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The curvaton is a hypothetical elementary particle which mediates a scalar field in early universe cosmology. It can generate fluctuations during inflation, but does not itself drive inflation, instead it generates curvature perturbations at late times after the inflaton field has decayed and the decay products have redshifted away, when the curvaton is the dominant component of the energy density. It is used to generate a flat spectrum of CMB perturbations in models of inflation where the potential is otherwise too steep or in alternatives to inflation like the pre-Big Bang scenario.

Elementary particle Quantum particle having no known substructure

In particle physics, an elementary particle or fundamental particle is a subatomic particle with no sub structure, thus not composed of other particles. Particles currently thought to be elementary include the fundamental fermions, which generally are "matter particles" and "antimatter particles", as well as the fundamental bosons, which generally are "force particles" that mediate interactions among fermions. A particle containing two or more elementary particles is a composite particle.

Scalar field Assignment of numbers to points in space

In mathematics and physics, a scalar field associates a scalar value to every point in a space – possibly physical space. The scalar may either be a (dimensionless) mathematical number or a physical quantity. In a physical context, scalar fields are required to be independent of the choice of reference frame, meaning that any two observers using the same units will agree on the value of the scalar field at the same absolute point in space regardless of their respective points of origin. Examples used in physics include the temperature distribution throughout space, the pressure distribution in a fluid, and spin-zero quantum fields, such as the Higgs field. These fields are the subject of scalar field theory.

Cosmology Universe events since the Big Bang 13.8 billion years ago

Cosmology is a branch of astronomy concerned with the studies of the origin and evolution of the universe, from the Big Bang to today and on into the future. It is the scientific study of the origin, evolution, and eventual fate of the universe. Physical cosmology is the scientific study of the universe's origin, its large-scale structures and dynamics, and its ultimate fate, as well as the laws of science that govern these areas.

The model was proposed almost simultaneously in 2001 by three independent groups: Kari Enqvist and Martin S. Sloth, [1] David Wands and David H. Lyth, [2] Takeo Moroi and Tomo Takahashi. [3]

Kari Enqvist Finnish professor and writer

Kari-Pekka Enqvist is a professor of cosmology in the Department of Physical Sciences at the University of Helsinki. Enqvist was awarded his PhD in theoretical physics in 1983.

David Wands is Professor of Cosmology at the Institute of Cosmology and Gravitation, in the University of Portsmouth.

Professor David Lyth is a researcher in particle cosmology at the University of Lancaster. He has published over 165 papers as well as two books on early universe cosmology and cosmological inflation.

See also

Hubbles law observation in physical cosmology

Hubble's law, also known as the Hubble–Lemaître law, is the observation in physical cosmology that:

  1. Objects observed in deep space—extragalactic space, 10 megaparsecs (Mpc) or more—are found to have a redshift, interpreted as a relative velocity away from Earth;
  2. This Doppler shift-measured velocity of various galaxies receding from the Earth is approximately proportional to their distance from the Earth for galaxies up to a few hundred megaparsecs away.
Big Bang The prevailing cosmological model for the observable universe

The Big Bang theory is the prevailing cosmological model for the observable universe from the earliest known periods through its subsequent large-scale evolution. The model describes how the universe expanded from a very high-density and high-temperature state, and offers a comprehensive explanation for a broad range of phenomena, including the abundance of light elements, the cosmic microwave background (CMB), large scale structure and Hubble's law. If the observed conditions are extrapolated backwards in time using the known laws of physics, the prediction is that just before a period of very high density there was a singularity which is typically associated with the Big Bang. Physicists are undecided whether this means the universe began from a singularity, or that current knowledge is insufficient to describe the universe at that time. Detailed measurements of the expansion rate of the universe place the Big Bang at around 13.8 billion years ago, which is thus considered the age of the universe. After its initial expansion, the universe cooled sufficiently to allow the formation of subatomic particles, and later simple atoms. Giant clouds of these primordial elements later coalesced through gravity, eventually forming early stars and galaxies, the descendants of which are visible today. Astronomers also observe the gravitational effects of dark matter surrounding galaxies. Though most of the mass in the universe seems to be in the form of dark matter, Big Bang theory and various observations seem to indicate that it is not made out of conventional baryonic matter but it is unclear exactly what it is made out of.

Cosmological constant constant representing stress-energy density of the vacuum in Einsteins equation

In cosmology, the cosmological constant is the energy density of space, or vacuum energy, that arises in Albert Einstein's field equations of general relativity. It is closely associated to the concepts of dark energy and quintessence.


  1. Enqvist & Sloth (2002). "Adiabatic CMB perturbations in pre-Big Bang string cosmology". Nuclear Physics B. 626 (1–2): 395–409. arXiv: hep-ph/0109214 . Bibcode:2002NuPhB.626..395E. doi:10.1016/S0550-3213(02)00043-3.
  2. Lyth & Wands (2002). "Generating the curvature perturbation without an inflaton". Physics Letters B. 524 (1–2): 5–14. arXiv: hep-ph/0110002 . Bibcode:2002PhLB..524....5L. doi:10.1016/S0370-2693(01)01366-1.
  3. Moroi & Takahashi (2001). "Effects of Cosmological Moduli Fields on Cosmic Microwave Background". Physics Letters B. 522 (3–4): 215–221. arXiv: hep-ph/0110096 . Bibcode:2001PhLB..522..215M. doi:10.1016/S0370-2693(01)01295-3.

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Inflation (cosmology) rapid expansion of the universe

In physical cosmology, cosmic inflation, cosmological inflation, or just inflation, is a theory of exponential expansion of space in the early universe. The inflationary epoch lasted from 10−36 seconds after the conjectured Big Bang singularity to some time between 10−33 and 10−32 seconds after the singularity. Following the inflationary period, the universe continues to expand, but at a less rapid rate.

Cosmic microwave background Universe events since the Big Bang 13.8 billion years ago

The cosmic microwave background, in Big Bang cosmology, is electromagnetic radiation as a remnant from an early stage of the universe, also known as "relic radiation". The CMB is faint cosmic background radiation filling all space. It is an important source of data on the early universe because it is the oldest electromagnetic radiation in the universe, dating to the epoch of recombination. With a traditional optical telescope, the space between stars and galaxies is completely dark. However, a sufficiently sensitive radio telescope shows a faint background noise, or glow, almost isotropic, that is not associated with any star, galaxy, or other object. This glow is strongest in the microwave region of the radio spectrum. The accidental discovery of the CMB in 1964 by American radio astronomers Arno Penzias and Robert Wilson was the culmination of work initiated in the 1940s, and earned the discoverers the 1978 Nobel Prize in Physics.

Brane cosmology several theories in particle physics and cosmology related to superstring theory and M-theory

Brane cosmology refers to several theories in particle physics and cosmology related to string theory, superstring theory and M-theory.

Nima Arkani-Hamed American physicist

Nima Arkani-Hamed is an American-Canadian theoretical physicist of Iranian descent, with interests in high-energy physics, quantum field theory, string theory, cosmology and collider physics. Arkani-Hamed is now on the faculty at the Institute for Advanced Study in Princeton, New Jersey, and director of The Center for Future High Energy Physics (CFHEP) in Beijing, China. He was formerly a professor at Harvard University and the University of California, Berkeley.

The inflaton field is a hypothetical scalar field that is theorized to drive cosmic inflation in the very early universe. The field, originally theorized by Alan Guth, provides a mechanism by which a period of rapid expansion from 10−35 to 10−34 seconds after the initial expansion can be generated, forming a universe consistent with observed spatial isotropy and homogeneity.

In physical cosmology, leptogenesis is the generic term for hypothetical physical processes that produced an asymmetry between leptons and antileptons in the very early universe, resulting in the present-day dominance of leptons over antileptons. In the currently accepted Standard Model, lepton number is conserved; it is not possible to create leptons directly without corresponding antileptons. Leptogenesis can therefore only take place in theories of physics beyond the Standard Model.

String cosmology

String cosmology is a relatively new field that tries to apply equations of string theory to solve the questions of early cosmology. A related area of study is brane cosmology.

Savas Dimopoulos is a particle physicist at Stanford University. He worked at CERN from 1994 to 1997. Dimopoulos is well known for his work on constructing theories beyond the Standard Model.

Eternal inflation is a hypothetical inflationary universe model, which is itself an outgrowth or extension of the Big Bang theory.

Trimaximal mixing refers to the highly symmetric, maximally CP-violating, fermion mixing configuration, characterised by a unitary matrix having all its elements equal in modulus ( , ) as may be written, e.g.:

Christopher T. Hill American physicist

Christopher T. Hill is an American theoretical physicist at the Fermi National Accelerator Laboratory who did undergraduate work in physics at M.I.T., and graduate work at Caltech. Hill's Ph.D. thesis, "Higgs Scalars and the Nonleptonic Weak Interactions" (1977) contains the first discussion of the two-Higgs-doublet model.

Diffusion damping

In modern cosmological theory, diffusion damping, also called photon diffusion damping, is a physical process which reduced density inequalities (anisotropies) in the early universe, making the universe itself and the cosmic microwave background radiation (CMB) more uniform. Around 300,000 years after the Big Bang, during the epoch of recombination, diffusing photons travelled from hot regions of space to cold ones, equalising the temperatures of these regions. This effect is responsible, along with baryon acoustic oscillations, the Doppler effect, and the effects of gravity on electromagnetic radiation, for the eventual formation of galaxies and galaxy clusters, these being the dominant large scale structures which are observed in the universe. It is a damping by diffusion, not of diffusion.

In mathematical physics, de Sitter invariant special relativity is the speculative idea that the fundamental symmetry group of spacetime is the indefinite orthogonal group SO(4,1), that of de Sitter space. In the standard theory of general relativity, de Sitter space is a highly symmetrical special vacuum solution, which requires a cosmological constant or the stress–energy of a constant scalar field to sustain.

Thomas Carlos Mehen is an American physicist. His research has consisted of primarily Quantum chromodynamics (QCD) and the application of effective field theory to problems in hadronic physics. He has also worked on effective field theory for non-relativistic particles whose short range interactions are characterized by a large scattering length, as well as novel field theories which arise from unusual limits of string theory.

Renata Kallosh theoretical physicist

Renata Elizaveta Kallosh, is a theoretical physicist. She is a Professor of Physics at Stanford University, working there on supergravity, string theory and inflationary cosmology.

p-adic quantum mechanics is a collection of related research efforts in quantum physics that replace real numbers with p-adic numbers. Historically, this research was inspired by the discovery that the Veneziano amplitude of the open bosonic string, which is calculated using an integral over the real numbers, can be generalized to the p-adic numbers. This observation initiated the study of p-adic string theory. Another approach considers particles in a p-adic potential well, with the goal of finding solutions with smoothly varying complex-valued wave functions. Alternatively, one can consider particles in p-adic potential wells and seek p-adic valued wave functions, in which case the problem of the probabilistic interpretation of the p-adic valued wave function arises. As there does not exist a suitable p-adic Schrödinger equation, path integrals are employed instead. Some one-dimensional systems have been studied by means of the path integral formulation, including the free particle, the particle in a constant field, and the harmonic oscillator.

Augusto Sagnotti Italian theoretical physicist

Augusto Sagnotti is an Italian theoretical physicist at Scuola Normale.

Starobinsky inflation is a modification of general relativity in order to explain cosmological inflation.

In particle physics, family symmetries or horizontal symmetries are various discrete, global, or local symmetries between quark-lepton families or generations. While being conceptually useful, these symmetries are not yet finally confirmed. Some potentially relevant option considered in the literature may be associated with the local chiral SU(3)F family symmetry introduced in 1980 and further developed.