8,363 research outputs found
Heat Conduction in One-Dimensional chain of Hard Discs with Substrate Potential
Heat conduction of one-dimensional chain of equivalent rigid particles in the
field of external on-site potential is considered. Zero diameters of the
particles correspond to exactly integrable case with divergent heat conduction
coefficient. By means of simple analytical model it is demonstrated that for
any nonzero particle size the integrability is violated and the heat conduction
coefficient converges. The result of the analytical computation is verified by
means of numerical simulation in a plausible diapason of parameters and good
agreement is observedComment: 14 pages, 7 figure
Elliptic operators in odd subspaces
An elliptic theory is constructed for operators acting in subspaces defined
via odd pseudodifferential projections. Subspaces of this type arise as
Calderon subspaces for first order elliptic differential operators on manifolds
with boundary, or as spectral subspaces for self-adjoint elliptic differential
operators of odd order. Index formulas are obtained for operators in odd
subspaces on closed manifolds and for general boundary value problems. We prove
that the eta-invariant of operators of odd order on even-dimesional manifolds
is a dyadic rational number.Comment: 27 page
Elliptic operators in even subspaces
In the paper we consider the theory of elliptic operators acting in subspaces
defined by pseudodifferential projections. This theory on closed manifolds is
connected with the theory of boundary value problems for operators violating
Atiyah-Bott condition. We prove an index formula for elliptic operators in
subspaces defined by even projections on odd-dimensional manifolds and for
boundary value problems, generalizing the classical result of Atiyah-Bott.
Besides a topological contribution of Atiyah-Singer type, the index formulas
contain an invariant of subspaces defined by even projections. This homotopy
invariant can be expressed in terms of the eta-invariant. The results also shed
new light on P.Gilkey's work on eta-invariants of even-order operators.Comment: 39 pages, 2 figure
Vibrational Tamm states at the edges of graphene nanoribbons
We study vibrational states localized at the edges of graphene nanoribbons.
Such surface oscillations can be considered as a phonon analog of Tamm states
well known in the electronic theory. We consider both armchair and zigzag
graphene stripes and demonstrate that surface modes correspond to phonons
localized at the edges of the graphene nanoribbon, and they can be classified
as in-plane and out-of-plane modes. In addition, in armchair nanoribbons
anharmonic edge modes can experience longitudinal localization in the form of
self-localized nonlinear modes, or surface breather solitons.Comment: 10 pages, 10 figure
Dielectronic recombination data for astrophysical applications: Plasma rate-coefficients for Fe^q+ (q=7-10, 13-22) and Ni^25+ ions from storage-ring experiments
This review summarizes the present status of an ongoing experimental effort
to provide reliable rate coefficients for dielectronic recombination of highly
charged iron ions for the modeling of astrophysical and other plasmas. The
experimental work has been carried out over more than a decade at the heavy-ion
storage-ring TSR of the Max-Planck-Institute for Nuclear Physics in Heidelberg,
Germany. The experimental and data reduction procedures are outlined. The role
of previously disregarded processes such as fine-structure core excitations and
trielectronic recombination is highlighted. Plasma rate coefficients for
dielectronic recombination of Fe^q+ ions (q=7-10, 13-22) and Ni^25+ are
presented graphically and in a simple parameterized form allowing for easy use
in plasma modeling codes. It is concluded that storage-ring experiments are
presently the only source for reliable low-temperature dielectronic
recombination rate-coefficients of complex ions.Comment: submitted for publication in the International Review of Atomic and
Molecular Physics, 8 figures, 3 tables, 68 reference
Parity effect in Al and Nb single electron transistors in a tunable environment
Two different types of Cooper pair transistors, with Al and Nb islands, have
been investigated in a tunable electromagnetic environment. The device with an
Al island demonstrates gate charge modulation with 2e-periodicity in a wide
range of environmental impedances at bath temperatures below 340 mK. Contrary
to the results of the Al sample, we were not able to detect 2e-periodicity
under any conditions on similar samples with Nb island. We attribute this to
the material properties of Nb.Comment: 3 pages, 3 figure
Manipulation and Generation of Supercurrent in Out-of-Equilibrium Josephson Tunnel Nanojunctions
We demonstrate experimentally manipulation of supercurrent in Al-AlO_x-Ti
Josephson tunnel junctions by injecting quasiparticles in a Ti island from two
additional tunnel-coupled Al superconducting reservoirs. Both supercurrent
enhancement and quenching with respect to equilibrium are achieved. We
demonstrate cooling of the Ti line by quasiparticle injection from the normal
state deep into the superconducting phase. A model based on heat transport and
non-monotonic current-voltage characteristic of a Josephson junction
satisfactorily accounts for our findings.Comment: 4 pages, 4 colour figures, published versio
Learning at the Interstices; Locating Practical Philosophies for Understanding Physical/virtual Inter-spaces
Virtual worlds are relatively recent developments, and so it is tempting to believe that they need to be understood through newly developed theories and philosophies. However, humans have long thought about the nature of reality and what it means to be “real.” This paper examines the three persistent philosophical concepts of Metaxis, Liminality and Space that have evolved across more than 2000 years of meditation, contemplation and reflection. Our particular focus here is on the nature of the interface between the virtual and the physical: at the interstices, and how the nature of transactions and transitions across those interfaces may impact upon learning. This may, at first, appear to be an esoteric pursuit, but we ground our arguments in primary and secondary data from research studies in higher education
On the nonlinear dynamics of topological solitons in DNA
Dynamics of topological solitons describing open states in the DNA double
helix are studied in the frameworks of the model which takes into account
asymmetry of the helix. It is shown that three types of topological solitons
can occur in the DNA double chain. Interaction between the solitons, their
interactions with the chain inhomogeneities and stability of the solitons with
respect to thermal oscillations are investigated.Comment: 16 pages, 16 figure
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