446 research outputs found
On multiplicative functions which are small on average
Let be a completely multiplicative function that assumes values inside
the unit disc. We show that if \sum_{n2, for
some , then either is small on average or pretends to be
for some .Comment: 51 pages. Slightly strengthened Theorem 1.2 and simplified its
statement. Removed Remark 1.3. Other minor changes and corrections. To appear
in Geom. Funct. Ana
Rovibronic spectra of molecules dressed by light fields
The theory of rovibronic spectroscopy of light-dressed molecules is presented
within the framework of quantum mechanically treated molecules interacting with
classical light fields. Numerical applications are demonstrated for the
homonuclear diatomic molecule Na, for which the general formulae can be
simplified considerably and the physical processes leading to the light-dressed
spectra can be understood straightforwardly. The physical origin of different
peaks in the light-dressed spectrum of Na is given and the light-dressed
spectrum is investigated in terms of its dependence on the dressing field's
intensity and wavelength, the turn-on time of the dressing field, and the
temperature. The important implications of light-dressed spectroscopy on
deriving field-free spectroscopic quantities are also discussed
On the preservation of coherence in the electronic wavepacket of a neutral and rigid polyatomic molecule
We present various types of reduced models including five vibrational modes
and three electronic states for the pyrazine molecule in order to investigate
the lifetime of electronic coherence in a rigid and neutral system. Using an
ultrafast optical pumping in the ground state (1 1 A g ), we prepare a coherent
superposition of two bright excited states, 1 1 B 2u and 1 1 B 1u , and reveal
the effect of the nuclear motion on the preservation of the electronic
coherence induced by the laser pulse. More specifically, two aspects are
considered: the anharmonicity of the potential energy surfaces and the
dependence of the transition dipole moments (TDMs) with respect to the nuclear
coordinates. To this end, we define an ideal model by making three
approximations: (i) only the five totally symmetric modes move, (ii) which
correspond to uncoupled harmonic oscillators, and (iii) the TDMs from the
ground electronic state to the two bright states are constant (Franck-Condon
approximation). We then lift the second and third approximations by
considering, first, the effect of anharmonicity, second, the effect of
coordinate-dependence of the TDMs (first-order Herzberg- Teller contribution),
third, both. Our detailed numerical study with quantum dynamics confirms
long-term revivals of the electronic coherence even for the most realistic
model
Critical current of a Josephson junction containing a conical magnet
We calculate the critical current of a
superconductor/ferromagnetic/superconductor (S/FM/S) Josephson junction in
which the FM layer has a conical magnetic structure composed of an in-plane
rotating antiferromagnetic phase and an out-of-plane ferromagnetic component.
In view of the realistic electronic properties and magnetic structures that can
be formed when conical magnets such as Ho are grown with a polycrystalline
structure in thin-film form by methods such as direct current sputtering and
evaporation, we have modeled this situation in the dirty limit with a large
magnetic coherence length (). This means that the electron mean free
path is much smaller than the normalized spiral length which in
turn is much smaller than (with as the length a complete
spiral makes along the growth direction of the FM). In this physically
reasonable limit we have employed the linearized Usadel equations: we find that
the triplet correlations are short ranged and manifested in the critical
current as a rapid oscillation on the scale of . These rapid
oscillations in the critical current are superimposed on a slower oscillation
which is related to the singlet correlations. Both oscillations decay on the
scale of . We derive an analytical solution and also describe a
computational method for obtaining the critical current as a function of the
conical magnetic layer thickness.Comment: Extended version of the published paper. Additional information about
the computational method is included in the appendi
New approach for estimation of incident energy on high voltage level
Abstract
The purpose of this paper is to show a new calculation model, which is able to calculate the incident energy in any places near an electric arc in case of high voltage, without neglecting of length and position of the electric arc. This method is developed especially for the electric transmission network above 35 kV and several meters of gap distances. It would be used to estimate the thermal load of a power line worker close an initiated electric arc during live-line maintenance by bare-hand and hot stick method as well
- …