Symmetry (physics)

About: Symmetry (physics) is a research topic. Over the lifetime, 26435 publications have been published within this topic receiving 500189 citations. The topic is also known as: symmetry (physics) & physical symmetry.

Clouds of strings in general relativity

Abstract: A gauge-invariant version of the Stachel string cloud model is presented. Some formal aspects as well as the energy conditions for the model are studied. The general solution to Einstein's equations for a cloud of strings with spherical, plane, and a particular case of cylindrical symmetry are studied. The solution with spherical symmetry is used to construct a double-layer model of a star.

Dual electromagnetism: Helicity, spin, momentum, and angular momentum

Abstract: The dual symmetry between electric and magnetic fields is an important intrinsic property of Maxwell equations in free space. This symmetry underlies the conservation of optical helicity and, as we show here, is closely related to the separation of spin and orbital degrees of freedom of light (the helicity flux coincides with the spin angular momentum). However, in the standard field-theory formulation of electromagnetism, the field Lagrangian is not dual symmetric. This leads to problematic dual-asymmetric forms of the canonical energy–momentum, spin and orbital angular-momentum tensors. Moreover, we show that the components of these tensors conflict with the helicity and energy conservation laws. To resolve this discrepancy between the symmetries of the Lagrangian and Maxwell equations, we put forward a dual-symmetric Lagrangian formulation of classical electromagnetism. This dual electromagnetism preserves the form of Maxwell equations, yields meaningful canonical energy–momentum and angular-momentum tensors, and ensures a self-consistent separation of the spin and orbital degrees of freedom. This provides a rigorous derivation of the results suggested in other recent approaches. We make the Noether analysis of the dual symmetry and all the Poincare symmetries, examine both local and integral conserved quantities and show that only the dual electromagnetism naturally produces a complete self-consistent set of conservation laws. We also discuss the observability of physical quantities distinguishing the standard and dual theories, as well as relations to quantum weak measurements and various optical experiments.

Weakly interacting massive particle-nucleus elastic scattering response

Abstract: A model independent formulation of WIMP-nucleon scattering was recently developed in Galileaninvariant effective field theory and embedded in the nucleus, determining the most general WIMP-nucleus elastic response. This formulation shows that the standard description of WIMP elastic scattering in terms spin-dependent and spin-independent responses frequently fails to identify the dominant operators governing the scattering, omitting four of the six responses allowed by basic symmetry considerations. Consequently comparisons made between experiments that are based on a spin-independent/spindependent analysis can be misleading for many candidate interactions, mischaracterizing the magnitude and multipolarity (e.g., scalar or vector) of the scattering. The new responses are associated with velocitydependent WIMP couplings and correspond to familiar electroweak nuclear operators such as the orbital angular momentum ~l(i) and the spin-orbit interaction ~σ(i) ·~l(i). Such operators have distinct selection rules and coherence properties, and thus open up new opportunities for using low-energy measurements to constrain ultraviolet theories of dark matter. The community’s reliance on simplified descriptions of WIMP-nucleus interactions reflects the absence of analysis tools that integrate general theories of dark matter with standard treatments of nuclear response functions. To bridge this gap, we have constructed a public-domain Mathematica package for WIMP analyses based on our effective theory formulation. Script inputs are 1) the coefficients of the effective theory, through which one can characterize the low-energy consequences of arbitrary ultraviolet theories of WIMP interactions; and 2) one-body density matrices for commonly used targets, the most compact description of the relevant nuclear physics. The generality of the effective theory expansion guarantees that the script will remain relevant as new ultraviolet theories are explored; the use of density matrices to factor the nuclear physics from the particle physics will allow nuclear structure theorists to update the script as new calculations become available, independent of specific particle-physics contexts. The Mathematica package outputs the resulting response functions (and associated form factors) and also the differential event rate, once a galactic WIMP velocity profile is specified, and thus in its present form provides a complete framework for experimental analysis. The Mathematica script requires no a priori knowledge of the details of the non-relativistic effective field theory or nuclear physics, though the core concepts are reviewed here and in [1].