Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userComment on Noncommutativity as a Possible Origin of the Ultrahigh-energy Cosmic Ray and the TeV Photon Paradoxes
51
0
0.0
(
0
)
Authors
Cosmas Zachos
Ask ChatGPT about the research
No Arabic abstract
A Lorentz-noninvariant modification of the kinematic dispersion law was proposed in [hep-th/0211237], claimed to be derivable from from q-deformed noncommutative theory, and argued to evade ultrahigh energy threshold anomalies (trans-GKZ-cutoff cosmic rays and TeV-photons) by raising the respective thresholds. It is pointed out that such dispersion laws do not follow from deformed oscillator systems, and the proposed dispersion law is invalidated by tachyonic propagation, as well as photon instability, in addition to the process considered.
rate research
Read More
In this work, we comment on two special points in the paper by S. Ghosh [Phys. Rev. D 74, 084019 (2006)]. First of all, the Lagrangian presented by the author does not describe the Magueijo- Smolin model of Doubly Special Relativity since it is equivalent to the Lagrangian of the standard free relativistic particle. We also show that the introduction of noncommutative structures is not relevant to the problem of Lorentz covariance in Ghosh formalism.
We explain the observed multiwavelength photon spectrum of a number of BL Lac objects detected at very high energy (VHE, $E gtrsim 30$ GeV), using a lepto-hadronic emission model. The one-zone leptonic emission is employed to fit the synchrotron peak. Subsequently, the SSC spectrum is calculated, such that it extends up to the highest energy possible for the jet parameters considered. The data points beyond this energy, and also in the entire VHE range are well explained using a hadronic emission model. The ultrahigh-energy cosmic rays (UHECRs, $Egtrsim 0.1$ EeV) escaping from the source interact with the extragalactic background light (EBL) during propagation over cosmological distances to initiate electromagnetic cascade down to $sim1$ GeV energies. The resulting photon spectrum peaks at $sim1$ TeV energies. We consider a random turbulent extragalactic magnetic field (EGMF) with a Kolmogorov power spectrum to find the survival rate of UHECRs within 0.1 degrees of the direction of propagation in which the observer is situated. We restrict ourselves to an RMS value of EGMF, $B_{rm rms}sim 10^{-5}$ nG, for a significant contribution to the photon spectral energy distribution (SED) from UHECR interactions. We found that UHECR interactions on the EBL and secondary cascade emission can fit gamma-ray data from the BL Lacs we considered at the highest energies. The required luminosity in UHECRs and corresponding jet power are below the Eddington luminosities of the super-massive black holes in these BL Lacs.
We use a multimessenger approach to constrain realistic mixed composition models of ultrahigh energy cosmic ray sources using the latest cosmic ray, neutrino, and gamma-ray data. We build on the successful Unger-Farrar-Anchordoqui 2015 (UFA15) model which explains the shape of the spectrum and its complex composition evolution via photodisintegration of accelerated nuclei in the photon field surrounding the source. We explore the constraints which can currently be placed on the redshift evolution of sources and the temperature of the photon field surrounding the sources. We show that a good fit is obtained to all data either with a source which accelerates a narrow range of nuclear masses or a Milky Way-like mix of nuclear compositions, but in the latter case the nearest source should be 30-50 Mpc away from the Milky Way in order to fit observations from the Pierre Auger Observatory. We also ask whether the data allow for a subdominant purely protonic component at UHE in addition to the primary UFA15 mixed composition component. We find that such a two-component model can significantly improve the fit to cosmic ray data while being compatible with current multimessenger data.
The IceCube experiment recently detected the first flux of high-energy neutrinos in excess of atmospheric backgrounds. We examine whether these neutrinos originate from within the same extragalactic sources as ultrahigh-energy cosmic rays. Starting from rather general assumptions about spectra and flavors, we find that producing a neutrino flux at the requisite level through pion photoproduction leads to a flux of protons well below the cosmic-ray data at ~10^18 eV, where the composition is light, unless pions/muons cool before decaying. This suggests a dominant class of accelerator that allows for cosmic rays to escape without significant neutrino yields.
The total cosmic ray electron spectrum (electrons plus positrons) exhibits a break at a particle energy of $sim 1rm~TeV$ and extends without any attenuation up to $rm sim 20~ TeV $. Synchrotron and inverse Compton energy losses strongly constrain both the age and the distance of the potential sources of TeV and multi-TeV electrons to $rmapprox 10^5~yr$ and $rm approx 100-500~pc$, depending on both the absolute value and energy dependence of the cosmic ray diffusion coefficient. This suggests that only a few, or just one nearby discrete source may explain the observed spectrum of high energy electrons. On the other hand the measured positron fraction, after initially increasing with particle energy, saturates at a level well below 0.5 and likely drops above $sim 400-500$ GeV. This means that the local source(s) of TeV electrons should not produce positrons in equal amount, ruling out scenarios involving pulsars/pulsar winds as the main sources of high energy leptons. In this paper we show that a single, local, and fading source can naturally account for the entire spectrum of cosmic ray electrons in the TeV domain. Even though the nature of such source remains unclear, we discuss known cosmic ray accelerators, such as supernova remnant and stellar wind shocks, which are believed to accelerate preferentially electrons rather than positrons.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
