Modifying the theory of gravity by changing independent variables

We study some particular modifications of gravity in search for a natural way to unify the gravitational and electromagnetic interaction. The certain components of connection in the appearing variants of the theory can be identified with electromagnetic potential. The methods of adding matter in the form of scalar and spinor fields are studied. In particular, the expansion of the local symmetry group up to $GL(2,C)$ is explored, in which equations of Einstein, Maxwell and Dirac are reproduced for the theory with Weyl spinor.Comment: LaTeX, 6 pages, based on a talk given at the XXth International Seminar on High Energy Physics (QUARKS-2018), Valday, Russia, May 27 - June 2, 201

Modifications of gravity via differential transformations of field variables

We discuss field theories appearing as a result of applying field transformations with derivatives (differential field transformations, DFT) to a known theory. We begin with some simple examples of DFTs to see the basic properties of the procedure. In this process the dynamics of the theory might either change or conserve. After that we concentrate on the theories of gravity which appear as a result of various DFT applied to general relativity, namely the mimetic gravity and Regge-Teitelboim embedding theory. We review main results related to the extension of dynamics in these theories, as well as the possibility to write down the action of a theory after DFT as the action of the original theory before DFT plus an additional term. Such a term usually contains some constraints with Lagrange multipliers and can be interpreted as an action of additional matter, which might be of use in cosmological applications, e.g. for the explanation of the effects of dark matter.Comment: 18 page

Description of gravity in the model with independent nonsymmetric connection

A generalization of General Relativity is studied. The standard Einstein-Hilbert action is considered in the Palatini formalism, where the connection and the metric are independent variables, and the connection is not symmetric. As a result of variation with respect to the metric Einstein equations are obtained. A variation with respect to the connection leads to an arbitrariness in the determination of connection, i.e. the presence of gauge invariance. Then a matter in a form of point particle which interacts with field of connection is introduced. Also the action is complemented by a kinetic term for field of the connection to avoid incompatible equation of motion. Thus after the variation procedures we obtain the Einstein equations, the geodesic equation and the Maxwell`s equations for electromagnetism, where some components of the connection play the role of the electromagnetic potential. Thereby the electromagnetic potential is obtained from the geometry of space-time.Comment: LaTeX, 6 pages, based on a talk given at the 13th International Workshop High Energy Physics and Quantum Field Theory, Yaroslavl, Russia, June 26 - July 3, 201

Волновые процессы в дрейфующем льду Cеверного Ледовитого океана в экспедиции MOSAiC. Зимний период

One of the main directions of theoretical and applied research in the Arctic is the study of physical and mechanical processes in the atmosphere — ice — ocean system. For this purpose, theoretical and experimental problems are solved. The paper employs the method of monitoring the state of drifting ice by means of autonomous seismic stations in the MOSAiC international expedition in 2019–2020. The method of remote registration of ice information with a discreteness of 100 Hz made it possible to obtain data on the processes of compression and crushing of ice of various temporal and spatial scales. The paper presents early findings on the development of physico-mechanical processes in the ice cover under the influence of wind, oceanic gravitational waves, compression and crushing phenomena during large-scale deformations in drifting ice. The amplitude-frequency spectra of surface gravitational waves obtained in this work provide sufficient reason for attributing the phenomena described to swell waves and infra-gravity waves that occur in the stormy areas of the oceans. New data have been obtained on low-frequency horizontally polarized waves caused by the compression of ice and movements along breaks in the cohesive ice cover. The article considers the possibilities of using instrumental monitoring of the occurrence and development of tidal compression and crushing in the drifting ice of the Arctic Ocean. The results obtained can be used to develop methods for predicting the state of ice in real time both in engineering tasks and for improving weather and climate forecasting models.Одной из основных научных и прикладных проблем в Арктике являются исследования физико-механических процессов в системе атмосфера — лед — океан. С этой целью решаются теоретические и экспериментальные задачи. В настоящей работе использовался метод мониторинга состояния дрейфующего льда с помощью автономных сейсмических станций в международной экспедиции MOSAiC в 2019–2020 гг. Метод дистанционной регистрации ледовой информации с дискретностью100 Гц позволил получить данные о процессах сжатия и торошения льдов различного временного и пространственного масштаба. В работе представлены первые результаты о развитии физико-механических процессов в ледяном покрове при воздействии ветра, океанических гравитационных волн, явлениях сжатия и торошения при крупномасштабных деформациях в дрейфующем льду. Полученные в работе амплитудно-частотные спектры поверхностных гравитационных волн являются основанием относить описанные явления к волнам зыби и инфрагравитационным волнам, возникающим в штормовых районах океанов. Получены новые данные о низкочастотных горизонтально-поляризованных волнах, обусловленных сжатием льдов и подвижками по разрывам в сплоченном ледяном покрове. Рассмотрены возможности использования инструментального мониторинга возникновения и развития приливного сжатия и торошения в дрейфующих льдах Северного Ледовитого океана. Полученные результаты могут быть использованы для разработки методов прогнозирования состояния льдов в режиме реального времени как в инженерных задачах, так и для совершенствования моделей прогноза погоды и климата