13,118 research outputs found
Conventional Calibration Versus EDF Calibration
In this paper we analyze the impact of using alternative parameter calibration methodologies for general equilibrium models in the context of a particular application. When studying implications of different parameterizations on long-run equilibria for Chile, we find that the impact of free trade agreements on macroeconomic variables of interest is contingent on the choice of methodological approach. Nevertheless, steady state welfare gains due to the treaties are robust to different parameterizations.
Relativistic Quark Model Calculation of the l1, l2 Coefficients of the Chiral Lagrangian
We briefly report on a relativistic quark model scheme to calculate the
O(P^4) pion-pion vertex in the planar approximation and in the chiral limit.
The calculation is reduced to the solution of simple integral equations
(Bethe-Salpeter like) by an effective use of chiral Ward Identities. Specific
model computations are provided.Comment: Proc. V Intnal. Conf. on Quark Confinement and the Hadron Spectrum,
Gargnano,Italy 200
Chiral symmetry breaking for fermions charged under large Lie groups
We reexamine the dynamical generation of mass for fermions charged under
various Lie groups with equal charge and mass at a high Grand Unification
scale, extending the Renormalization Group Equations in the perturbative regime
to two-loops and matching to the Dyson-Schwinger Equations in the strong
coupling regime.Comment: 8 pages, 12 plot
Soft interactions in jet quenching
We study the collisional aspects of jet quenching in a high energy nuclear
collision, especially in the final state pion gas. The jet has a large energy,
and acquires momentum transverse to its axis more effectively by multiple soft
collisions than by few hard scatterings (as known from analogous systems such
as J/\psi production at Hera). Such regime of large E and small momentum
transfer corresponds to Regge kinematics and is characteristically dominated by
the pomeron. From this insight we estimate the jet quenching parameter in the
hadron medium (largely a pion gas) at the end of the collision, which is
naturally small and increases with temperature in line with the gas density.
The physics in the quark-gluon plasma/liquid phase is less obvious, and here we
revisit a couple of simple estimates that suggest indeed that the
pomeron-mediated interactions are very relevant and should be included in
analysis of the jet quenching parameter. Finally, the ocasional hard collisions
produce features characteristic of a L\`evy flight in the q_perp^2 plane
perpendicular to the jet axis. We suggest one- and two-particle q_perp
correlations as interesting experimental probes.Comment: 14 pages, 16 figure
Improving Third-Party Relaying for LTE-A: A Realistic Simulation Approach
In this article we propose solutions to diverse conflicts that result from
the deployment of the (still immature) relay node (RN) technology in LTE-A
networks. These conflicts and their possible solutions have been observed by
implementing standard-compliant relay functionalities on the Vienna simulator.
As an original experimental approach, we model realistic RN operation, taking
into account that transmitters are not active all the time due to half-duplex
RN operation. We have rearranged existing elements in the simulator in a manner
that emulates RN behavior, rather than implementing a standalone brand-new
component for the simulator. We also study analytically some of the issues
observed in the interaction between the network and the RNs, to draw
conclusions beyond simulation observation.
The main observations of this paper are that: ) Additional time-varying
interference management steps are needed, because the LTE-A standard employs a
fixed time division between eNB-RN and RN-UE transmissions (typical relay
capacity or throughput research models balance them optimally, which is
unrealistic nowadays); ) There is a trade-off between the time-division
constraints of relaying and multi-user diversity; the stricter the constraints
on relay scheduling are, the less flexibility schedulers have to exploit
channel variation; and ) Thee standard contains a variety of parameters
for relaying configuration, but not all cases of interest are covered.Comment: 17 one-column pages, 9 figures, accepted for publication in IEEE ICC
2014 MW
Relativistic Many-Body Hamiltonian Approach to Mesons
We represent QCD at the hadronic scale by means of an effective Hamiltonian,
, formulated in the Coulomb gauge. As in the Nambu-Jona-Lasinio model,
chiral symmetry is explicity broken, however our approach is renormalizable and
also includes confinement through a linear potential with slope specified by
lattice gauge theory. This interaction generates an infrared integrable
singularity and we detail the computationally intensive procedure necessary for
numerical solution. We focus upon applications for the and quark
flavors and compute the mass spectrum for the pseudoscalar, scalar and vector
mesons. We also perform a comparative study of alternative many-body techniques
for approximately diagonalizing : BCS for the vacuum ground state; TDA and
RPA for the excited hadron states. The Dirac structure of the field theoretical
Hamiltonian naturally generates spin-dependent interactions, including tensor,
spin-orbit and hyperfine, and we clarify the degree of level splitting due to
both spin and chiral symmetry effects. Significantly, we find that roughly
two-thirds of the - mass difference is due to chiral symmetry and
that only the RPA preserves chiral symmetry. We also document how hadronic mass
scales are generated by chiral symmetry breaking in the model vacuum. In
addition to the vacuum condensates, we compute meson decay constants and detail
the Nambu-Goldstone realization of chiral symmetry by numerically verifying the
Gell-Mann-Oaks-Renner relation. Finally, by including D waves in our charmonium
calculation we have resolved the anomalous overpopulation of states
relative to observation
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