Results 51 to 60 of about 60,199 (278)

Evolution of perturbations in distinct classes of canonical scalar field models of dark energy

, 2010
Dark energy must cluster in order to be consistent with the equivalence principle. The background evolution can be effectively modelled by either a scalar field or by a barotropic fluid.The fluid model can be used to emulate perturbations in a scalar ...
B. Novosyadlyj, C. G. Lacey, H. K. Jassal, J. S. Bagla, K. A. Milton, T. Padmanabhan, V. Sahni, V. Sahni   +7 more
core   +1 more source

Scalar perturbations in cosmological f(R) models: the cosmic screening approach

European Physical Journal C: Particles and Fields, 2018
We investigate cosmological perturbations for nonlinear f(R) models within the cosmic screening approach. Matter is considered both in the form of a set of discrete point-like massive bodies and in the form of a continuous pressureless perfect fluid.
Özgür Akarsu, Ruslan Brilenkov, Maxim Eingorn, Valerii Shulga, Alexander Zhuk   +4 more
doaj   +1 more source

Generating cosmological perturbations in non-singular Horndeski cosmologies

Journal of High Energy Physics, 2023
We construct a concrete model of Horndeski bounce with strong gravity in the past. Within this model we show that the correct spectra of cosmological perturbations may be generated at early contracting epoch, with mild fine-tuning ensuring that the ...
Yulia Ageeva, Pavel Petrov, Valery Rubakov   +2 more
doaj   +1 more source

Cosmological perturbations in the inflationary Universe [PDF]

, 1997
Previously defined covariant and gauge-invariant perturbation variables, representing, e.g., the fractional spatial energy density gradient on hypersurfaces of constant expansion, are used to simplify the linear perturbation analysis of a classical ...
A. R. King, A. R. Liddle, D. H. Lyth, D. H. Lyth, D. Lyth, D. W. Olson, E. K. Kolb, E. M. Lifshitz, E. R. Harrison, G. Börner, G. Chibisov, G. F. R. Ellis, H. Kodama, J. A. Frieman, J. C. Jackson, J. Hwang, J. Hwang, J. Hwang, J. M. Bardeen, L. P. Grishchuk, M. Bruni, M. Bruni, M. S. Madsen, N. Deruelle, P. Ginsparg, P. K. S. Dunsby, R. R. Caldwell, S. K. Blau, S. W. Hawking, S. W. Hawking, V. F. Mukhanov, V. Lukash, Winfried Zimdahl   +32 more
core   +2 more sources

Transient Antiskyrmion‐Mediated Topological Transitions in Isotropic Magnets

Advanced Science, EarlyView.
A transient antiskyrmion‐mediated pathway that drives repeated stripe‐to‐skyrmion transitions is revealed, producing a net increase in topological charge in isotropic Dzyaloshinskii–Moriya interaction films. Experiments and simulations identify the antiskyrmion as a metastable excitation, enabling stochastic bitstream generation for probabilistic ...
Bingqian Dai, Tianyi Wang, Albert Lee, Shijie Xu, Zhongjian Bian, Xinyue Zhu, Puyang Huang, Aadi Chaturvedi, Yaochen Li, Yang Cheng, Qingyuan Shu, Haoran He, Hanshen Huang, Lixuan Tai, Kin Wong, Jinbo Yang, Anjan Soumyanarayanan, Zhaochu Luo, Kang L. Wang   +18 more
wiley   +1 more source

Appearances are deceptive: can graviton have a mass?

Journal of High Energy Physics
We study the dynamics of linear gravitational perturbations on cosmological backgrounds of massive fermionic fields. We observe that, when gravitational and matter action are expanded to quadratic order in gravitational perturbations on cosmological ...
Leihua Liu, Tomislav Prokopec
doaj   +1 more source

DENSITY PERTURBATIONS IN A REALISTIC UNIVERSE

Odessa Astronomical Publications, 2017
We analyze evolution of density perturbations in a flat or open universe filled in with matter, relativistic particles and possibly cosmological constant. Density perturbations grow very slowly in a universe filled in with low mass neutrinos.
M. Demianski, Z. Golda, A. Woszczyna
doaj   +1 more source

‘Turkeys Cannot Vote for Christmas’: Why Epistemic Disobedience in an Anti‐Black World Matters

Australian Journal of Social Issues, EarlyView.
ABSTRACT Never in the history of global coloniality has the idea of epistemic disobedience been as important as in the 21st century. This is not only because the struggle for decolonisation has shifted from physical confrontation between the coloniser and the colonised into a battle of ideas but also because the former has deployed the idea of ...
Morgan Ndlovu
wiley   +1 more source

PERTURBATIONS IN BOUNCING COSMOLOGICAL MODELS [PDF]

International Journal of Modern Physics D, 2004
I describe the features and general properties of bouncing models and the evolution of cosmological perturbations on such backgrounds. I will outline possible observational consequences of the existence of a bounce in the primordial Universe and I will make a comparison of these models with standard long inflationary scenarios.
openaire   +3 more sources

Universal Entanglement and an Information‐Complete Quantum Theory

Advanced Physics Research, EarlyView.
This Perspective summarize an informationcomplete quantum theory which describes a fully quantum world without any classical systems and concepts. Here spacetime/gravity, having to be a physical quantum system, universally entangles matter (matter fermions and their gauge fields) as an indivisible trinity, and encodes information‐complete physical ...
Zeng‐Bing Chen
wiley   +1 more source