Decoherence due to thermal effects in two quintessential quantum systems

Decoherence effects at finite temperature (T) are examined for two manifestly quantum systems: (i) Casimir forces between parallel plates that conduct along different directions, and (ii) a topological Aharonov-Bohm (AB) type force between fluxons in a superconductor. As we illustrate, standard path integral calculations suggest that thermal effects may remove the angular dependence of the Casimir force in case (i) with a decoherence time set by h/(k_{B} T) where h is Plank's constant and k_{B} is the Boltzmann constant. This prediction may be tested. The effect in case (ii) is due a phase shift picked by unpaired electrons upon encircling an odd number of fluxons. In principle, this effect may lead to small modifications in Abrikosov lattices. While the AB forces exist at extremely low temperatures, we find that thermal decoherence may strongly suppress the topological force at experimentally pertinent finite temperatures. It is suggested that both cases (i) and (ii) (as well as other examples briefly sketched) are related to a quantum version of the fluctuation-dissipation theorem.Comment: 15 pages, 2 figure

Now You See It, Now You Don't--The Pattern of Production of Certain Resonances

We try to motivate from QCD a pattern of production in various reactions of (non)exotic resonances. A higher penalty for extra q\bar{q} production in e^+ e^- collisions than in collisions with a nucleon target may explain the absence of exotic multi-quark states in e^+ e^- . We also briefly address the doubly-charmed baryons and the utilization of QCD inequalities in connection with possible new hadronic states.Comment: 11 page

Signs and Polarized/Magnetic versions of the Casimir Forces

We consider versions of the Casimir effect where the force can be controlled by changing the angle between two Casimir ``plates'' or the temperature of two nearby rings. We also present simple arguments for the sign of Casimir forces.Comment: 3 pages of double column revtex, + 4 figures. For correspondence use Tel Aviv address, or [email protected]

Some Comments on the Putative Θ+\Theta^ + (1543) Exotic State

We point out that existing $K^+d$ scattering data available in the PDG (Particle Data Group compilation) suggest some fluctuations in those momentum bins where the (Fermi motion broadened) $\Theta^+$[1543] resonance recently indicated in many gamma nuclear reactions and predicted six years ago by Diakonv Petrov and Polyakov might have shown up. The I=0, $J^P={1/2}^+$ P-wave channel should have a universal peak cross section of $\sim 37$ mb at resonance. The smallness of the effect seen in $K^+d$ with the $\delta \sigma$ fluctuations being less than 4 mb imply an indirect bound $\Gamma_{\Theta^+} < 6$ MeV, far stronger than the direct gamma-d measurements. This renders the theoretical interpretation of the new state very difficult.Comment: 10 pages, no figures, RevTex

QCD Inequalities and the Ds(2320)D_s(2320)

We discuss the new state $D_{sJ}(2317)$ discovered by BaBar and demonstrate using QCD inequalities that if indeed the $f_0(980)$ and the new $D_{sJ}(2317)$ ($0^+$) are primarilly made of four quarks that a new I=0 ``$\bar DD$ bound state'' at a mass smaller than 3660 MeV must exist. Observation of such a state will constitute definitive evidence for four-quark states

Correlated Scattering and Cluster Planes

We suggest a new correlation in diffractive production of 2 ``clusters'' $A+B\to A^\ast B^\ast$ with large intrinsic angular momenta for each $A^\ast$ and $B^\ast$ cluster. These correlations are expected in the context of the ``color dipole picture'' for high energy collision and reflect the approximate conservation of dipole direction during the collision. This conservation is in particular manifest when the two dipoles, $\vec d_A$, $\vec d_B$ and the impact vector \undtilb are all parallel. The predicted positive triple correlation is between the momentum transfer \undtildel and the planes of the $A^\ast$ and $B^\ast$ clusters.Comment: 8 pages, late

Testing Violations of Lorentz Invariance with Cosmic Rays

Cosmic rays are the highest energy particles available for our study and as such serve as excellent probes of the effects of Lorentz Invariance Violations, which are expected to increase with energy. This general paradigm is investigated in this paper by studying the effects of such violations within the Coleman-Glashow model in which each particle species may have its own maximum attainable velocity, even exceeding that of light \textit{in vacuo}. The particular focus here is that the muon neutrino may have the maximum speed exceeding that of light. We show that such an assumption leads to the elongation of the decay lifetime of the pion that increases with energy over and above the time dilation effects. We provide a transparent analytical derivation of the spectral intensities of muon neutrinos and muons generated in the Earth's atmosphere by cosmic rays. In this derivation we not only account for elongation of the pion lifetime, but also for the loss of energy by the neutrinos by radiation of the electron-positron pairs through the Cohen-Glashow process, during their propagation. We then compare the theoretical spectra with observations of neutrinos and muons from large instruments like IceCube and BUST to set a limit of $\sim10^{-13}$ on the fractional excess speed of neutrinos over that of light. We also show that the ratio of the spectral intensities of downward and upward moving neutrinos at various angles constitute a diagnostic exclusively for the Cohen-Glashow process, which may be searched for in the IceCube data set. We conclude the paper with several comments, including those related to improvements of these tests when definite signals of GZK neutrinos will be observed.Comment: version 2, 28 pages, 10 figure

Some Speculations on the Ultimate Planck Energy

The inability to achieve in the present universe, via electromagnetic or gravitational acceleration, Planck energies for elementary particles is suggested on the basis of several, some relatively sophisticated, failed attempts. This failure is essential for schemes were the superplanckian regime for the energies of elementary particles is ``Unphysical''. The basic observation is that this failure to achieve superplanckian energies naturally occurs in our universe of finite age and horizon. It does tie up in a mysterious fashion these cosmological quantities and elementary physics parameters such as the masses of the lightest charged fermions.Comment: 11 pages, latex, 4 figures. For ALL CORRESPONDENCE contact [email protected]

Are there non-strange low-lying penta-quarks and can we understand their width

We argue that the lightest isospin 1/2 partners of the Z^+(1530) s(bar)uudd penta-quark predicted by Diakonov, Petrov and Polyakov are not the N(1710) mixed anti-decuplet states, but the pure non-strange u(bar)(ud)(ud) and d(bar)(ud)(ud) penta-quark states which may lie as low as 1200 MeV. The expected low width of a few MeV of such a putative state may explain why it was missed in phase shift analyzes of pion-nucleon scattering.Comment: 11 pages, 1 figur

Bimaximal Neutrino Mixing and Neutrino Mass Matrix

We show that the bimaximal neutrino mixing pattern suggested by the solar and atmospheric neutrino data can be derived from the maximal, symmetric, four neutrino mixing in the limit that one of the neutrinos is made heavy. Imposing the constraints of no neutrinoless double beta decay and a 20% hot dark matter component of the universe leads to a three neutrino mass matrix recently suggested by Georgi and Glashow. Our result can be useful in constructing theoretical models for the bimaximal pattern. We illustrate this by a simple example.Comment: New material strengthening the argument of the paper added; 10 pages latex; UMD-PP-99-2