1,503 research outputs found
Asymmetry of the excess finite-frequency noise
We consider finite frequency noise in a mesoscopic system with arbitrary
interactions, connected to many terminals kept at finite electrochemical
potentials. We show that the excess noise, obtained by subtracting the noise at
zero voltage from that at finite voltage, can be asymmetric with respect to
positive/negative frequencies if the system is non-linear. This explains a
recent experimental observation in Josephson junctions as well as strong
asymmetry obtained in typical non-linear and strongly correlated systems
described by the Luttinger liquid (LL): edge states in the fractional quantum
Hall effect, quantum wires and carbon nanotubes. Another important problem
where the LL model applies is that of a coherent conductor embedded in an ohmic
environment.Comment: 4 pages, 1 figur
Poor qubits make for rich physics: noise-induced quantum Zeno effects and noise-induced Berry phases
We briefly review three ways that environmental noise can slow-down (or
speed-up) quantum transitions; (i) Lamb shifts, (ii) over-damping and (iii)
orthogonality catastrophe. We compare them with the quantum Zeno effect induced
by observing the system. These effects are relevant to poor qubits (those
strongly coupled to noise). We discuss Berry phases generated by the
orthogonality catastrophe, and argue that noise may make it easier to observe
Berry phases.Comment: 6 pages - Proceedings of International Conference on Noise and
Fluctuations (Pisa, 14-19 June 2009) - Improved with respect to version in
Conf. Pro
The pure model and future linear colliders: the Higgs sector
We summarise the phenomenology of the Higgs sector of the minimal
extension of the Standard Model at an Linear Collider. Within such a
scenario, we show that (in comparison with the Large Hadron Collider) several
novel production and decay channels involving the two physical Higgs states
could experimentally be accessed at such a machine. In particular, we present
the scope of the strahlung process for single and double Higgs production,
the only suitable mechanism for accessing an almost decoupled heavy scalar
state.Comment: This proceeding of the 2011 International Workshop on Future Linear
Colliders (LCWS11) is published through the SLAC Electronic Conference
Proceedings Archiv
Charged-Higgs production in the Two-Higgs-Doublet Model --- the \tau\nu channel
We update the allowed parameter space of the CP-violating 2HDM with Type II
Yukawa couplings, that survives the current experimental and theoretical
constraints on the model. For a representative set of allowed parameter points,
we study the production of charged Higgs bosons, both at the LHC at 14 TeV and
at a possible future hadronic collider at 30 TeV. Two classes of production
mechanisms are considered, "bosonic" (pp\to H^\pm W^\mp X) and "fermionic" (pp
\to H^+ \bar t (b) X). After commenting on our previous H^\pm\to W^\pm H_1
investigation, we focus on the tauonic decay mode, H^\pm \to \tau\nu,
performing a detailed signal-over-background analysis at the parton level. The
increased features provided when considering CP violation, i.e., the extension
of the parameter space and the mixing of the would-be CP-odd scalar boson, only
marginally increase the discovery prospects, which remain very challenging both
when increased luminosities and higher energies are considered.Comment: 26 pages, 13 figures. v2 Version published in JHE
Fluctuation relations without micro-reversibility for two-terminal conductors
In linear transport, the fluctuation-dissipation theorem relates equilibrium
current correlations to the linear conductance coefficient. Theory and
experiment have shown that in small electrical conductors the non-linear
I-V-characteristic of two-terminal conductor exhibits terms which are
asymmetric in magnetic field and thus micro-reversibility is manifestly broken.
We discuss a non-equilibrium fluctuation dissipation theorem which is not based
on micro-reversibility. It connects the antisymmetric nonlinear conductance
with the third cumulant of equilibrium current fluctuations and a noise term
that is proportional to temperature, magnetic field and voltage.Comment: 6 pages, 2 figures, corrected typo
Effect of potential fluctuations on shot noise suppression in mesoscopic cavities
We perform a numerical investigation of the effect of the disorder associated
with randomly located impurities on shot noise in mesoscopic cavities. We show
that such a disorder becomes dominant in determining the noise behavior when
the amplitude of the potential fluctuations is comparable to the value of the
Fermi energy and for a large enough density of impurities. In contrast to
existing conjectures, random potential fluctuations are shown not to contribute
to achieving the chaotic regime whose signature is a Fano factor of 1/4, but,
rather, to the diffusive behavior typical of disordered conductors. In
particular, the 1/4 suppression factor expected for a symmetric cavity can be
achieved only in high-quality material, with a very low density of impurities.
As the disorder strength is increased, a relatively rapid transition of the
suppression factor from 1/4 to values typical of diffusive or quasi-diffusive
transport is observed. Finally, on the basis of a comparison between a
hard-wall and a realistic model of the cavity, we conclude that the specific
details of the confinement potential have a minor influence on noise.Comment: 8 pages, 10 figures. This is the final version published in AIP
Advances. With respect to the previous arXiv version, there are some changes
in the text (mainly in the introduction and in the references); the numerical
results are unchange
RECONSTRUCTION OF A LOST CARBONATE FACTORY BASED ON ITS BIOGENIC DETRITUS (TERNATE-TRAVEDONA FORMATION AND GONFOLITE LOMBARDA GROUP - NORTHERN ITALY)
This work reconstructs a now completely eroded late Eocene to earliest Oligocene carbonate factory of Northern Italy, through the analysis of a carbonate deep-water-fan sequence (Ternate-Travedona Formation) and the limestone detritus dispersed into the late Oligocene clastic-wedge of the Gonfolite Lombarda Group. Textural characteristics and skeletal assemblages of the Gonfolite pebbles were studied and compared to those of the Ternate-Travedona Formation. The same skeletal assemblage and the same taxa were found in samples from both areas, suggesting their common origin. Whereas the Ternate-Travedona Formation skeletal grains were reworked during transport, the Gonfolite Lombarda Group pure-limestone pebbles are pristine fragments of the carbonate platform, that was uplifted and eroded from the late Eocene to the early Oligocene. Using both these sources of information it was possible to reconstruct the late Eocene environment and its facies distribution. The areas undergoing high hydrodynamic energy were dominated by free-living coralline-algal branches, rhodoliths and larger thick-tested benthic foraminifera. A coralline framework, associated with thin-tested benthic foraminifera and boxwork rhodoliths, was present in slightly deeper and sheltered environments. Episodic debris flows, mainly triggered by river floods, supplied the sub-marine fan of the Ternate-Travedona Formation. These events were able to down-cut through the narrow platform and rip off large fragments of the substrate. River runoff probably also supplied large quantities of organic matter, leading to local oxygen-depletion and preservation of organic matter. The combined stressful effects of bottom instability and riverine discharge probably excluded corals from the association. The integrated study of the Ternate-Travedona Formation, and of the limestone pebbles in the Gonfolite Group, have enabled the reconstruction of this otherwise lost Eocene carbonate factory
Innovative, green, floating radiosondes to track small-scale fluctuations along isopycnic surfaces in and around warm clouds
Clouds are an important source of uncertainty in climate modelling and weather prediction models. Warm clouds have a cloud top that doesn’t contain any ice forms and are found to be responsible for 31% of the world’s rainfall. Hence, innovative, green, ultralight radiosondes are being conceived within the context of the H2020 MSCA ITN ClOud-MicroPhysics-turbuLEnce-Telemetry (COMPLETE) network, which aims to characterise the cloud boundary, and develop the current understanding of cloud physics and related turbulent dynamics. The radiosondes conceived within this network will contribute to the current understanding of microphysical processes in clouds in a range of a few 100m
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