Open Access. Powered by Scholars. Published by Universities.®
Physical Sciences and Mathematics Commons™
Open Access. Powered by Scholars. Published by Universities.®
Articles 1 - 12 of 12
Full-Text Articles in Physical Sciences and Mathematics
Lorentz- And C P T -Violating Standard Model Extension In Chiral Perturbation Theory, Brett Altschul, Matthias R. Schindler
Lorentz- And C P T -Violating Standard Model Extension In Chiral Perturbation Theory, Brett Altschul, Matthias R. Schindler
Faculty Publications
Lorentz and CPT violation in hadronic physics must be tied to symmetry violations at the underlying quark and gluon level. Chiral perturbation theory provides a method for translating novel operators that may appear in the Lagrange density for color-charged parton fields into equivalent forms for effective theories at the meson and baryon levels. We extend the application of this technique to the study of Lorentzviolating and potentially CPT-violating operators from the minimal standard model extension. For dimension-4 operators, there are nontrivial relations between the coefficients of baryon-level operators related to underlying quark and gluon operators with the same Lorentz structures. …
Bounds On Vacuum-Orthogonal Lorentz And Cpt Violation From Radiative Corrections, Brett David Altschul
Bounds On Vacuum-Orthogonal Lorentz And Cpt Violation From Radiative Corrections, Brett David Altschul
Faculty Publications
Certain forms of Lorentz violation in the photon sector are difficult to bound directly, since they are “vacuum orthogonal”—meaning they do not change the solutions of the equations of motion in vacuum. However, these very same terms have a unique tendency to contribute large radiative corrections to effects in other sectors. Making use of this, we set bounds on four previously unconstrained d=5 photon operators at the 10−25–10−31 GeV−1 levels.
Hadronic Lorentz Violation In Chiral Perturbation Theory Including The Coupling To External Fields, Rasha Kamand, Brett David Altschul, Matthias R. Schindler
Hadronic Lorentz Violation In Chiral Perturbation Theory Including The Coupling To External Fields, Rasha Kamand, Brett David Altschul, Matthias R. Schindler
Faculty Publications
If any violation of Lorentz symmetry exists in the hadron sector, its ultimate origins must lie at the quark level. We continue the analysis of how the theories at these two levels are connected, using chiral perturbation theory. Considering a 2-flavor quark theory, with dimension-4 operators that break Lorentz symmetry, we derive a low-energy theory of pions and nucleons that is invariant under local chiral transformations and includes the coupling to external fields. The pure meson and baryon sectors, as well as the couplings between them and the couplings to external electromagnetic and weak gauge fields, contain forms of Lorentz …
No Contact Terms For The Magnetic Field In Lorentz- And Cpt-Violating Electrodynamics, Karl Schober, Brett David Altschul
No Contact Terms For The Magnetic Field In Lorentz- And Cpt-Violating Electrodynamics, Karl Schober, Brett David Altschul
Faculty Publications
In a Lorentz- and CPT-violating modification of electrodynamics, the fields of a moving charge are known to have unusual singularities. This raises the question of whether the singular behavior may include δ-function contact terms, similar to those that appear in the fields of idealized dipoles. However, by calculating the magnetic field of an infinite straight wire in this theory, we demonstrate that there are no such contact terms in the magnetic field of a moving point charge.
Lorentz Violation In Fermion-Antifermion Decays Of Spinless Particles, Brett David Altschul
Lorentz Violation In Fermion-Antifermion Decays Of Spinless Particles, Brett David Altschul
Faculty Publications
If Lorentz and CPT violation exist, they could affect the decays of scalar and pseudoscalar particles. For a decay into a fermion and an antifermion (not necessarily of the same mass), both the total decay rate and the outgoing particle distribution may be modified, through interference between the conventional decay mechanism and a separate Lorentz-violating mechanism. The modifications are sensitive to forms of Lorentz violation that are otherwise rather difficult to study, since at tree level they do not affect particle propagation, but only interaction vertices. Using existing experimental data on charged pion decay, it is possible to constrain three …
Lorentz And Cpt Violation In Scalar-Mediated Potentials, Brett David Altschul
Lorentz And Cpt Violation In Scalar-Mediated Potentials, Brett David Altschul
Faculty Publications
In Lorentz- and CPT-violating effective field theories involving scalar and spinor fields, there exist forms of Lorentz violation that modify only the scalar-spinor Yukawa interaction vertices. These affect low-energy fermion and antifermion scattering processes through modifications to the nonrelativistic Yukawa potentials. The modified potentials involve novel combinations of momentum, spin, and Lorentz-violating background tensors.
Neutrino Beam Constraints On Flavor-Diagonal Lorentz Violation, Brett David Altschul
Neutrino Beam Constraints On Flavor-Diagonal Lorentz Violation, Brett David Altschul
Faculty Publications
Breaking of isotropy and Lorentz boost invariance in the dynamics of second-generation leptons would lead to direction-dependent changes in the lifetimes of charged pions. This would make the intensity of a neutrino beam produced via pion decay a function of the beam orientation. The experimental signature of this phenomenon—sidereal variations in the event rate at a downstream neutrino detector—has already been studied, in searches for Lorentz-violating neutrino oscillations. Existing analyses of MINOS near detector data can be used to constrain the flavor-diagonal Lorentz violation coefficients affecting muon neutrino speeds at roughly the 10−5 level.
Coupling Right- And Left-Handed Photons Differently To Charged Matter, Brett David Altschul
Coupling Right- And Left-Handed Photons Differently To Charged Matter, Brett David Altschul
Faculty Publications
We consider a modification of electrodynamics in which right- and left-circularly polarized photons are coupled to charged sources differently. Even though photon helicity is a Lorentz invariant quantity, such a modification breaks Lorentz symmetry, as well as locality. The modified theory includes novel magnetic forces between perpendicular currents. Existing data can be used to constrain the modification at approximately a 2 x 10^(-3) level.
Consequences Of Neutrino Lorentz Violation For Leptonic Meson Decays, Brett David Altschul
Consequences Of Neutrino Lorentz Violation For Leptonic Meson Decays, Brett David Altschul
Faculty Publications
If the observation by OPERA of apparently superluminal neutrinos is correct, the Lagrangian for second-generation leptons must break Lorentz invariance. We calculate the effects of an energy-independent change in the neutrino speed on another observable, the charged pion decay rate. The rate decreases by an factor [1 - 3/(1 - (m_mu)^2 / (m_pi) ^ 2) (< v_(nu) > - 1)], where < v_(nu) > is the (directionally averaged) neutrino speed in the pion's rest frame. This provides a completely independent experimental observable that is sensitive to the same forms of Lorentz violation as a neutrino time of flight measurement.
Modeling-Free Bounds On Nonrenormalizable Isotropic Lorentz And Cpt Violation In Qed, Brett David Altschul
Modeling-Free Bounds On Nonrenormalizable Isotropic Lorentz And Cpt Violation In Qed, Brett David Altschul
Faculty Publications
The strongest bounds on some forms of Lorentz and CPT violation come from astrophysical data, and placing such bounds may require understanding and modeling distant sources of radiation. However, it is also desirable to have bounds that do not rely on these kinds of detailed models. Bounds that do not rely on any modeling of astrophysical objects may be derived both from laboratory experiments and certain kinds of astrophysical observations. The strongest such bounds on isotropic modifications of electron, positron, and photon dispersion relations of the form E^2 = p^2 + m^ 2 + epsilon p^3 come from data on …
Lorentz Violation With An Antisymmetric Tensor, Brett David Altschul, Quentin G. Bailey, Alan Kostelecky
Lorentz Violation With An Antisymmetric Tensor, Brett David Altschul, Quentin G. Bailey, Alan Kostelecky
Faculty Publications
Field theories with spontaneous Lorentz violation involving an antisymmetric 2-tensor are studied. A general action including nonminimal gravitational couplings is constructed, and features of the Nambu-Goldstone and massive modes are discussed. Minimal models in Minkowski spacetime exhibit dualities with Lorentz-violating vector and scalar theories. The post-Newtonian expansion for nonminimal models in Riemann spacetime involves qualitatively new features, including the absence of an isotropic limit. Certain interactions producing stable Lorentz-violating theories in Minkowski spacetime solve the renormalization-group equations in the tadpole approximation.
Disentangling Forms Of Lorentz Violation With Complementary Clock Comparison Experiments, Brett David Altschul
Disentangling Forms Of Lorentz Violation With Complementary Clock Comparison Experiments, Brett David Altschul
Faculty Publications
Atomic clock comparisons provide some of the most precise tests of Lorentz and CPT symmetries in the laboratory. With data from multiple such experiments using different nuclei, it is possible to constrain new regions of the parameter space for Lorentz violation. Relativistic effects in the nuclei allow us to disentangle forms of Lorentz violation which could not be separately measured in purely nonrelativistic experiments. The disentangled bounds in the neutron sectors are at the 10−28 GeV level, far better than could be obtained with any other current technique.