* Astronomy

Members Login
Post Info
TOPIC: Lorentz invariance


L

Posts: 131433
Date:
Lorentz Violation
Permalink  
 


Title: New Limits on Planck Scale Lorentz Violation from Gamma-ray Burst Polarization
Authors: Floyd W. Stecker
(Version v2)

Constraints on possible Lorentz invariance violation to first order in E/M_{Planck} for photons in the framework of effective field theory are discussed. Using the detection of polarized soft gamma-ray emission from the gamma-ray burst GRB041219a that indicates the absence of vacuum birefringence, together with a method for estimating the redshift of the burst, we improve the previous constraints on the dimension 5 Lorentz violating modification to the Lagrangian of an effective local QFT for QED by more than 4 orders of magnitude, |xi| < 8.3 x 10^{-14}.

Read more (7kb, PDF)

__________________


L

Posts: 131433
Date:
Permalink  
 

Title: Lorentz Violation: Motivation and new constraints
Authors: Stefano Liberati (SISSA, Trieste and INFN, Trieste), Luca Maccione (DESY, Hamburg)

We review the main theoretical motivations and observational constraints on Planck scale suppressed violations of Lorentz invariance. After introducing the problems related to the phenomenological study of quantum gravitational effects, we discuss the main theoretical frameworks within which possible departures from Lorentz invariance can be described. In particular, we focus on the framework of Effective Field Theory, describing several possible ways of including Lorentz violation therein and discussing their theoretical viability. We review the main low energy effects that are expected in this framework. We discuss the current observational constraints on such a framework, focusing on those achievable through high-energy astrophysics observations. In this context we present a summary of the most recent and strongest constraints on QED with Lorentz violating non-renormalisable operators. Finally, we discuss the present status of the field and its future perspectives.

Read more  (66kb, PDF)

__________________


L

Posts: 131433
Date:
Lorentz Invariance Violation
Permalink  
 


Title: Lorentz Invariance Violation and the Observed Spectrum of Ultrahigh Energy Cosmic Rays
Authors: S. T. Scully (JMU), F. W. Stecker (NASA/GSFC)
(Version v3)

There has been much interest in possible violations of Lorentz invariance, particularly motivated by quantum gravity theories. It has been suggested that a small amount of Lorentz invariance violation (LIV) could turn off photomeson interactions of ultrahigh energy cosmic rays (UHECRs) with photons of the cosmic background radiation and thereby eliminate the resulting sharp steepening in the spectrum of the highest energy CRs predicted by Greisen Zatsepin and Kuzmin (GZK). Recent measurements of the UHECR spectrum reported by the HiRes and Auger collaborations, however, indicate the presence of the GZK effect. We present the results of a detailed calculation of the modification of the UHECR spectrum caused by LIV using the formalism of Coleman and Glashow. We then compare these results with the experimental UHECR data from Auger and HiRes. Based on these data, we find a best fit amount of LIV of 4.5^{+1.5}_{-4.5} x  10^{-23},consistent with an upper limit of 6 x 10^{-23}. This possible amount of LIV can lead to a recovery of the cosmic ray spectrum at higher energies than presently observed. Such an LIV recovery effect can be tested observationally using future detectors.

Read more (427kb, PDF)

__________________


L

Posts: 131433
Date:
Permalink  
 

Title: Lorentz Invariance Violation and the Observed Spectrum of Ultrahigh Energy Cosmic Rays
Authors: S. T. Scully (JMU), F. W. Stecker (NASA/GSFC)
(Version v2)

There has been much interest in possible violations of Lorentz invariance, particularly motivated by quantum gravity theories. It has been suggested that a small amount of Lorentz invariance violation (LIV) could turn off photomeson interactions of ultrahigh energy cosmic rays (UHECRs) with photons of the cosmic background radiation and thereby eliminate the resulting sharp steepening in the spectrum of the highest energy CRs predicted by Greisen Zatsepin and Kuzmin (GZK). Recent measurements of the UHECR spectrum reported by the HiRes and Auger collaborations, however, indicate the presence of the GZK effect. We present the results of a detailed calculation of the modification of the UHECR spectrum caused by LIV using the formalism of Coleman and Glashow. We then compare these results with the experimental UHECR data from Auger and HiRes. Based on these data, we find a best fit amount of LIV of 4.5^{+1.5}_{-4.5} x 10^{-23},consistent with an upper limit of 6 x 10^{-23}. This possible amount of LIV can lead to a recovery of the cosmic ray spectrum at higher energies than presently observed. Such an LIV recovery effect can be tested observationally using future detectors.

Read more (764kb, PDF)

__________________


L

Posts: 131433
Date:
Lorentz violations
Permalink  
 


Physicists at Indiana University have developed a promising new way to identify a possible abnormality in a fundamental building block of Einstein's theory of relativity known as "Lorentz invariance." If confirmed, the abnormality would disprove the basic tenet that the laws of physics remain the same for any two objects travelling at a constant speed or rotated relative to one another.
IU distinguished physics professor Alan Kostelecky and graduate student Jay Tasson take on the long-held notion of the exact symmetry promulgated in Einstein's 1905 theory and show in a paper to be published in the Jan. 9 issue of Physical Review Letters that there may be unexpected violations of Lorentz invariance that can be detected in specialised experiments.

"It is surprising and delightful that comparatively large relativity violations could still be awaiting discovery despite a century of precision testing. Discovering them would be like finding a camel in a haystack instead of a needle" - Alan Kostelecky.

If the findings help reveal the first evidence of Lorentz violations, it would prove relativity is not exact. Space-time would not look the same in all directions and there would be measurable relativity violations, however minuscule.

Read more

Title: Prospects for Large Relativity Violations in Matter-Gravity Couplings
Authors: V. Alan Kostelecký and Jay D. Tasson

Deviations from relativity are tightly constrained by numerous experiments. A class of unmeasured and potentially large violations is presented that can be tested in the laboratory only via weak-gravity couplings. Specialised highly sensitive experiments could achieve measurements of the corresponding effects. A single constraint of 1 x 10^-11 GeV is extracted on one combination of the 12 possible effects in ordinary matter. Estimates are provided for attainable sensitivities in existing and future experiments.

Read more

__________________


L

Posts: 131433
Date:
Lorentz invariance
Permalink  
 


Physicists working to disprove "Lorentz invariance" -- Einstein's prediction that matter and massless particles will behave the same no matter how they're turned or how fast they go -- won't get that satisfaction from muon neutrinos, at least for the time being, says a consortium of scientists.
The test of Lorentz invariance, conducted by MINOS Experiment scientists and reported in the Oct. 10 issue of Physical Review Letters, started with a stream of muon neutrinos produced at Fermilab particle accelerator, near Chicago, and ended with a neutrino detector 750 meters away and 103 meters below ground. As the Earth does its daily rotation, the neutrino beam rotates too.

Read more

__________________
Page 1 of 1  sorted by
Quick Reply

Please log in to post quick replies.



Create your own FREE Forum
Report Abuse
Powered by ActiveBoard