Phase-transition from fractality to homogeneity in a large-scale universe

1996 ◽  
Vol 222 (6) ◽  
pp. 375-377 ◽  
Author(s):  
A. Bershadskii
2017 ◽  
Vol 32 (18) ◽  
pp. 1750097 ◽  
Author(s):  
M. Khurshudyan ◽  
R. Myrzakulov ◽  
As. Khurshudyan

The accelerated expansion of the large-scale universe can be explained in various ways. There are various modifications, and each of them makes an attempt to give its own explanation of the physics behind it. It is well known that modern cosmology is full of various phenomenological assumptions to obtain comprehensive results comparable with observational data. General Relativity is the main theory of gravity and proposed modifications compared to it, giving a hope to find explanations of phenomenological assumptions. f(T) theory of gravity is one of the options. In this paper, we will consider a particular example of f(T) theory and study the effects of various interactions on a cosmological model. Phase space analysis is used to have a qualitative understanding of the late-time behavior of the suggested cosmological models. During our study, we found that among phenomenological models suggested in this paper, we have cosmological models being in good agreement with the observational data. Moreover, study of the behavior of the deceleration parameter q showed a phase transition from a decelerated expanding universe to the accelerated (recent) expanding universe. On the other hand, for the parameters of the models giving the mentioned phase transition, we have estimated the present day values of statefinder parameters (r, s).


Universe ◽  
2020 ◽  
Vol 6 (10) ◽  
pp. 168
Author(s):  
Christopher Marsden ◽  
Francesco Shankar

In this work we present “Astera’’, a cosmological visualization tool that renders a mock universe in real time using Unreal Engine 4. The large scale structure of the cosmic web is hard to visualize in two dimensions, and a 3D real time projection of this distribution allows for an unprecedented view of the large scale universe, with visually accurate galaxies placed in a dynamic 3D world. The underlying data are based on empirical relations assigned using results from N-Body dark matter simulations, and are matched to galaxies with similar morphologies and sizes, images of which are extracted from the Sloan Digital Sky Survey. Within Unreal Engine 4, galaxy images are transformed into textures and dynamic materials (with appropriate transparency) that are applied to static mesh objects with appropriate sizes and locations. To ensure excellent performance, these static meshes are “instanced’’ to utilize the full capabilities of a graphics processing unit. Additional components include a dynamic system for representing accelerated-time active galactic nuclei. The end result is a visually realistic large scale universe that can be explored by a user in real time, with accurate large scale structure. Astera is not yet ready for public release, but we are exploring options to make different versions of the code available for both research and outreach applications.


2019 ◽  
Vol 34 (Supplement_1) ◽  
pp. i46-i57
Author(s):  
Robert Crease ◽  
Elyse Graham ◽  
Jamie Folsom

Abstract Over the past few years, research carried out at large-scale materials science facilities in the USA and elsewhere has undergone a phase transition that affected its character and culture. Research cultures at these facilities now resemble ecosystems, comprising of complex and evolving interactions between individuals, institutions, and the overall research environment. The outcome of this phase transition, which has been gradual and building since the 1980s, is known as the New (or Ecologic) Big Science [Crease, R. and Westfall, C. (2016). The new big science. Physics Today, 69: 30–6]. In this article, we describe this phase transition, review the practical challenges that it poses for historians, review some potential digital tools that might respond to these challenges, and then assess the theoretical implications posed by “database history’.


2019 ◽  
Vol 122 (21) ◽  
Author(s):  
Moritz Linkmann ◽  
Guido Boffetta ◽  
M. Cristina Marchetti ◽  
Bruno Eckhardt

2007 ◽  
Vol 363 (1-2) ◽  
pp. 121-124 ◽  
Author(s):  
V.G. Gurzadyan ◽  
C.L. Bianco ◽  
A.L. Kashin ◽  
H. Kuloghlian ◽  
G. Yegorian

2020 ◽  
Author(s):  
Klaus Regenauer-Lieb ◽  
Christoph Schrank ◽  
Oliver Gaede ◽  
Benjamin Marks ◽  
Manman Hu ◽  
...  

<p>We present the hypothesis that material instabilities based on multiscale and multiphysics dissipative waves hold the key for understanding the universality of physical phenomena that can be observed over many orders of scale. The approach is based on an extended version of the thermodynamic theory with internal variables (see related abstract by Antoine Jacquey et al. for session EMRP1.4 entitled: “Multiphysics of transient deformation processes leading to macroscopic instabilities in geomaterials”). The internal variables can, in many cases, shown to be related to order parameters in Lev Landau’s phase-transition theory. The extension presented in this contribution consists of replacing the jump condition for the symmetry-breaking order parameter at the critical point (e.g., density difference at the liquid-gas transition) through considering a second-order phase transition, where the internal variables change continuously from the critical point due to the propagation of material-damaging dissipative waves. This extension to the first-order theory allows assessing the dynamics of coupling the rates of chemical reactions, failure and fluid-flow as well as thermo-mechanical instabilities of materials. The approach gives physics-based insights into the processes that are commonly described by empirical relationships. Here, we present a first analytical model extended by numerical analyses and laboratory and field observations that show the existence of these precursor phenomena to large-scale instabilities. In the event that the propagating waves lead to a large-scale instability, the dissipation processes are predicted to leave tell-tale multi-scale structures in their wake, which can be used to decipher the dynamic processes underpinning the event.</p><p>First analyses from a laboratory analogue experiment are presented, illustrating the slow speed of the waves and their peculiar dispersion relationships and reflection from boundaries. An idealized 1-D (oedometric) compaction experiment of a highly porous (45% porosity) carbonate rock investigates the emergence of localized compaction bands proposed to be formed by long-term resonant collision of the transient dissipation waves. Complementary numerical models of the phenomenon allow in-depth analysis of the dynamics and illustrate the physics of the formation of dissipative waves.</p><p>For field application, we propose that a multiscale analysis - from the grain- over the outcrop- up to the lithospheric scale - can be used to extract quantitative information directly from natural deformation bands, fractures, and fault zones on, for example, the state of stress, the size of the underlying earthquakes, the flow and mechanical properties of the host rock, and the spatiotemporal evolution of fluid and mechanical pressure associated with faulting. The experimental investigation of the fundamental instability has broader applications in the fields of industrial processing of multiphase materials, civil, mechanical, and reservoir engineering and solid mechanics.</p>


Nanomaterials ◽  
2019 ◽  
Vol 9 (6) ◽  
pp. 834 ◽  
Author(s):  
Xu Chen ◽  
Mingfei Wu ◽  
Xingxing Liu ◽  
Ding Wang ◽  
Feng Liu ◽  
...  

A new simple way for tuning the phase transition temperature (PTT) of VO2 thin films has been proposed to solve the problem of changing the doping ratio by using the dual-target co-sputtering method. A series of samples with W doping ratios of 0%, 0.5%, 1%, 1.5% and 2% have been fabricated by sputtering V films with the power of pure and 2% W-doped V targets from 500 W: 0 W, 500 W: 250 W, 500 W: 500 W, 250 W: 500 W to 0 W: 500 W respectively and then annealed in an oxygen atmosphere to form VO2. The XRD results of both pure and W-doped VO2 samples reveal that VO2 forms and is the main component after annealing. The PTT can be tuned by controlling the sputtering power ratio of the pure and doped targets. It can be tuned easily from 64.3 °C to 36.5 °C by using the pure and 2% W-doped targets for demonstration, with W doping ratios from 0% to 2%. It is also valid for other doping elements and is a promising approach for the large-scale production of sputtering.


Sign in / Sign up

Export Citation Format

Share Document