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## Revista mexicana de física

##
*versión impresa* ISSN 0035-001X

### Rev. mex. fis. vol.53 supl.2 México feb. 2007

**Preface**

**Prefacio**

The present collection of scientific papers were presented during the *V Workshop of the Gravity and Mathematical Physics Division of the Mexican Physical Society *(V Taller de la Division de Gravitacion y Fisica Matematica (DGFM) de la Sociedad Mexicana de Fisica (SMF)), which was held at the end of November 2003. The workshop took place in the City of Morelia, Michoacan, in the University Cultural Center of the Universidad Michoacana de San Nicolas Hidalgo (UMSNH).

In the months following the *V Workshop, *one of the participants, Dr. Nail Sibgatullin, finally died after a prolonged illness. Given the collaboration Dr. Sibgatullin had with several members of the DGFM community, the editors have decided to dedicate this number to his memory. Dr. Sibgatullin was an important relativist in his home country (Russia), as can be seen from the brief biographical sketch that accompanies this publication. In this way, the DGFM, its members and guests, and the journal of the SMF, play homage to a distinguished professor.

The papers presented here have all been refereed, and constitute a small sample of the research that is done in the field of gravitation and mathematical physics in Mexico, naturally always within the higher context of international science, as can be seen from the list of authors.

We want to thank the support from a number of institutions that made possible the *V Workshop, *(UMSNH, SMF, CONACYT, ININ, ICN–UNAM, CINVESTAV, UAM–I), as well as Dr. Astorga, director of the Institute of Physics and Mathematics, also the School of Physics of UMSNH and the rest of the local organizing committee. Without their help it would have been impossible to hold the workshop.

Miguel Alcubierre

Jorge L. Cervantes–Cota

Merced Montesinos

Ulises Nucamendi

Victor Villanueva

**In Memoriam**

**Nail Sibgatullin: His Life and His Method**

**The date 12th of March 2004 will be remembered by the Russian, Mexican and international scientific community as the date of the tragic loss of one of their brilliant members: Nail Sibgatullin died on that day after struggling courageously for nearly two years with cancer.**

Nail Sibgatullin was born on May 27th, 1943, in the Russia's city Kazan. In 1960 he finished secondary school with honors and in the same year he entered the Faculty of Mechanics and Mathematics of Kazan State University, which is well–known for its scientific tradition, as N. Lobachevsky and A. Petrov worked there in different years.

From the start of his stay at that University, Nail demonstrated his outstanding abilities in mathematics: the standard textbooks were too simple for him and he was allowed, as a rare exception, to work out and follow his own individual advanced program of studies. After his graduation from Kazan University with distinctions in 1965, he moved to Moscow where he entered the Department of Hydrodynamics of the Lomonosov Moscow State University as a PhD student, working under the supervision of the famous Russian Academician L. Sedov. Nail obtained his PhD in 1969, and ten years later received the title of Doctor of Sciences in mathematics and physics. He worked at the Department of Hydrodynamics for nearly forty years, the last twenty of which he occupied the position of full Professor.

Nail Sibgatullin had a very wide range of scientific interests: He successfully worked in theoretical mechanics, gas dynamics, pure and applied mathematics, theoretical physics, relativistic astrophysics and cosmology. He published over one hundred articles and two books. The Russian Academy of Sciences awarded him twice, in 1976 and 1977, with gold medals for scientific excellence.

Nail received the widest international recognition for his method of constructing exact solutions of the Einstein–Maxwell equations, a method developed and described in his monograph "Oscillations and Waves in Strong Gravitational and Electromagnetic Fields", and which can be considered as the most powerful modern solution generating technique. In the case of the gravitational and electromagnetic fields with axial symmetry, it permits the construction of exact solutions using as the departure point their behavior on the symmetry axis. Sibgatullin's method proved to be extremely fruitful in applications. Among the problems solved with its help one can mention the first magnetized generalizations of rotating black hole solutions with Minkowski asymptotic behavior at spatial infinity, the electro–vacuum solution describing the exterior field of *N *Kerr–Newman black holes located on the symmetry axis, as well as a variety of equilibrium problems in many body configurations. In particular, Sibgatullin's method played a crucial role in the work in which E. Ruiz and I proved a theorem on the impossibility of equilibrium states between two Kerr black holes with positive masses, due to the balance of the gravitational attractive and spin–spin repulsive forces. A very interesting physical effect was obtained in the article of N. Sibgatullin and R. Sunyaev: A subtle analysis of a newly derived exact solution revealed that the amount of energy liberated during the accretion of matter onto a neutron star may exceed considerably the amount of energy released during the accretion process onto a black hole. Sibgatullin's method is also applicable to the case of interacting gravitational and electromagnetic waves, allowing for the inclusion of massless neutrino fields in the general scheme. No doubt, Sibgatullin's remarkable approach will prove to be very efficient for finding exact solutions of a wide class of nonlinear systems in the future.

Nail Sibgatullin was a broadly educated person. He played violin and spoke six languages. He visited Mexico several times, the last time in 2002 when he came within the framework of the CONACYT program "Catedras Patrimoniales" to work in CINVESTAV–IPN with Alberto García and me. During his stay at the Physics Department he did not restrict his activity exclusively to considering problems familiar to him, but he was also investigating new topics of astronomy, astrophysics and potential theory. He was constantly in search for new "vivid" problems to which he would be able to apply his vast experience and outstanding mathematical abilities. Even the horrible disease which suddenly stroke him did not affect his enthusiasm toward science. Nail spent the last day of his life at the Physics Department attending the defense of a PhD thesis.

V.S. Manko