaction model
The Berezinskii-Kosterlitz-Thouless-type continuous phase transition observed
in the three-spin interaction model is discussed. The relevant field theory
describes the topological defects involved and enables us to perform the
renormalization-group analysis. Based on it, we shall propose the
finite-size-scaling ansatz for the helicity modulus which exhibits the exponent
for the correlation length in the disordered phase. We perform
the Monte Carlo simulations to confirm the ansatz. Also, we argue its relevance
to the ground-state phase transition in the quantum spin chain.Comment: 5 pages, 4 figure
Black holes and a scalar field in an expanding universe
We consider a model of an inhomogeneous universe including a massless scalar
field, where the inhomogeneity is assumed to consist of many black holes. This
model can be constructed by following Lindquist and Wheeler, which has already
been investigated without including scalar field to show that an averaged scale
factor coincides with that of the Friedmann model. In this work we construct
the inhomogeneous universe with an massless scalar field, where we assume that
the averaged scale factor and scalar field are given by those of the Friedmann
model including a scalar field. All of our calculations are carried out in the
framework of Brans-Dicke gravity. In constructing the model of an inhomogeneous
universe, we define the mass of a black hole in the Brans-Dicke expanding
universe which is equivalent to ADM mass if the mass evolves adiabatically, and
obtain an equation relating our mass to the averaged scalar field and scale
factor. As the results we find that the mass has an adiabatic time dependence
in a sufficiently late stage of the expansion of the universe, and that the
time dependence is qualitatively diffenrent according to the sign of the
curvature of the universe: the mass increases decelerating in the closed
universe case, is constant in the flat case and decreases decelerating in the
open case. It is also noted that the mass in the Einstein frame depends on
time. Our results that the mass has a time dependence should be retained even
in the general scalar-tensor gravitiy with a scalar field potential.
Furthermore, we discuss the relation of our results to the uniqueness theorem
of black hole spacetime and gravitational memory effect.Comment: 16 pages, 3 tables, 5 figure
On the Limits of Analogy Between Self-Avoidance and Topology-Driven Swelling of Polymer Loops
The work addresses the analogy between trivial knotting and excluded volume
in looped polymer chains of moderate length, , where the effects of
knotting are small. A simple expression for the swelling seen in trivially
knotted loops is described and shown to agree with simulation data. Contrast
between this expression and the well known expression for excluded volume
polymers leads to a graphical mapping of excluded volume to trivial knots,
which may be useful for understanding where the analogy between the two
physical forms is valid. The work also includes description of a new method for
the computational generation of polymer loops via conditional probability.
Although computationally intensive, this method generates loops without
statistical bias, and thus is preferable to other loop generation routines in
the region .Comment: 10 pages, 5 figures, supplementary tex file and datafil
Pengukuran Resistivitas Bahan Organik Superkonduktor β'-(BEDT-TTF)2ICl2 Dengan Metode Four Point Probe
Telah dilakukan pembuatan kristal β'-(BEDT-TTF)2ICl2 dengan proses elektro sintesis kimia selama 8 hari. Proses elektrolisis ini dilakukan di dalam incubator dengan arus 1.5 μA. Kristal yang dihasilkan berwarana hitam memanjang . Kristal ini bersifat bahan organik metal dimana BEDT-TTF sebagai kation dan ICl2 sebagai anion. Selanjutnya kristal ini dilakukan pengukuran resistivitas dengan menggunakan metode four point probe. Metode ini menggunakan kawat emas (Au) sebagai probe, dua probe sebagai sumber arus dan 2 probe lainya sebagai pengukur beda potensial. Hasil karakterisasi menunjukan penambahan resistivitas sesuai dengan penurunan temperatur. Hal ini dikibatkan pengaruh dari β', sehingga kristal ini memiliki bentuk satu dimensi. Oleh sebab itu kristal β'-(BEDT-TTF)2ICl2 ini bersifat antiferromagnetik insulator (Mott Insulator)
Black Hole Evaporation in an Expanding Universe
We calculate the quantum radiation power of black holes which are asymptotic
to the Einstein-de Sitter universe at spatial and null infinities. We consider
two limiting mass accretion scenarios, no accretion and significant accretion.
We find that the radiation power strongly depends on not only the asymptotic
condition but also the mass accretion scenario. For the no accretion case, we
consider the Einstein-Straus solution, where a black hole of constant mass
resides in the dust Friedmann universe. We find negative cosmological
correction besides the expected redshift factor. This is given in terms of the
cubic root of ratio in size of the black hole to the cosmological horizon, so
that it is currently of order but could have been significant at the formation epoch of
primordial black holes. Due to the cosmological effects, this black hole has
not settled down to an equilibrium state. This cosmological correction may be
interpreted in an analogy with the radiation from a moving mirror in a flat
spacetime. For the significant accretion case, we consider the Sultana-Dyer
solution, where a black hole tends to increase its mass in proportion to the
cosmological scale factor. In this model, we find that the radiation power is
apparently the same as the Hawking radiation from the Schwarzschild black hole
of which mass is that of the growing mass at each moment. Hence, the energy
loss rate decreases and tends to vanish as time proceeds. Consequently, the
energy loss due to evaporation is insignificant compared to huge mass accretion
onto the black hole. Based on this model, we propose a definition of
quasi-equilibrium temperature for general conformal stationary black holes.Comment: Accepted for publication in Class.Quant.Grav., 18 pages and 3 figure
Monte Carlo study of the antiferromagnetic three-state Potts model with staggered polarization field on the square lattice
Using the Wang-Landau Monte Carlo method, we study the antiferromagnetic (AF)
three-state Potts model with a staggered polarization field on the square
lattice. We obtain two phase transitions; one belongs to the ferromagnetic
three-state Potts universality class, and the other to the Ising universality
class. The phase diagram obtained is quantitatively consistent with the
transfer matrix calculation. The Ising transition in the large nearest-neighbor
interaction limit has been made clear by the detailed analysis of the energy
density of states.Comment: accepted for publication in J. Phys.
- …