Tsvi Piran

Tsvi Piran

Tsvi Piran (born May 6, 1949 in Tel Aviv ) is an Israeli astrophysicist, known for work on gamma-ray flashes (GRB).

Life

Piran studied mathematics and physics at Tel Aviv University from 1967 with a bachelor's degree in 1970. He then did his military service until 1972 and received his doctorate in 1976 at Tel Aviv University in astrophysics with Jacob Shaham and Joseph Katz. The dissertation was on modeling gamma-ray bursts from instabilities around black holes. As a post-doctoral student he was with Dennis Sciama in Oxford in 1976/77 and with Bryce DeWitt at the University of Texas at Austin from 1977 to 1979 , where he worked on numerical relativity and jets in active galactic nuclei (AGN) and became an assistant professor. 1980 to 1987 he was at the Institute for Advanced Study and at the same time professor at the Hebrew University .

From 1990 to 1993 he was at the Center for Astrophysics at Harvard University and from 1998/99 visiting professor at Columbia University and New York University . In 2004/05 he was Moore Scholar at Caltech . From 2005 to 2009 he was Dean of the School of Business Administration at the Hebrew University.

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In 1988 he and D. Eichler, Mario Livio and David Schramm proposed that GRBs arise when neutron stars orbiting each other merge, a theory that is widely accepted today. He developed the fireball model - originally by Bohdan Paczyński and J. Goodman from the 1980s - of the GRBs, and he hypothesized that GRBs are associated with the formation of black holes. Piran authored reviews of GRBs that are standard literature. He was an early advocate of the origin of GRBs outside of our galaxy (as was Bohdan Paczyński), which was proven in 1997 by measuring the redshift in the afterglow of the GRBs, which he also played a part in. In 1999 Piran demonstrated the formation of jets in GRBs and investigated the destruction of stars in the tidal forces of a supermassive black hole (tidal disruption events) as a possible cause of certain GRBs.

In 2014 he and Raul Jimenez explored the role of GRBs in the development of life. He calculated a 50 percent chance that a GRB caused a mass extinction on Earth in the past 500 million years. The effects of GRBs near the galactic center are greatest, making the inner galaxy uninhabitable. The likelihood of more deadly GRBs is 95 percent within a 4 kilo parsec radius of the center and only drops below 50 percent at 10 kilo parsecs. According to them, life similar to Earth is only possible in the outer areas of large galaxies. This is a possibility in only around 10 percent of galaxies. In addition, at redshifts, life like on Earth is not possible because the GRBs are more common and the galaxies are smaller. ${\displaystyle z>0,5}$

In 1985 he was one of the first to calculate the gravitational waves in the formation of rotating black holes in a gravitational collapse with numerical relativity. The calculations predicted relaxation to the quasinormal modes of the final state of the rotating black hole.

In 1985 he and Ruth Williams explained that inflation is a generic phenomenon with massive scalar fields independent of the potential. but also that for cosmological inflation in the currently discussed scenarios specific initial conditions are necessary.

With Shahar Hod he showed in 1998 that the internal structure of black holes (modeled from a gravitational collapse of charged scalar fields) is unstable (formation of inflation).

In 1990 he was the first to show with Ofer Lahav and Robert Nemiroff that the distribution of galaxies in the universe depends on the type of galaxies.

With Amos Ori in 1990 he showed the generic emergence of naked singularities (and thus a violation of the Cosmic Censorship Hypothesis) during the gravitational collapse of barotropic ideal liquids (in contrast to the classic Oppenheimer-Snyder scenario that the matter is modeled as dust).

Prices

In 2009 he received an ERC Advanced Grant (and another) and in 2019 the EMET award .

Fonts (selection)

• with RF Stark: Gravitational-wave emission from rotating gravitational collapse, Physical Review Letters, Volume 55, 1985, pp. 891-894.
• with Ruth Williams: Inflation in universes with a massive scalar field, Physics Letters B, Volume 163, 1985, pp. 331-335
• with D. Eichler, M. Livio , David Schramm : Nucleosynthesis, neutrino bursts and gamma-rays from coalescing neutron stars, Nature, Volume 340, 1988, pp. 126-128.
• with J. Bahcall , J. Ostriker : Towards Understanding Gamma-Ray Bursts, Nature, Volume 340, 1989, pp. 126-128.
• with Shemi Arnotz: The appearance of cosmic fireballs, Astrophysical Journal Letters, Volume 365, 1990, pp. 55-88.
• with Ofer Lahav, Robert J. Nemiroff: Relative bias parameters from angular correlations of optical and IRAS galaxies, Astrophysical Journal, Volume 350, 1990, pp. 119-124
• with Amos Ori: Naked singularities and other features of self-similar general-relativistic gravitational collapse, Physical Review D, Volume 42, 1990, pp. 1068-1090. Abstract
• with Dalia Goldwirth: Initial conditions for inflation, Physics Reports, Volume 214, 1992, pp. 223-292, abstract
• with C. Kochanek: Gravitational Waves and Gamma-Ray Bursts, Astrophysical Journal Letters, Volume. 417, 1993, L17-L23, Arxiv
• Toward understanding gamma-ray bursts, in: JN Bahcall, J. Ostriker (Eds.), Unsolved Problems in Astrophysics, 1997, p. 343.
• with Shahar Hod: Mass Inflation in Dynamical Gravitational Collapse of a Charged Scalar Field, Physical Review Letters, Volume 81, 1998, pp. 1554–1557. Arxiv
• with R. Sari, R. Narayan: Spectra and Light Curves of Gamma-Ray Burst Afterglows, Astrophysical Journal Letters, Volume 497, 1998, pp. L 17-20, Arxiv
• Gamma-ray bursts and the fireball model, Physics Reports, Volume 314, 1999, pp. 575-667, Arxiv
• The physics of gamma-ray bursts, Reviews of Modern Physics, Volume 76, 1999, pp. 1143-1210, Arxiv
• with R. Sari JP Halpern: Jets in Gamma Ray Bursts, Astrophysical Journal Letters, Volume 519, 1999, pp. L 17-20. Arxiv
• with D. Guetta: The BATSE-Swift luminosity and redshift distributions of short-duration GRBs, Astronomy and Astrophysics, Volume 453, 2006, pp. 823-828, Arxiv
• with J. Krolik: Swift J1644 + 57: A White Dwarf Tidally Disrupted by a Black Hole?, Astroph. J., Volume 743, 2011, p. 134, Arxiv ${\displaystyle 10^{4}M_{odot}}$
• with R. Jimenez: Possible Role of Gamma Ray Bursts on Life Extinction in the Universe, Physical Review Letters, Volume 113, 2014, p. 231102, Arxiv
• with K. Ioka, K. Hotokezaka: Are Ultra-Long Gamma-Ray Bursts Caused by Blue Supergiant Collapsars, Newborn Magnetars, or White Dwarf Tidal Disruption Events ?, Astrophysical Journal, Volume 833, 2016, p. 110, Arxiv

He has been one of the editors (with Steven Weinberg, among others ) of several volumes of the anthologies of the Jerusalem Winter School for Theoretical Physics published by World Scientific since the 1980s .

Web links

• Homepage, Hebrew University