AI Article Synopsis
Article Abstract
The Universe can be made flat and smooth by undergoing a phase of ultraslow (ekpyrotic) contraction, a condition achievable with a single, canonical scalar field and conventional general relativity. It has been argued, though, that generating scale-invariant density perturbations requires at least two scalar fields and a two-step process that first produces entropy fluctuations and then converts them to curvature perturbations. In this Letter we identify a loophole in the argument and introduce an ekpyrotic model based on a single, canonical scalar field that generates nearly scale-invariant curvature fluctuations through a purely "adiabatic mechanism" in which the background evolution is a dynamical attractor. The resulting spectrum can be slightly red with distinctive non-Gaussian fluctuations.
Download full-text PDF |
Source |
|---|---|
| http://dx.doi.org/10.1103/PhysRevLett.104.091301 | DOI Listing |
Publication Analysis
Top Keywords
Similar Publications
Vector modes are well-defined field distributions with spatially varying polarization states, rendering them irreducible to the product of a single spatial mode and a single polarization state. Traditionally, the spatial degree of freedom of vector modes is constructed using two orthogonal modes from the same family. Here, we introduce a novel class of vector modes whose spatial degree of freedom is encoded by combining modes from both the Hermite- and Laguerre-Gaussian families, ensuring that the modes are shape-invariant upon propagation.
View Article and Find Full Text PDFA scalar, harmonic beam-like field possessing an arbitrary number of orbital angular momentum (OAM) components is shown to trace an ellipse, termed here the orbitalization ellipse, at a given transverse cross section and radius, in the space spanned by the spiral OAM basis. The plane and the structure of the ellipse can be readily found by constructing its conjugate semi-diameter vectors from the OAM components.
View Article and Find Full Text PDFFree-space optical (FSO) communication has the advantages of large bandwidth and high security and being license-free, making it the preferred solution for addressing the "last kilometer" of information transmission. However, it is susceptible to fluctuations in the received optical power (ROP) due to atmospheric turbulence and pointing errors, resulting in the inevitable free-space optical communication transmission performance degradation. In this work, we experimentally verified the turbulence resistance of the cylindrical vector beam (CVB) over a 3 km long free-space field trial link.
View Article and Find Full Text PDFElectric Field-Induced Nonreciprocal Directional Dichroism in a Time-Reversal-Odd Antiferromagnet.
Adv Mater
January 2025
Department of Applied Physics, University of Tokyo, Bunkyo-ku, Tokyo, 113-8656, Japan.
Antiferromagnets with broken time-reversal ( ) symmetry ( -odd antiferromagnets) have gained extensive attention, mainly due to their ferromagnet-like behavior despite the absence of net magnetization. However, certain types of -odd antiferromagnets remain inaccessible by the typical ferromagnet-like phenomena (e.g.
View Article and Find Full Text PDFMagnetic field control over the axial character of Higgs modes in charge-density wave compounds.
Nat Commun
January 2025
Department of Physics and Astronomy, Seoul National University, Seoul, Korea.
Understanding how symmetry-breaking processes generate order out of disorder is among the most fundamental problems of nature. The scalar Higgs mode - a massive (quasi-) particle - is a key ingredient in these processes and emerges with the spontaneous breaking of a continuous symmetry. Its related exotic and elusive axial counterpart, a Boson with vector character, can be stabilized through the simultaneous breaking of multiple continuous symmetries.
View Article and Find Full Text PDFWant AI Summaries of new PubMed Abstracts delivered to your In-box?
Enter search terms and have AI summaries delivered each week - change queries or unsubscribe any time!