8,872 research outputs found
Thermodynamic cost of reversible computing
Since reversible computing requires preservation of all information
throughout the entire computational process, this implies that all errors that
appear as a result of the interaction of the information-carrying system with
uncontrolled degrees of freedom must be corrected. But this can only be done at
the expense of an increase in the entropy of the environment corresponding to
the dissipation, in the form of heat, of the ``noisy'' part of the system's
energy.
This paper gives an expression of that energy in terms of the effective noise
temperature, and analyzes the relationship between the energy dissipation rate
and the rate of computation. Finally, a generalized Clausius principle based on
the concept of effective temperature is presented.Comment: 5 pages; added two paragraphs and fixed a number of typo
Structures and Electromagnetic Properties of New Metal-Ordered Manganites; RBaMn_{2}O_{6} (R = Y and Rare Earth Elements)
New metal-ordered manganites RBaMn_{2}O_{6} have been synthesized and
investigated in the structures and electromagnetic properties. RBaMn_{2}O_{6}
can be classified into three groups from the structural and electromagnetic
properties. The first group (R = La, Pr and Nd) has a metallic ferromagnetic
transition, followed by an A-type antiferromagnetic transition in
PrBaMn_{2}O_{6}. The second group (R = Sm, Eu and Gd) exhibits a charge-order
transition, followed by an antiferromagnetic long range ordering. The third
group (R = Tb, Dy and Ho) shows successive three phase transitions, the
structural, charge/orbital-order and magnetic transitions, as observed in
YBaMn_{2}O_{6}. Comparing to the metal-disordered manganites
(R^{3+}_{0.5}A^{2+}_{0.5})MnO_{3}, two remarkable features can be recognized in
RBaMn_{2}O_{6}; (1) relatively high charge-order transition temperature and (2)
the presence of structural transition above the charge-order temperature in the
third group. We propose a possible orbital ordering at the structural
transition, that is a possible freezing of the orbital, charge and spin degrees
of freedom at the independent temperatures in the third group. These features
are closely related to the peculiar structure that the MnO_{2} square-lattice
is sandwiched by the rock-salt layers of two kinds, RO and BaO with extremely
different lattice-sizes.Comment: 5 pages, 4 figures, submitted to J. Phys. Soc. Jp
Deterministic Quantum Key Distribution Using Gaussian-Modulated Squeezed States
A continuous variable ping-pong scheme, which is utilized to generate
deterministically private key, is proposed. The proposed scheme is implemented
physically by using Gaussian-modulated squeezed states. The deterministic way,
i.e., no basis reconciliation between two parties, leads a two-times efficiency
comparing to the standard quantum key distribution schemes. Especially, the
separate control mode does not need in the proposed scheme so that it is
simpler and more available than previous ping-pong schemes. The attacker may be
detected easily through the fidelity of the transmitted signal, and may not be
successful in the beam splitter attack strategy.Comment: 7 pages, 4figure
Octupolar order in the multiple spin exchange model on a triangular lattice
We show how a gapless spin liquid with hidden octupolar order arises in an
applied magnetic field, in a model applicable to thin films of 3He with
competing ferromagnetic and antiferromagnetic (cyclic) exchange interactions.
Evidence is also presented for nematic -- i.e., quadrupolar -- correlations
bordering on ferromagnetism in the absence of a magnetic field.Comment: 4 pages, 5 figure
D-brane width
Loop quantum gravity predicts that there are non-zero minimal area, and
non-zero minimal volume in (3+1) dimensions. Given this, one can easily guess
that one will have a non-zero minimal 9-volume in (9+1) dimensions. Therefore,
in this paper, we argue that not only D9-brane but also Dp-brane for p less
than 9 has a 9-volume. This idea is new, as the present view states that such a
Dp-brane has p-volume but no 9 volume. To demonstrate this, first, we equate
D8-brane action with D9-brane action and show that 9th direction which is
perpendicular to D8-brane has non-zero width. We repeat this step for different
ps; we equate Dp-brane action with Dp-1 brane action. By this iteration and
induction we conclude that Dp-brane has non-zero widths for each of (9-p)
directions perpendicular to the Dp-brane, and therefore, non-zero volume. When
antisymmetric tensor and field strength are zero, this width is calculated to
be 2 pi sqrt(alpha') for all (9-p) directions. For non-vanishing antisymmetric
tensor and field strength, the width receives small corrections. In this paper,
we only calculate up to the first order correction.Comment: 4 pages, no figures, argument based on loop quantum gravity adde
Isolated Eigenvalues of the Ferromagnetic Spin-J XXZ Chain with Kink Boundary Conditions
We investigate the low-lying excited states of the spin J ferromagnetic XXZ
chain with Ising anisotropy Delta and kink boundary conditions. Since the third
component of the total magnetization, M, is conserved, it is meaningful to
study the spectrum for each fixed value of M. We prove that for J>= 3/2 the
lowest excited eigenvalues are separated by a gap from the rest of the
spectrum, uniformly in the length of the chain. In the thermodynamic limit,
this means that there are a positive number of excitations above the ground
state and below the essential spectrum
Finite-Connectivity Spin-Glass Phase Diagrams and Low Density Parity Check Codes
We obtain phase diagrams of regular and irregular finite connectivity
spin-glasses. Contact is firstly established between properties of the phase
diagram and the performances of low density parity check codes (LDPC) within
the Replica Symmetric (RS) ansatz. We then study the location of the dynamical
and critical transition of these systems within the one step Replica Symmetry
Breaking theory (RSB), extending similar calculations that have been performed
in the past for the Bethe spin-glass problem. We observe that, away from the
Nishimori line, in the low temperature region, the location of the dynamical
transition line does change within the RSB theory, in comparison with the (RS)
case. For LDPC decoding over the binary erasure channel we find, at zero
temperature and rate R=1/4 an RS critical transition point located at p_c =
0.67 while the critical RSB transition point is located at p_c = 0.7450, to be
compared with the corresponding Shannon bound 1-R. For the binary symmetric
channel (BSC) we show that the low temperature reentrant behavior of the
dynamical transition line, observed within the RS ansatz, changes within the
RSB theory; the location of the dynamical transition point occurring at higher
values of the channel noise. Possible practical implications to improve the
performances of the state-of-the-art error correcting codes are discussed.Comment: 21 pages, 15 figure
Information Theory based on Non-additive Information Content
We generalize the Shannon's information theory in a nonadditive way by
focusing on the source coding theorem. The nonadditive information content we
adopted is consistent with the concept of the form invariance structure of the
nonextensive entropy. Some general properties of the nonadditive information
entropy are studied, in addition, the relation between the nonadditivity
and the codeword length is pointed out.Comment: 9 pages, no figures, RevTex, accepted for publication in Phys. Rev.
E(an error in proof of theorem 1 was corrected, typos corrected
Structure and superconducting properties of ((Ln(1-x)Ln*(x) 1/2 (Ba(1-y)Sr(y) 1/3 Ce 1/6) 8Cu6O(z)
A variety of new oxide superconductors were prepared. The crystallographic structures of the oxides were all tetragonal and of the (Ln(+), Ce)4(Ln(+),Ba)4Cu6Oz (Ln(+) = Nd, Sm or Eu) type which had been previously discovered by Akimitsu et al. As the Sr content, y, increased when Ln = Ln(excited state) = Nd, the oxygen content, z, monotonically increased and the superconducting transition temperature, T(sub c), varied exhibiting a maximum. When z was controlled directly by means of high oxygen pressure sintering techniques, T(sub c) was changed accordingly. T(sub c's) of samples with different combinations of Ln and Ln(excited state) and different values of x and y were found to depend on the magnitude of the bond valence sum for a Cu atom located in the bottom plane of the Cu-O5 pyramid. Transport and magnetization measurements were carried out to investigate the magnetic field dependence of superconducting properties and to determine the phenomenological parameters. The Hall coefficients were positive below room temperature and varied yielding a maximum with respect to temperature
Thermodynamic time asymmetry in nonequilibrium fluctuations
We here present the complete analysis of experiments on driven Brownian
motion and electric noise in a circuit, showing that thermodynamic entropy
production can be related to the breaking of time-reversal symmetry in the
statistical description of these nonequilibrium systems. The symmetry breaking
can be expressed in terms of dynamical entropies per unit time, one for the
forward process and the other for the time-reversed process. These entropies
per unit time characterize dynamical randomness, i.e., temporal disorder, in
time series of the nonequilibrium fluctuations. Their difference gives the
well-known thermodynamic entropy production, which thus finds its origin in the
time asymmetry of dynamical randomness, alias temporal disorder, in systems
driven out of equilibrium.Comment: to be published in : Journal of Statistical Mechanics: theory and
experimen
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