19,237 research outputs found
Macroscopic Quantum Tunneling and the "cosmic" Josephson effect
We discuss the possible influence of a cosmic magnetic field on the
macroscopic quantum tunneling process associated, in a cosmological context, to
the decay of the "false vacuum." We find a close analogy with the effects of an
external magnetic field applied to a Josephson junction in the context of
low-temperature/high-temperature superconducting devices.Comment: 4 pages, 1 pdf figure. Added references and an inset in Fig. 1,
results unchanged. To appear in Phys. Rev. D (Brief Report
Double Transverse-Spin Asymmetries in Drell-Yan Processes with Antiprotons
We present next-to-leading order predictions for double transverse-spin
asymmetries in Drell--Yan dilepton production initiated by proton--antiproton
scattering. The kinematic region of the proposed PAX experiment at GSI:
30\lesssim{s}\lesssim200\GeV^2 and 2\lesssim{M}\lesssim7\GeV is examined.
The Drell--Yan asymmetries turn out to be large, in the range 20--40%.
Measuring these asymmetries would provide the cleanest determination of the
quark transversity distributions.Comment: 11 pages, 7 figures, uses elsart and feynmp (included); one new
reference adde
The Zeta Function Method and the Harmonic Oscillator Propagator
We show how the pre-exponential factor of the Feynman propagator for the
harmonic oscillator can be computed by the generalized -function method.
Besides, we establish a direct equivalence between this method and Schwinger's
propertime method.Comment: 12 latex pages, no figure
The One Dimensional Damped Forced Harmonic Oscillator Revisited
In this paper we give a general solution to the problem of the damped
harmonic oscillator under the influence of an arbitrary time-dependent external
force. We employ simple methods accessible for beginners and useful for
undergraduate students and professors in an introductory course of mechanics.Comment: 4 Latex page
Recommended from our members
A management architecture for active networks
In this paper we present an architecture for network and applications management, which is based on the Active Networks paradigm and shows the advantages of network programmability. The stimulus to develop this architecture arises from an actual need to manage a cluster of active nodes, where it is often required to redeploy network assets and modify nodes connectivity. In our architecture, a remote front-end of the managing entity allows the operator to design new network topologies, to check the status of the nodes and to configure them. Moreover, the proposed framework allows to explore an active network, to monitor the active applications, to query each node and to install programmable traps. In order to take advantage of the Active Networks technology, we introduce active SNMP-like MIBs and agents, which are dynamic and programmable. The programmable management agents make tracing distributed applications a feasible task. We propose a general framework that can inter-operate with any active execution environment. In this framework, both the manager and the monitor front-ends communicate with an active node (the Active Network Access Point) through the XML language. A gateway service performs the translation of the queries from XML to an active packet language and injects the code in the network. We demonstrate the implementation of an active network gateway for PLAN (Packet Language for Active Networks) in a forty active nodes testbed. Finally, we discuss an application of the active management architecture to detect the causes of network failures by tracing network events in time
Charged currents, color dipoles and xF_3 at small x
We develop the light-cone color dipole description of highly asymmetric
diffractive interactions of left-handed and right-handed electroweak bosons. We
identify the origin and estimate the strength of the left-right asymmetry
effect in terms of the light-cone wave functions. We report an evaluation of
the small-x neutrino-nucleon DIS structure functions xF_3 and 2xF_1 and present
comparison with experimental data.Comment: 11 pages, 3 figures, misprints correcte
Diagnostics for specific PAHs in the far-IR: searching neutral naphthalene and anthracene in the Red Rectangle
Context. In the framework of the interstellar polycyclic aromatic
hydrocarbons (PAHs) hypothesis, far-IR skeletal bands are expected to be a
fingerprint of single species in this class. Aims. We address the question of
detectability of low energy PAH vibrational bands, with respect to spectral
contrast and intensity ratio with ``classical'' Aromatic Infrared Bands (AIBs).
Methods. We extend our extablished Monte-Carlo model of the photophysics of
specific PAHs in astronomical environments, to include rotational and
anharmonic band structure. The required molecular parameters were calculated in
the framework of the Density Functional Theory. Results. We calculate the
detailed spectral profiles of three low-energy vibrational bands of neutral
naphthalene, and four low-energy vibrational bands of neutral anthracene. They
are used to establish detectability constraints based on intensity ratios with
``classical'' AIBs. A general procedure is suggested to select promising
diagnostics, and tested on available Infrared Space Observatory data for the
Red Rectangle nebula. Conclusions. The search for single, specific PAHs in the
far-IR is a challenging, but promising task, especially in view of the
forthcoming launch of the Herschel Space Observatory.Comment: 13 pages, 13 figures, accepted for publication in A&
Observation of a New Fluxon Resonant Mechanism in Annular Josephson Tunnel Structures
A novel dynamical state has been observed in the dynamics of a perdurbed
sine-Gordon system. This resonant state, has been experimentally observed as a
singularity in the dc current voltage characteristic of an annular Josephson
tunnel junction, excited in the presence of a magnetic field. With this
respect, it can be assimilated to self-resonances known as Fiske steps.
Differently from these, however, we demonstrate, on the basis of numerical
simulations, that its detailed dynamics involves rotating fluxon pairs, a
mechanism associated, so far, to self-resonances known as zero-field steps.Comment: 4 pages, 2 figures, submitted to Physical Review Letter
- …