63 research outputs found
Testing Lorentz Invariance with Neutrinos
Get PDFThe search for a theory that unifies general relativity and quantum theory
has focused attention on models of physics at the Planck scale. One possible
consequence of models such as string theory may be that Lorentz invariance is
not an exact symmetry of nature. We discuss here some possible experimental and
observational tests of Lorentz invariance involving neutrino physics and
astrophysics.Comment: 34 pages, 10 figures, typos in Apx.A corrected. To be published in
Neutrino Physics and Astrophysics, edited by F. W. Stecker, in the
Encyclopedia of Cosmology Series II, edited by G. G. Fazio, World Scientific
Publishing Company, Singapore, 2023. arXiv admin note: text overlap with
arXiv:1705.08485, arXiv:1708.05672, arXiv:1411.588
Stellar Photon Archaeology with Gamma-Rays
No full textOngoing deep surveys of galaxy luminosity distribution functions, spectral energy distributions and backwards evolution models of star formation rates can be used to calculate the past history of intergalactic photon densities and, from them, the present and past optical depth of the Universe to gamma-rays from pair production interactions with these photons. The energy-redshift dependence of the optical depth of the Universe to gamma-rays has become known as the Fazio-Stecker relation (Fazio & Stecker 1970). Stecker, Malkan & Scully have calculated the densities of intergalactic background light (IBL) photons of energies from 0.03 eV to the Lyman limit at 13.6 eV and for 06, using deep survey galaxy observations from Spitzer, Hubble and GALEX and have consequently predicted spectral absorption features for extragalactic gamma-ray sources. This procedure can also be reversed. Determining the cutoff energies of gamma-ray sources with known redshifts using the recently launched Fermi gamma-ray space telescope may enable a more precise determination of the IBL photon densities in the past, i.e., the "archaeo-IBL.", and therefore allow a better measure of the past history of the total star formation rate, including that from galaxies too faint to be observed
Extragalactic Backgrounds in the Far UV and Exploring Star Formation at High Redshifts with Gamma-ray Observations
No full textThe determination of the intergalactic photon densities from the FIR to the UV which is produced by stellar emission and dust reradiation at various redshifts can provide an independent measure of the star formation history of the universe. Using recent Spitzer and GALEX data in conjunction with other observational inputs, Stecker, Malkan and Scully have calculated the intergalactic photon density as a function of both energy and redshift for 0 < zeta < 6 for photon energies from 0.003 eV to the Lyman limit cutoff at 13.6 eV in a ACDM universe with Omega(sub Lambda) = 0.7 and Omega(sub m) = 0.3. Their results are based on backwards evolution models for galaxies which were developed by Malkan and Stecker previously. The calculated background SEDs at zeta = 0 are in good agreement with the present observational data and limits. The calculated intergalactic photon densities as a function of redshift were used to predict to extend the absorption of high energy 7-rays in intergalactic space from sources such as blazars and quasars, this absorption being produced by interactions the y-rays with the intergalactic FIR-UV photons having the calculated densities. The results are in excellent agreement with absorption features found in the low gamma-ray spectra of Mkn 421, Mkn 501 at, zeta = 0.03 and PK
High-Energy Neutrinos from Active Galactic Nuclei
Get PDFActive Galactic Nuclei (AGN) are sources of high-energy gamma-rays and are
considered to be promising candidates to be sources of high-energy cosmic rays
and neutrinos as well. We present and discuss various models for ion
acceleration and their interactions with matter and radiation leading to
high-energy neutrino production. We consider neutrino production mechanisms in
both jet-loud and jet-quiet AGN, focusing on disks and coronae in the vicinity
of the central black hole, jet regions, and magnetized environments surrounding
the AGN. The IceCube Collaboration has reported high-energy neutrino events
that may come from both the jet-loud AGN TXS 0506+056 and the jet-quiet AGN NGC
1068. We discuss the implications of these observations themselves as well as
the the origins of the all-sky neutrino intensity.Comment: 58 pages, 26 figures, 1 table, invited review article to appear in
"Neutrino Physics and Astrophysics", Ed. F. W. Stecker, in Encyclopedia of
Cosmology II, Ed. G. G. Fazio (World Scientific), references adde
Searching for traces of Planck-scale physics with high energy neutrinos
No full textHigh-energy cosmic neutrino observations provide a sensitive test of Lorentz invariance violation (LIV), which may be a consequence of quantum gravity theories. We consider a class of nonrenormalizable, Lorentz invariance violating operators that arise in an effective field theory (EFT) description of Lorentz invariance violation in the neutrino sector inspired by Planck-scale physics and quantum gravity models. We assume a conservative generic scenario for the redshift distribution of extragalactic neutrino sources and employ Monte Carlo techniques to describe superluminal neutrino propagation, treating kinematically allowed energy losses of superluminal neutrinos caused by both vacuum pair emission (VPE) and neutrino splitting. We consider EFTs with both nonrenormalizable CPT -odd and nonrenormalizable CPT -even operator dominance. We then compare the spectra derived using our Monte Carlo calculations in both cases with the spectrum observed by IceCube in order to determine the implications of our results regarding Planck-scale physics. We find that if the dropoff in the neutrino flux above similar to 2 PeV is caused by Planck-scale physics, rather than by a limiting energy in the source emission, a potentially significant pileup effect would be produced just below the dropoff energy in the case of CPT -even operator dominance. However, such a clear dropoff effect would not be observed if the CPT -odd, CPT -violating term dominates
Testing Lorentz Symmetry Using High Energy Astrophysics Observations
Get PDFWe discuss some of the tests of Lorentz symmetry made possible by astrophysical observations of ultrahigh energy cosmic rays, gamma-rays, and neutrinos. These are among the most sensitive tests of Lorentz invariance violation because they are the highest energy phenomena known to man
Implications of the IRAS data for galactic gamma-ray astronomy and EGRET
Get PDFUsing the results of gamma-ray, millimeter wave and far infrared surveys of the galaxy, one can derive a logically consistent picture of the large scale distribution of galactic gas and cosmic rays, one tied to the overall processes of stellar birth and destruction on a galactic scale. Using the results of the IRAS far-infrared survey of the galaxy, the large scale radial distribution of galactic far-infrared emission were obtained independently for both the Northern and Southern Hemisphere sides of the Galaxy. It was found that the dominant feature in these distributions to be a broad peak coincident with the 5 kpc molecular gas cloud ring. Also found was evidence of spiral arm features. Strong correlations are evident between the large scale galactic distributions of far infrared emission, gamma-ray emission and total CO emission. There is a particularly tight correlation between the distribution of warm molecular clouds and far-infrared emission on a galactic scale
High Energy Astrophysics Tests of Lorentz Invariance and Quantum Gravity Models
Get PDFHigh-energy astrophysics observations provide the best possibilities to detect a very small violation of Lorentz invariance such as may be related to the structure of space-time near the Planck scale of approximately 10-35 m. I will discuss here the possible signatures of Lorentz invariance violation (LIV) from observations of the spectra, polarization, and timing of gamma-rays from active galactic nuclei and gamma-ray bursts. Other sensitive tests are provided by observations ofthe spectra of ultrahigh energy cosmic rays and neutrinos. Using the latest data from the Pierre Auger Observatory one can already derive an upper limit of 4.5 x 10(exp -23) to the amount of LIV at a proton Lorentz factor of -2 x 10(exp 11). This result has fundamental implications for quantum gravity models. I will also discuss the possibilities of using more sensitive space based detection techniques to improve searches for LIV in the future
A New Limit on Planck Scale Lorentz Violation from Gamma-ray Burst Polarization
Get PDFConstraints on possible Lorentz invariance violation (UV) to first order in E/M(sub Plank) for photons in the framework of effective field theory (EFT) are discussed, taking cosmological factors into account. Then. using the reported detection of polarized soft gamma-ray emission from the gamma-ray burst GRB041219a that is indicative' of an absence of vacuum birefringence, together with a very recent improved method for estimating the redshift of the burst, we derive constraints on the dimension 5 Lorentz violating modification to the Lagrangian of an effective local QFT for QED. Our new constraints are more than five orders of magnitude better than recent constraints from observations of the Crab Nebula.. We obtain the upper limit on the Lorentz violating dimension 5 EFT parameter absolute value of zeta of 2.4 x 10(exp -15), corresponding to a constraint on the dimension 5 standard model extension parameter. Kappa (sup 5) (sub (v)oo) much less than 4.2 X 10(exp -3)4 / GeV
Limiting Superluminal Electron and Neutrino Velocities Using the 2010 Crab Nebula Flare and the IceCube PeV Neutrino Events
Get PDFThe observation of two PetaelectronVolt (PeV)-scale neutrino events reported by Ice Cube allows one to place constraints on Lorentz invariance violation (LIV) in the neutrino sector. After first arguing that at least one of the PetaelectronVolt IceCube events was of extragalactic origin, I derive an upper limit for the difference between putative superluminal neutrino and electron velocities of less than or equal to approximately 5.6 x 10(exp -19) in units where c = 1, confirming that the observed PetaelectronVolt neutrinos could have reached Earth from extragalactic sources. I further derive a new constraint on the superluminal electron velocity, obtained from the observation of synchrotron radiation from the Crab Nebula flare of September, 2010. The inference that the greater than 1 GigaelectronVolt gamma-rays from synchrotron emission in the flare were produced by electrons of energy up to approx. 5.1 PetaelectronVolt indicates the nonoccurrence of vacuum Cerenkov radiation by these electrons. This implies a new, strong constraint on superluminal electron velocities delta(sub e) less than or equal to approximately 5 x 10(exp -21). It immediately follows that one then obtains an upper limit on the superluminal neutrino velocity alone of delta(sub v) less than or equal to approximately 5.6 x 10(exp -19), many orders of magnitude better than the time-of-flight constraint from the SN1987A neutrino burst. However, if the electrons are subluminal the constraint on the absolute value of delta(sub e) less than or equal to approximately 8 x 10(exp -17), obtained from the Crab Nebula gamma-ray spectrum, places a weaker constraint on superluminal neutrino velocity of delta(sub v) less than or equal to approximately 8 x 10(exp -17)
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