1,139 research outputs found
T violation and the unidirectionality of time
An increasing number of experiments at the Belle, BNL, CERN, DA{\Phi}NE and
SLAC accelerators are confirming the violation of time reversal invariance (T).
The violation signifies a fundamental asymmetry between the past and future and
calls for a major shift in the way we think about time. Here we show that
processes which violate T symmetry induce destructive interference between
different paths that the universe can take through time. The interference
eliminates all paths except for two that represent continuously forwards and
continuously backwards time evolution. Evidence from the accelerator
experiments indicates which path the universe is effectively following. This
work may provide fresh insight into the long-standing problem of modeling the
dynamics of T violation processes. It suggests that T violation has previously
unknown, large-scale physical effects and that these effects underlie the
origin of the unidirectionality of time. It may have implications for the
Wheeler-DeWitt equation of canonical quantum gravity. Finally it provides a
view of the quantum nature of time itself.Comment: 24 pages, 5 figures. Final version accepted for publishing in
Foundations of Physics. The final publication is available at
http://www.springerlink.com/content/y3h4174jw2w78322
Three-Loop Chromomagnetic Interaction in HQET
We compute the three-loop QCD corrections to the quark chromomagnetic moment
and thus obtain the matching coefficient and the anomalous dimension of the
chromomagnetic interaction in HQET. As a byproduct we obtain the three-loop
corrections to the quark anomalous magnetic moment.Comment: 22 page
Quantum Dynamics in Non-equilibrium Strongly Correlated Environments
We consider a quantum point contact between two Luttinger liquids coupled to
a mechanical system (oscillator). For non-vanishing bias, we find an effective
oscillator temperature that depends on the Luttinger parameter. A generalized
fluctuation-dissipation relation connects the decoherence and dissipation of
the oscillator to the current-voltage characteristics of the device. Via a
spectral representation, this result is generalized to arbitrary leads in a
weak tunneling regime.Comment: 4 pages, 1 figur
A review of the Dividend Discount Model: from deterministic to stochastic models
This chapter presents a review of the dividend discount models starting from
the basic models (Williams 1938, Gordon and Shapiro 1956) to more recent and
complex models (Ghezzi and Piccardi 2003, Barbu et al. 2017, D'Amico and De
Blasis 2018) with a focus on the modelling of the dividend process rather than
the discounting factor, that is assumed constant in most of the models. The
Chapter starts with an introduction of the basic valuation model with some
general aspects to consider when performing the computation. Then, Section 1.3
presents the Gordon growth model (Gordon 1962) with some of its extensions
(Malkiel 1963, Fuller and Hsia 1984, Molodovsky et al. 1965, Brooks and Helms
1990, Barsky and De Long 1993), and reports some empirical evidence. Extended
reviews of the Gordon stock valuation model and its extensions can be found in
Kamstra (2003) and Damodaran (2012). In Section 1.4, the focus is directed to
more recent advancements which make us of the Markov chain to model the
dividend process (Hurley and Johnson 1994, Yao 1997, Hurley and Johnson 1998,
Ghezzi and Piccardi 2003, Barbu et al. 2017, D'Amico and De Blasis 2018). The
advantage of these models is the possibility to obtain a different valuation
that depends on the state of the dividend series, allowing the model to be
closer to reality. In addition, these models permit to obtain a measure of the
risk of the single stock or a portfolio of stocks
Au+Au Reactions at the AGS: Experiments E866 and E917
Particle production and correlation functions from Au+Au reactions have been
measured as a function of both beam energy (2-10.7AGeV) and impact parameter.
These results are used to probe the dynamics of heavy-ion reactions, confront
hadronic models over a wide range of conditions and to search for the onset of
new phenomena.Comment: 12 pages, 14 figures, Talk presented at Quark Matter '9
Form Factors in the radiative pion decay
We perform an analysis of the form factors that rule the structure-dependent
amplitude in the radiative pion decay. The resonance contributions to pion -> e
nu_e gamma decays are computed through the proper construction of the vector
and axial-vector form factors by setting the QCD driven asymptotic properties
of the three-point Green functions VVP and VAP, and by demanding the smoothing
of the form factors at high transfer of momentum. A comparison between
theoretical and experimental determinations of the form factors is also carried
out. We also consider and evaluate the role played by a non-standard tensor
form factor. We conclude that, at present and due to the hadronic incertitudes,
the search for New Physics in this process is not feasible.Comment: 14 pages, no figures. Typos corrected. Accepted for publication in
The European Physical Journal
Tomonaga-Luttinger parameters for quantum wires
The low-energy properties of a homogeneous one-dimensional electron system
are completely specified by two Tomonaga-Luttinger parameters and
. In this paper we discuss microscopic estimates of the values of
these parameters in semiconductor quantum wires that exploit their relationship
to thermodynamic properties. Motivated by the recognized similarity between
correlations in the ground state of a one-dimensional electron liquid and
correlations in a Wigner crystal, we evaluate these thermodynamic quantities in
a self-consistent Hartree-Fock approximation. According to our calculations,
the Hartree-Fock approximation ground state is a Wigner crystal at all electron
densities and has antiferromagnetic order that gradually evolves from
spin-density-wave to localized in character as the density is lowered. Our
results for are in good agreement with weak-coupling perturbative
estimates at high densities, but deviate strongly at low
densities, especially when the electron-electron interaction is screened at
long distances. vanishes at small carrier density
whereas we conjecture that when , implying that
should pass through a minimum at an intermediate density.
Observation of such a non-monotonic dependence on particle density would allow
to measure the range of the microscopic interaction. In the spin sector we find
that the spin velocity decreases with increasing interaction strength or
decreasing . Strong correlation effects make it difficult to obtain fully
consistent estimates of from Hartree-Fock calculations. We
conjecture that v_{\sigma}/\vf\propto n/V_0 in the limit where
is the interaction strength.Comment: RevTeX, 23 pages, 8 figures include
The Dipion Mass Spectrum In e+e- Annihilation and tau Decay: A Dynamical (rho0, omega, phi) Mixing Approach
We readdress the problem of finding a simultaneous description of the pion
form factor data in e+e- annihilations and in tau decays. For this purpose, we
work in the framework of the Hidden Local Symmetry (HLS) Lagrangian and modify
the vector meson mass term by including the pion and kaon loop contributions.
This leads us to define the physical rho, omega and phi fields as linear
combinations of their ideal partners, with coefficients being meromorphic
functions of s, the square of the 4--momentum flowing into the vector meson
lines. This allows us to define a dynamical, i.e. s-dependent, vector meson
mixing scheme. The model is overconstrained by extending the framework in order
to include the description of all meson radiative (V P gamma and P gamma gamma
couplings) and leptonic (Ve+e- couplings) decays and also the isospin breaking
(omega/ phi --> pi+ pi-) decay modes. The model provides a simultaneous,
consistent and good description of the e+e- and tau dipion spectra. The
expression for pion form factor in the latter case is derived from those in the
former case by switching off the isospin breaking effects specific to e+e- and
switching on those for tau decays. Besides, the model also provides a good
account of all decay modes of the form V P gamma, Pgamma gamma as well as the
isospin breaking decay modes. It leads us to propose new reference values for
the rho^0 --> e+ e- and omega --> pi+ pi- partial widths which are part of our
description of the pion form factor. Other topics (phi --> K anti K, the rho
meson mass and width parameters) are briefly discussed. Therefore, we confirm
the 3.3 sigma discrepancy between the theoretical estimate of a_mu based on
e+e- and its direct BNL measurement.Comment: 71 pages, 8 figures. Accepted by EPJ C. Version 3: correct minor
typos, minor changes spread out into the text. Extension of Sections 12.2 and
12.3.5 and introduction of the new Appendix
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