1,741 research outputs found
Wigner functions of thermo number state, photon subtracted and added thermo vacuum state at finite temperature
Based on Takahashi-Umezawa thermo field dynamics and the order-invariance of
Weyl ordered operators under similar transformations, we present a new approach
to deriving the exact Wigner functions of thermo number state, photon
subtracted and added thermo vacuum state. We find that these Wigner functions
are related to the Gaussian-Laguerre type functions of temperature, whose
statistical properties are then analysed.Comment: 10 pages and 2 figure
String Entanglement and D-branes as Pure States
We study the entanglement of closed strings degrees of freedom in order to
investigate the microscopic structure and statistics of objects as D-branes. By
considering the macroscopic pure state (MPS) limit, whenever the entanglement
entropy goes to zero (in such a way that the macroscopic properties of the
state are preserved), we show that boundary states may be recovered in this
limit and, furthermore, the description through closed string (perturbative)
degrees of freedom collapses. We also show how the thermal properties of branes
and closed strings could be described by this model, and it requires that
dissipative effects be taken into account. Extensions of the MPS analysis to
more general systems at finite temperature are finally emphasized.Comment: 14 pages. Minor improvements. Published in Phys. Rev.
No-cloning theorem in thermofield dynamics
We discuss the relation between the no-cloning theorem from quantum
information and the doubling procedure used in the formalism of thermofield
dynamics (TFD). We also discuss how to apply the no-cloning theorem in the
context of thermofield states defined in TFD. Consequences associated to mixed
states, von Neumann entropy and thermofield vacuum are also addressed.Comment: 16 pages, 3 figure
Topological Discrete Algebra, Ground State Degeneracy, and Quark Confinement in QCD
Based on the permutation group formalism, we present a discrete symmetry
algebra in QCD. The discrete algebra is hidden symmetry in QCD, which is
manifest only on a space-manifold with non-trivial topology. Quark confinement
in the presence of the dynamical quarks is discussed in terms of the discrete
symmetry algebra. It is shown that the quark deconfinement phase has the ground
state degeneracy depending on the topology of the space, which gives a
gauge-invariant distinction between the confinement and deconfinement phases.
We also point out that new quantum numbers relating to the fractional quantum
Hall effect exist in the deconfinement phase.Comment: 11 pages, 1 figur
Superconductivity in CVD Diamond Thin Film Well-Above Liquid Helium Temperature
Diamond has always been adored as a jewel. Even more fascinating is its
outstanding physical properties; it is the hardest material known in the world
with the highest thermal conductivity. Meanwhile, when we turn to its
electrical properties, diamond is a rather featureless electrical insulator.
However, with boron doping, it becomes a p-type semiconductor, with boron
acting as a charge acceptor. Therefore the recent news of superconductivity in
heavily boron-doped diamond synthesized by high pressure sintering was received
with considerable surprise. Opening up new possibilities for diamond-based
electrical devices, a systematic investigation of these phenomena clearly needs
to be achieved. Here we show unambiguous evidence of superconductivity in a
diamond thin film deposited by a chemical vapor deposition (CVD) method.
Furthermore the onset of the superconducting transition is found to be 7.4K,
which is higher than the reported value in ref(7) and well above helium liquid
temperature. This finding establishes the superconductivity to be a universal
property of boron-doped diamond, demonstrating that device application is
indeed a feasible challenge.Comment: 6 pages, 3 figure
Spectral properties of a spin-incoherent Luttinger Liquid
We present time-dependent density matrix renormalization group (DMRG) results
for strongly interacting one dimensional fermionic systems at finite
temperature. When interactions are strong the characteristic spin energy can be
greatly suppressed relative to the characteristic charge energy, allowing for
the possibility of spin-incoherent Luttinger liquid physics when the
temperature is high compared to the spin energy, but small compared to the
charge energy. Using DMRG we compute the spectral properties of the model
at arbitrary temperatures with respect to both spin and charge energies. We
study the full crossover from the Luttinger liquid regime to the
spin-incoherent regime,focusing on small , where the signatures of
spin-incoherent behavior are more manifest. Our method allows us to access the
analytically intractable regime where temperature is of the order of the spin
energy, . Our results should be helpful in the interpretation of
experiments that may be in the crossover regime, , and apply to
one-dimensional cold atomic gases where finite-temperature effects are
appreciable. The technique may also be used to guide the development of
analytical approximations for the crossover regime.Comment: 7 pages, 5 figure
TFD Approach to Bosonic Strings and -branes
In this work we explain the construction of the thermal vacuum for the
bosonic string, as well that of the thermal boundary state interpreted as a
-brane at finite temperature. In both case we calculate the respective
entropy using the entropy operator of the Thermo Field Dynamics Theory. We show
that the contribution of the thermal string entropy is explicitly present in
the -brane entropy. Furthermore, we show that the Thermo Field approach
is suitable to introduce temperature in boundary states.Comment: 6 pages, revtex, typos are corrected. Prepared for the Second
Londrina Winter School-Mathematical Methods in Physics, August 25-30, 2002,
Londrina-Pr, Brazil. To appear in a special issue of IJMP
Noncommutative Thermofield Dynamics
The real-time operator formalism for thermal quantum field theories,
thermofield dynamics, is formulated in terms of a path-integral approach in
non-commutative spaces. As an application, the two-point function for a thermal
non-commutative theory is derived at the one-loop level. The
effect of temperature and the non-commutative parameter, competing with one
another, is analyzed.Comment: 13 pages; to be published in IJMP-A
Two-Dimensional Order and Disorder Thermofields
The main objective of this paper was to obtain the two-dimensional order and
disorder thermal operators using the Thermofield Bosonization formalism. We
show that the general property of the two-dimensional world according with the
bosonized Fermi field at zero temperature can be constructed as a product of an
order and a disorder variables which satisfy a dual field algebra holds at
finite temperature. The general correlation functions of the order and disorder
thermofields are obtained.Comment: 4 page
A New Kind of Uniformly Accelerated Reference Frames
A new kind of uniformly accelerated reference frames with a line-element
different from the M{\o}ller and Rindler ones is presented, in which every
observer at consts. has the same constant acceleration. The laws of
mechanics are checked in the new kind of frames. Its thermal property is
studied. The comparison with the M{\o}ller and Rindler uniform accelerated
reference frames is also made.Comment: 10 pages, 2 figures. to appear in Int. J. Mod. Phys.
- …