Related papers: Effect of Pions in Cosmic Rays
When photons propagate in vacuum they may fluctuate into matter pairs thus allowing the vacuum to be polarised. This linear effect leads to charge screening and renormalisation. When exposed to an intense background field a nonlinear effect…
The effect of static electromagnetic fields on the propagation of light is analyzed in the context of a particular class of scalar-tensor gravitational theories. It is found that for appropriate field configurations and light polarization,…
We argue that gamma-ray bursts (GRBs) may be the origin of the cosmic gamma-ray background radiation observed in GeV range. It has theoretically been discussed that protons may carry a much larger amount of energy than electrons in GRBs,…
We show theoretical results for $(\gamma, \pi^0 \pi^0)$ production on nucleons and nuclei in the kinematical region where the scalar isoscalar $\pi \pi$ amplitude is influenced by the $\sigma$ pole. The final state interaction of the pions…
EGRET data on the Gamma ray emission from the inner Galaxy have shown a rather flat spectrum, extending to about 50 GeV. It is usually assumed that these gamma-rays arise from the interactions of cosmic ray nuclei with ambient matter.…
Extremely strong magnetic fields change the vacuum index of refraction. Although this polarization dependent effect is small for typical neutron stars, it is large enough to decouple the polarization states of photons traveling within the…
The main motivation for our work has been a puzzling observation concerning quasars. No one expected the existence of correlations in the polarisation of visible light coming from objects separated by gigaparsecs, until they were first…
The leading-twist wave functions of the pion and the photon at a low normalization point are calculated in the effective low--energy theory derived from the instanton vacuum. The pion wave function is found to be close to the asymptotic…
The fragmentation of deuterons into pions emitted forward in the kinematic region forbidden for free nucleon-nucleon collisions is analyzed. The inclusive relativistic invariant spectrum of pions and the tensor analyzing power T_{20} are…
From the analysis of measurements of the linear polarisation of visible light coming from quasars, the existence of large-scale coherent orientations of quasar polarisation vectors in some regions of the sky has been reported. Here, we show…
The mixing of the photon with a hypothetical sterile paraphotonic state would have consequences on the cosmological propagation of photons. Observations of gamma-rays from active galactic nuclei in GLAST and MAGIC will open a new domain in…
By employing vector meson dominance to establish the electromagnetic interactions of hadrons, the electromagnetic self-energy of the neutral pions, which receives the contributions from the vector resonances due to chiral anomaly, is…
The response of the QED vacuum in an asymptotically large electromagnetic field is studied. In this regime the vacuum energy is strongly influenced by the vacuum polarization effect. The possible interaction between the virtual…
This work establishes a relation between chiral anomalies in curved spacetimes and the radiative content of the gravitational field. In particular, we show that a flux of circularly polarized gravitational waves triggers the spontaneous…
We study the dependence of quark condensate $\Sigma$ on an external magnetic field. For weak fields, it rises linearly with the field. Pion mass and residue are also shifted so that the Gell-Mann - Oakes - Renner relation is satisfied. In…
It is known that vacuum polarization can modify the photon propagation modes in the atmospheric plasma of a strongly magnetized neutron star. A resonance occurs when the effect of vacuum polarization on the photon modes balances that of the…
The association of all three soft gamma-ray repeaters (SGRs) with supernova remnants has made possible estimates of the distance to and luminosity of the sources of SGRs, which have provided a starting point for detailed modeling. One of…
We investigate the effect of the density-dependent proton and neutron gaps on vortex dynamics in neutron stars. We argue that the persistence of neutron star magnetic fields on timescales of $10^9$ y suggests a superconducting gap curve…
The influence of the strong laser-driven vacuum on a propagating electromagnetic probe wave has been studied in detail. We investigate two scenarios comprising a focused probe laser beam passing through a region of vacuum polarised by an…
This is the first of a series of papers devoted to a detailed analysis of isospin-breaking effects in the $\pi \pi$ scattering amplitude and the vector form factor of the pion. Isospin breaking originates from the mass difference between up…