536 research outputs found
On multi-transitivity with respect to a vector
A topological dynamical system is said to be multi-transitive if for
every the system is transitive. We introduce the concept of multi-transitivity with
respect to a vector and show that multi-transitivity can be characterized by
the hitting time sets of open sets, answering a question proposed by Kwietniak
and Oprocha [On weak mixing, minimality and weak disjointness of all iterates,
Erg. Th. Dynam. Syst., 32 (2012), 1661--1672]. We also show that
multi-transitive systems are Li-Yorke chaotic.Comment: 11 page
Quantum phonon transport of molecular junctions amide-linked with carbon nanotubes: a first-principle study
Quantum phonon transport through benzene and alkane chains amide-linked with
single wall carbon nanotubes (SWCNTs) is studied within the level of density
functional theory. The force constant matrices are obtained from standard
quantum chemistry software. The phonon transmission and thermal conductance are
from the nonequilibrium Green's function and the mode-matching method. We find
that the ballistic thermal conductance is not sensitive to the compression or
stretching of the molecular junction. The terminating groups of the SWCNTs at
the cutting edges only influence the thermal conductance quantitatively. The
conductance of the benzene and alkane chains shows large difference. Analysis
of the transmission spectrum shows that (i) the low temperature thermal
conductance is mainly contributed by the SWCNT transverse acoustic modes, (ii)
the degenerate phonon modes show different transmission probability due to the
presence of molecular junction, (iii) the SWCNT twisting mode can hardly be
transmitted by the alkane chain. As a result, the ballistic thermal conductance
of alkane chains is larger than that of benzene chains below 38 K, while it is
smaller at higher temperature.Comment: 5 pages, 5 figure
Searching for Heavier Higgs Boson via Di-Higgs Production at LHC Run-2
The LHC discovery of a light Higgs particle (125GeV) opens up new
prospect for searching heavier Higgs boson(s) at the LHC Run-2, which will
unambiguously point to new physics beyond the standard model (SM). We study the
detection of a heavier neutral Higgs boson via di-Higgs production
channel at the LHC (14TeV), . This
directly probes the cubic Higgs interaction, which exists in most
extensions of the SM Higgs sector. For the decay products of final states
, we include both pure leptonic mode and semi-leptonic mode .
We analyze signals and backgrounds by performing fast detector simulation for
the full processes and , over the mass range
GeV. For generic two-Higgs-doublet models (2HDM), we present the
discovery reach of the heavier Higgs boson at the LHC Run-2, and compare it
with the current Higgs global fit of the 2HDM parameter space.Comment: Phys.Lett.B Final Version. 16pp (9 Figs + 4 Tables). Only minor
refinements, references adde
Crystallographic Distinction between “Contact” and “Separated” Ion Pairs: Structural Effects on Electronic/ESR Spectra of Alkali-Metal Nitrobenzenides
The classic nitrobenzene anion-radical (NB-• or nitrobenzenide) is isolated for the first time as pure crystalline alkali-metal salts. The deliberate use of the supporting ligands 18-crown-6 and [2.2.2]cryptand allows the selective formation of contact ion pairs designated as (crown)M+NB-•, where M+ = K+, Rb+, and Cs+, as well as the separated ion pair K(cryptand)+NB-•both series of which are structurally characterized by precise low-temperature X-ray crystallography, ESR analysis, and UV−vis spectroscopy. The unusually delocalized structure of NB-• in the separated ion pair follows from the drastically shortened N−C bond and marked quinonoidal distortion of the benzenoid ring to signify complete (95%) electronic conjugation with the nitro substituent. On the other hand, the formation of contact ion pairs results in the substantial decrease of electronic conjugation in inverse order with cation size (K+ \u3e Rb+) owing to increased localization of negative charge from partial (NO2) bonding to the alkali-metal cation. Such a loss in electronic conjugation (or reverse charge transfer) may be counterintuitive, but it is in agreement with the distribution of odd-electron spin electron density from the ESR data and with the hypsochromic shift of the characteristic absorption band in the electronic spectra. Most importantly, this crystallographic study underscores the importance of ion-pair structure on the intrinsic property (and thus reactivity) of the component ions - as focused here on the nitrobenzenide anion
Current-induced forces and hot-spots in biased nano-junctions
We investigate theoretically the interplay of current-induced forces (CIF),
Joule heating, and heat transport inside a current-carrying nano-conductor. We
find that the CIF, due to the electron-phonon coherence, can control the
spatial heat dissipation in the conductor. This yields a significant asymmetric
concentration of excess heating (hot-spot) even for a symmetric conductor. When
coupled to the electrode phonons, CIF drive different phonon heat flux into the
two electrodes. First-principles calculations on realistic biased
nano-junctions illustrate the importance of the effect.Comment: Phys. Rev. Lett. accepted versio
Coupled electron and phonon transport in one-dimensional atomic junctions
Employing the nonequilibrium Green's function method, we develop a fully
quantum mechanical model to study the coupled electron-phonon transport in
one-dimensional atomic junctions in the presence of a weak electron-phonon
interaction. This model enables us to study the electronic and phononic
transport on an equal footing. We derive the electrical and energy currents of
the coupled electron-phonon system and the energy exchange between them. As an
application, we study the heat dissipation in current carrying atomic junctions
within the self-consistent Born approximation, which guarantees energy current
conservation. We find that the inclusion of phonon transport is important in
determining the heat dissipation and temperature change of the atomic
junctions.Comment: 10 pages, 7 figure
- …