Leptogenesis (physics)

Leptogenesis (physics)

In the strict sense, leptogenesis is a process which creates leptons. Theories of leptogenesis try to explain how the Universe changed from a state with no leptons just after the Big Bang to a state containing many leptons (mostly electrons) today.

The equivalent problem for baryons is called baryogenesis. While there are no observational bounds on the relative number of leptons and anti-leptons, since leptons can be converted to neutrinos or anti-neutrinos and remain invisible, there is observed a significant imbalance in the number of baryons and anti-baryons.

It should be understood however that it is not possible to create only electrons (or only protons) without violating the conservation of the electric charge. In other words, the conservation of the electric charge requires an equal number of electrons and protons.

Baryogenesis and leptogenesis are also connected by a phenomenon that happens in the currently accepted model for the elementary interactions, the Standard Model. Indeed, certain (non-perturbative) configurations of gauge fields that are called sphalerons can convert leptons into baryons and "vice versa". This means that the standard model is in principle able to provide a mechanism to create baryons and leptons, realizing a speculative possibility suggested by A. Sakharov in the sixties. The simplest version of the standard model, however, is quantitatively unable to realize this possibility.

A simple modification of the standard model that is instead able to realize the program of Sakharov is the one suggested by Fukugita and Yanagida. The standard model is augmented by adding right handed neutrinos, permitting implementation of the see-saw mechanism and providing the neutrinos with mass. At the same time, the augmented model is able to spontaneously generate leptons from the decays of right handed neutrinos. Finally, the sphalerons are able to convert the spontaneously generated lepton asymmetry into the observed baryonic asymmetry. Often, by an extension terms, the physicists use the word leptogenesis to denote the mechanism here described.

See also

*Baryogenesis


Wikimedia Foundation. 2010.

Игры ⚽ Поможем решить контрольную работу

Look at other dictionaries:

  • Physics beyond the Standard Model — Beyond the Standard Model Standard Model …   Wikipedia

  • Leptogenesis — *In physics, leptogenesis is the process of creating leptons in the early stages of the universe. *In biblical studies, leptogenesis is an alternative name for book of Jubilees …   Wikipedia

  • Electron — For other uses, see Electron (disambiguation). Electron Experiments with a Crookes tube first demonstrated the particle nature of electrons. In this illustration, the profile of the cross shaped target is projected against the tube face at right… …   Wikipedia

  • Neutrino oscillation — is a quantum mechanical phenomenon predicted by Bruno Pontecorvo[1] whereby a neutrino created with a specific lepton flavor (electron, muon or tau) can later be measured to have a different flavor. The probability of measuring a particular… …   Wikipedia

  • Baryogenesis — Unsolved problems in physics Why does the observable universe have more matter than antimatter? …   Wikipedia

  • Structure formation — refers to a fundamental problem in physical cosmology. The universe, as is now known from observations of the cosmic microwave background radiation, began in a hot, dense, nearly uniform state approximately 13.7 Gyr ago. [cite journal |author=D.… …   Wikipedia

  • Baryon — Baryons are the family of subatomic particles with a baryon number of 1. The term baryon is usually used to refer to triquarks baryons made of three quarks. Exotic baryons made of four quarks and one antiquark are known as the pentaquarks, but… …   Wikipedia

  • Wilfried Buchmüller — (* 1950) ist ein deutscher theoretischer Elementarteilchenphysiker. Buchmüller studierte Physik an der Universität Bonn und am Imperial College in London. 1977 promovierte er in Bonn und war dann Assistent in Bonn, an der Cornell University, am… …   Deutsch Wikipedia

  • Физика за пределами Стандартной модели — В этой статье не хватает ссылок на источники информации. Информация должна быть проверяема, иначе она может быть поставлена под сомнение и удалена. Вы можете …   Википедия

  • Bariogénesis — Saltar a navegación, búsqueda En cosmología física, la bariogénesis es el término genérico utilizado para referirse a los hipotéticos procesos físicos que produjeron una asimetría entre bariones y anti bariones durante los primeros instantes de… …   Wikipedia Español

Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”