Black Hole Shadows Constrain Extended Gravity Prokopov, V. A.; Alexeyev, S. O.; Zenin, O. I.
Journal of experimental and theoretical physics,
07/2022, Letnik:
135, Številka:
1
Journal Article
Recenzirano
Odprti dostop
The first images of black hole shadows open new possibilities to constrain modern extended gravity theories. We present the method of shadow background calculation for black hole solutions in the ...form of Taylor series where
g
11
= –
. The method is extended to general nonrotating case
g
11
≠ –
. The results of the analysis are compared with the predictions of General relativity taking into account the Event Horizon Telescope data. The results for the Horndesky model with the Gauss–Bonnet invariant, loop quantum gravity, Bumblebee model and Gauss–Bonnet gravity are in full agreement with the observations of M87*. In conformal gravity, large values of
m
2
and
Q
s
must be excluded. In STEGR
f
(
Q
) gravity the observational limits on the parameter α are: –0.025 < α < 0.04. For an alternative generalization of the Bumblebee model with the Schwarzschild approximation: –0.3 <
l
< 0.45. These results demonstrate the maximum one can achieve without taking into account of the rotation of a black hole.
When the paper V. Prokopov, S. Alexeyev, and O. Zenin, J. Exp. Theor. Phys.
135
, 91 (2022) was already published, the Event Horizon Telescope (EHT) obtained the first direct image of a black hole in ...the center of our galaxy, i.e. Sagittarius A* (see The Event Horizon Telescope Collab., Astrophys. J. Lett.
930
(L17) (2022)). Here we state that the results obtained earlier in the paper V. Prokopov, S. Alexeyev, and O. Zenin, J. Exp. Theor. Phys.
135
, 91 (2022) for the Horndesky model with the Gauss-Bonnet invariant, loop quantum gravity, scalar bumblebee model, Gauss–Bonnet gravity and conformal gravity are in the agreement with Sgr A* observations. The new observational data limit the values of the parameter α in
f
(
Q
) gravity: –0.025 < α < 0.005. For the alternative generalization of the bumblebee metric with the Schwarzschild approximation, the constraint transfers to –0.05 <
l
< 0.45. The obtained limits demonstrate the maximum that can be achieved without taking into account the black hole rotation.
Despite the fact that the methods of dynamic interphase tensiometry and rheology are used for the study of blood and other biological fluids, there is no single unified approach in the methodology of ...analysis and interpretation of the results in medicine. However, in some cases, the numerical characteristics obtained do not have a simple physical meaning and do not allow us to assess the real contribution of individual components and, as a result, it is impossible to identify the main link. Considering the divergence and lack of data on rheology, multicomponence, and uncertainty of composition, there have been practically no successful attempts to create the models that allow determining the contribution of individual blood components. The purpose of this work has been to create a model on the basis of which it would be possible to obtain information about the physical constants and parameters of individual components of plasma and/or blood serum for medical diagnostics. The study has been performed on the samples of two groups of people: (1) 15 patients with ischemic heart disease aged 51 to 76 years; (2) 15 conditionally healthy volunteers aged 50 to 75 years. The method of “salting out” proteins has been used for fractionation of serum/plasma in order to obtain a fraction of low-molecular metabolites. Further determination of interphase tensiometry has been carried out by the hanging drop method using the PAT-1 hardware and software complex (Sinterface Technologies, Germany). Using the obtained data of dynamic surface tension and the proposed mathematical model, it can be concluded that: (1) the tensiometric characteristics of the blood serum of the subjects from group 1 and 2 differ in terms of the dynamic and equilibrium surface tension; (2) the quantitative and qualitative contribution of the coagulation system to the surface tension and the sum of the low-molecular-weight compound concentrations have been calculated; (3) the contribution of low-molecular-weight metabolites in the formation of the plasma and serum surface tension has been evaluated; and (4) the heterogeneity of the qualitative composition of the fractions of low-molecular-weight substances in the studied groups has been shown.
Pendant drop and bubble shape methods are employed to study the tensiometric and rheological parameters of blood serum and plasma in 45 patients 49–70 years old subjected to surgical operations under ...the conditions of artificial circulation because of ischemic heart disease (first group) and heart valve pathology (second group). Blood sampling is performed 1 h before and 12 h after (the first day) the operation, as well as on the 7th postoperative day. Statistically significant changes in the surface tension and viscoelasticity modulus are observed on the 1st day after the operation in both groups, thereby indicating a substantial increase in the content of surfactants in the blood serum. On the seventh day of the postoperative period, a positive dynamics is observed; however, the studied rheological parameters—in particular, viscoelasticity modulus
E
—at frequencies of 0.1 and 0.01 Hz statistically reliably exceed their preoperative level and do not reach the values characteristic of healthy people. Thus, the pathological deviations of biochemical parameters (contents of glucose, urea, creatinine, albumin, and lipoproteins) that affect blood viscosity are accompanied by substantial changes in the surface tension and dilatational viscoelasticity of blood serum. However, the examined biochemical markers are not dominating predictors for changes in the rheological and tensiometric properties of blood.
In screw volumetric machines, cycloidal screw surfaces of complex profile are used as working bodies. This paper is devoted to study of the technological possibilities of preparing the production of ...such screw surfaces using a special processing strategy with a nonprofiled tool on a 4-axis CNC machine. During this study, a special analytical criterion was proposed to evaluate the possibility of processing screw surfaces with various parameters. A computer experiment was performed to confirm the performance of the proposed criterion, as well as a series of full-scale experiments.
Review of Particle Physics Tanabashi, M.; Nakamura, K.; Tanaka, J. ...
Physical review. D,
08/2018, Letnik:
98, Številka:
3
Journal Article
Recenzirano
Odprti dostop
The Review summarizes much of particle physics and cosmology. Using data from previous editions, plus 2,873 new measurements from 758 papers, we list, evaluate, and average measured properties of ...gauge bosons and the recently discovered Higgs boson, leptons, quarks, mesons, and baryons. We summarize searches for hypothetical particles such as supersymmetric particles, heavy bosons, axions, dark photons, etc. Particle properties and search limits are listed in Summary Tables. We give numerous tables, figures, formulae, and reviews of topics such as Higgs Boson Physics, Supersymmetry, Grand Unified Theories, Neutrino Mixing, Dark Energy, Dark Matter, Cosmology, Particle Detectors, Colliders, Probability and Statistics. Among the 118 reviews are many that are new or heavily revised, including a new review on Neutrinos in Cosmology.
Review of Particle Physics Workman, R L; Klempt, E; Agashe, K ...
Progress of theoretical and experimental physics,
08/2022, Letnik:
2022, Številka:
8
Journal Article
Recenzirano
Odprti dostop
Abstract
The Review summarizes much of particle physics and cosmology. Using data from previous editions, plus 2,143 new measurements from 709 papers, we list, evaluate, and average measured ...properties of gauge bosons and the recently discovered Higgs boson, leptons, quarks, mesons, and baryons. We summarize searches for hypothetical particles such as supersymmetric particles, heavy bosons, axions, dark photons, etc. Particle properties and search limits are listed in Summary Tables. We give numerous tables, figures, formulae, and reviews of topics such as Higgs Boson Physics, Supersymmetry, Grand Unified Theories, Neutrino Mixing, Dark Energy, Dark Matter, Cosmology, Particle Detectors, Colliders, Probability and Statistics. Among the 120 reviews are many that are new or heavily revised, including a new review on Machine Learning, and one on Spectroscopy of Light Meson Resonances.
The Review is divided into two volumes. Volume 1 includes the Summary Tables and 97 review articles. Volume 2 consists of the Particle Listings and contains also 23 reviews that address specific aspects of the data presented in the Listings.
The complete Review (both volumes) is published online on the website of the Particle Data Group (pdg.lbl.gov) and in a journal. Volume 1 is available in print as the PDG Book. A Particle Physics Booklet with the Summary Tables and essential tables, figures, and equations from selected review articles is available in print, as a web version optimized for use on phones, and as an Android app.
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