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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.


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TL;DR: In this article, the stability of the solutions and the bouncing and ΛCDM models using the Noether symmetries of f(R, T) theories has been investigated.
Abstract: Extended f(R) theories of gravity have been investigated from the symmetry point of view. We briefly has been investigated Noether symmetry of two types of extended f(R) theories: f(R, T) theory, in which curvature is coupled non-minimally to the trace of energy–momentum tensor Tμν and mimetic f(R) gravity, a theory with a scalar field degree of freedom, but ghost-free and with internal conformal symmetry. In both cases we write point-like Lagrangian for flat Friedmann–Lemaitre–Robertson–Walker (FLRW) cosmological background in the presence of ordinary matter. We have been shown that some classes of models existed with Noether symmetry in these viable extensions of f(R) gravity. As a motivated idea, we have been investigating the stability of the solutions and the bouncing and ΛCDM models using the Noether symmetries. We have been shown that in mimetic f(R) gravity bouncing and ΛCDM solutions are possible. Also a class of solutions with future singularities has been investigated.

121 citations

Journal ArticleDOI
TL;DR: The decay from the 23+ state at about 2-MeV excitation in the nuclei Ba140, Ce142, and Nd144, with 84 neutrons, was shown to be consistent with its identification as the lowest state of mixed symmetry in the U(5) limit of the neutron-proton version of the interacting-boson model as mentioned in this paper.
Abstract: The decay from the 23+ state at about 2-MeV excitation in the nuclei Ba140, Ce142, and Nd144, with 84 neutrons, is shown to be consistent with its identification as the lowest state of mixed symmetry in the U(5) limit of the neutron-proton version of the interacting-boson model.

121 citations

Journal ArticleDOI
TL;DR: In this article, the stiffness tensor relating the stress and strain in the generalized Hooke's law can take various forms depending upon the symmetry of the mechanical properties of the granular material.
Abstract: The stiffness tensor relating the stress and strain in the generalized Hooke's law can take various forms depending upon the symmetry of the mechanical properties of the granular material. This material symmetry is expected to be closely related to the packing structure of the granular material. In this paper, the microstructural continuum method is employed to study the relationship between the symmetry of mechanical properties and the packing structure for random granular packings. The distribution density functions characterizing the packing structure are represented by spherical harmonics expansion. Closed‐form solutions for the stiffness tensor are derived for anisotropic granular packings of equal spheres with linear interparticle contact interactions. The relation between the “fabric” parameters describing the density functions and the material symmetry are discussed. Bounds imposed by the condition of positive definiteness of strain energy on fabric parameters are also studied. Parametric study is...

121 citations

Journal ArticleDOI
TL;DR: Equilibrium configurations of the order-parameter tensor field in a Landau-de Gennes free energy are numerically modeled using a finite-element package and it is confirmed that the transition from the hedgehog to the ring structure is first order.
Abstract: We investigate the structure of defects in nematic liquid crystals confined in spherical droplets and subject to radial strong anchoring. Equilibrium configurations of the order-parameter tensor field in a Landau--de Gennes free energy are numerically modeled using a finite-element package. Within the class of axially symmetric fields, we find three distinct solutions: the familiar radial hedgehog, the small ring (or loop) disclination predicted by Penzenstadler and Trebin, and a solution that consists of a short disclination line segment along the rotational symmetry axis terminating in isotropic end points. Phase and bifurcation diagrams are constructed to illustrate how the three competing configurations are related. They confirm that the transition from the hedgehog to the ring structure is first order. The third configuration is metastable (in our symmetry class) and forms an alternate solution branch bifurcating off the radial hedgehog branch at the temperature below which the hedgehog ceases to be metastable. Dependence on temperature, droplet size, and elastic constants is investigated, and comparisons with other studies are made.

121 citations

Journal ArticleDOI
TL;DR: It is shown that the selection rule can be imposed by the rotational symmetry of metacrystals embedded into an isotropic organic nonlinear thin film, which may open new avenues for designing symmetry-dependent nonlinear optical responses with tailored plasmonic nanostructures.
Abstract: Nonlinear processes are often governed by selection rules imposed by the symmetries of the molecular configurations. The most well-known examples include the role of centrosymmetry breaking for the generation of even harmonics, and the selection rule related to the rotational symmetry in harmonic generation for fundamental beams with circular polarizations. While the role of centrosymmetry breaking in second harmonic generation has been extensively studied in plasmonic systems, the investigation of selection rules pertaining to circular polarization states of harmonic generation is limited to crystals, i.e., symmetries at the atomic level. In this Letter we demonstrate the rotational symmetry dependent third harmonic generation from nonlinear plasmonic metacrystals. We show that the selection rule can be imposed by the rotational symmetry of metacrystals embedded into an isotropic organic nonlinear thin film. The results presented here may open new avenues for designing symmetry-dependent nonlinear optical responses with tailored plasmonic nanostructures.

121 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202217
20211,679
20201,178
20191,006
20181,040
2017939