Constraints and tests of the OPERA superluminal neutrinos

Lorentz Symmetry Violation of Cosmic Photons

As a basic symmetry of space-time, Lorentz symmetry has played important roles in various fields of physics, and it is a glamorous question whether Lorentz symmetry breaks. Since Einstein proposed special relativity, Lorentz symmetry has withstood very strict tests, but there are still motivations for Lorentz symmetry violation (LV) research from both theoretical consideration and experimental feasibility, that attract physicists to work on LV theories, phenomena and experimental tests with enthusiasm. There are many theoretical models including LV effects, and different theoretical models predict different LV phenomena, from which we can verify or constrain LV effects. Here, we introduce three types of LV theories: quantum gravity theory, space-time structure theory and effective field theory with extra-terms. Limited by the energy of particles, the experimental tests of LV are very difficult; however, due to the high energy and long propagation distance, high-energy particles from astronomical sources can be used for LV phenomenological researches. Especially with cosmic photons, various astronomical observations provide rich data from which one can obtain various constraints for LV researches. Here, we review four common astronomical phenomena which are ideal for LV studies, together with current constraints on LV effects of photons.

Astrophysical Neutrinos in Testing Lorentz Symmetry

An overview of searches related to neutrinos of astronomical and astrophysical origin performed within the framework of the Standard-Model Extension is provided. For this effective field theory, key definitions, intriguing physical consequences, and the mathematical formalism are summarized within the neutrino sector to search for effects from a background that could lead to small deviations from Lorentz symmetry. After an introduction to the fundamental theory, examples of various experiments within the astronomical and astrophysical context are provided. Order-of-magnitude bounds of SME coefficients are shown illustratively for the tight constraints that this sector allows us to place on such violations.

Closing the Door on Quantum Nonlocality

Bell-type inequalities are proven using oversimplified probabilistic models and/or counterfactual definiteness (CFD). If setting-dependent variables describing measuring instruments are correctly introduced, none of these inequalities may be proven. In spite of this, a belief in a mysterious quantum nonlocality is not fading. Computer simulations of Bell tests allow people to study the different ways in which the experimental data might have been created. They also allow for the generation of various counterfactual experiments’ outcomes, such as repeated or simultaneous measurements performed in different settings on the same “photon-pair”, and so forth. They allow for the reinforcing or relaxing of CFD compliance and/or for studying the impact of various “photon identification procedures”, mimicking those used in real experiments. Data samples consistent with quantum predictions may be generated by using a specific setting-dependent identification procedure. It reflects the active role of instruments during the measurement process. Each of the setting-dependent data samples are consistent with specific setting-dependent probabilistic models which may not be deduced using non-contextual local realistic or stochastic hidden variables. In this paper, we will be discussing the results of these simulations. Since the data samples are generated in a locally causal way, these simulations provide additional strong arguments for closing the door on quantum nonlocality.

What do we know about Lorentz invariance?

The realization that Planck-scale physics can be tested with existing technology through the search for spacetime-symmetry violation brought about the development of a comprehensive framework, known as the gravitational standard-model extension (SME), for studying deviations from exact Lorentz and CPT symmetry in nature. The development of this framework and its motivation led to an explosion of new tests of Lorentz symmetry over the past decade and to considerable theoretical interest in the subject. This work reviews the key concepts associated with Lorentz and CPT symmetry, the structure of the SME framework, and some recent experimental and theoretical results.

Superluminal neutrinos at OPERA confront pion decay kinematics

Violation of Lorentz invariance (VLI) has been suggested as an explanation of the superluminal velocities of muon neutrinos reported by OPERA. In this Letter, we show that the amount of VLI required to explain this result poses severe difficulties with the kinematics of the pion decay, extending its lifetime and reducing the momentum carried away by the neutrinos. We show that the OPERA experiment limits α=(ν(ν)-c)/c<4×10(-6). We then take recourse to cosmic-ray data on the spectrum of muons and neutrinos generated in Earth's atmosphere to provide a stronger bound on VLI: (ν-c)/c<10(-12).