1,457 research outputs found
Trotter-Kato product formulae in Dixmier ideal
It is shown that for a certain class of the Kato functions the Trotter-Kato
product formulae converge in Dixmier ideal C 1, in topology, which is
defined by the 1,-norm. Moreover, the rate of convergence in
this topology inherits the error-bound estimate for the corresponding
operator-norm convergence. 1 since [24], [14]. Note that a subtle point of this
program is the question about the rate of convergence in the corresponding
topology. Since the limit of the Trotter-Kato product formula is a strongly
continuous semigroup, for the von Neumann-Schatten ideals this topology is the
trace-norm 1 on the trace-class ideal C 1 (H). In this case the limit
is a Gibbs semigroup [25]. For self-adjoint Gibbs semigroups the rate of
convergence was estimated for the first time in [7] and [9]. The authors
considered the case of the Gibbs-Schr{\"o}dinger semigroups. They scrutinised
in these papers a dependence of the rate of convergence for the (exponential)
Trotter formula on the smoothness of the potential in the Schr{\"o}dinger
generator. The first abstract result in this direction was due to [19]. In this
paper a general scheme of lifting the operator-norm rate convergence for the
Trotter-Kato product formulae was proposed and advocated for estimation the
rate of the trace-nor
Remarks on the operator-norm convergence of the Trotter product formula
We revise the operator-norm convergence of the Trotter product formula for a
pair {A,B} of generators of semigroups on a Banach space. Operator-norm
convergence holds true if the dominating operator A generates a holomorphic
contraction semigroup and B is a A-infinitesimally small generator of a
contraction semigroup, in particular, if B is a bounded operator. Inspired by
studies of evolution semigroups it is shown in the present paper that the
operator-norm convergence generally fails even for bounded operators B if A is
not a holomorphic generator. Moreover, it is shown that operator norm
convergence of the Trotter product formula can be arbitrary slow.Comment: 12 page
The effect of time-dependent coupling on non-equilibrium steady states
Consider (for simplicity) two one-dimensional semi-infinite leads coupled to
a quantum well via time dependent point interactions. In the remote past the
system is decoupled, and each of its components is at thermal equilibrium. In
the remote future the system is fully coupled. We define and compute the non
equilibrium steady state (NESS) generated by this evolution. We show that when
restricted to the subspace of absolute continuity of the fully coupled system,
the state does not depend at all on the switching. Moreover, we show that the
stationary charge current has the same invariant property, and derive the
Landau-Lifschitz and Landauer-Buttiker formulas.Comment: 30 pages, submitte
Non-equilibrium current via geometric scatterers
We investigate non-equilibrium particle transport in the system consisting of
a geometric scatterer and two leads coupled to heat baths with different
chemical potentials. We derive expression for the corresponding current the
carriers of which are fermions and analyze numerically its dependence of the
model parameters in examples, where the scatterer has a rectangular or
triangular shape.Comment: 18 pages, 8 figure
VLBI2010 - The TWIN radio telescope project at Wettzell, Germany
The Twin Telescope Wettzell (TTW) Project is funded to be exec
uted during the period of 2008-2011. The design of the TTW was based on the VLBI2010 vision of the corresponding IVS Working Group. In the first two project years the design passed the simulations with respect to its specifications and was approved for production. At the Geodetic Observatory Wettzell a thorough soil analysis was made in order to define the sites for the towers of the new radio telescopes. Meanwhile the construction work has begun and acceptance tests of several telescope parts, e.g. azimuth bearings, took place. The full assembly of the radio telescopes is scheduled for the next two years. In parallel to the construction work at the Wettzell site, the design work for the different feed options progressed
Linear non-autonomous Cauchy problems and evolution semigroups
The paper is devoted to the problem of existence of propagators for an
abstract linear non-autonomous evolution Cauchy problem of hyperbolic type in
separable Banach spaces. The problem is solved using the so-called evolution
semigroup approach which reduces the existence problem for propagators to a
perturbation problem of semigroup generators. The results are specified to
abstract linear non-autonomous evolution equations in Hilbert spaces where the
assumption is made that the domains of the quadratic forms associated with the
generators are independent of time. Finally, these results are applied to
time-dependent Schr\"odinger operators with moving point interactions in 1D
Convergence rate estimates for Trotter product approximations of solution operators for non-autonomous Cauchy problems
In the present paper we advocate the Howland-Evans approach to solution of the abstract non-autonomous Cauchy problem (non-ACP) in a separable Banach space X. The main idea is to reformulate this problem as an autonomous Cauchy problem (ACP) in a new Banach space Lp(J,X), consisting of X-valued functions on the time-interval J. The fundamental observation is a one-to-one correspondence between solution operators (propagators) for a non-ACP and the corresponding evolution semigroups for ACP in Lp(J,X). We show that the latter also allows to apply a full power of the operator-theoretical methods to scrutinise the non-ACP including the proof of the Trotter product approximation formulae with operator-norm estimate of the rate of convergence. The paper extends and improves some recent results in this direction in particular for Hilbert spaces
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