SINP is an autonomous research institute under the administrative control of the Department of Atomic Energy, Government of India .The institute is governed by a governing council headed by the chairman of the atomic energy commission of India, in accordance with a tripartite agreement signed by the government of India, government of west Bengal and the Calcutta university in August 1992. The institute is known as a centre for conducting research for doctoral degrees and providing facilities for teaching and research in physical and biological sciences. The chairman of the Atomic Energy Commission, India (and Secretary, DAE, government of India) chairs the governing council with members comprising three scientists nominated by the DAE, two representatives of the DAE, two nominees of CU, one nominee of government of West Bengal and the director of the institute with Registrar as the ex-officio secretary to the governing council.

Adapted from the Wikipedia article Saha Institute of Nuclear Physics, under the G. N. U. Free Documentation License. Please also see http://en.wikipedia.org/wiki

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Models based on general relativity play an important role in astrophysics, and the success of these models is further testament to the theory’s validity.

Gravitational lensing

Since light is deflected in a gravitational field, it is possible for the light of a distant object to reach an observer along two or more paths. For instance, light of a very distant object such as a quasar can pass along one side of a massive galaxy and be deflected slightly so as to reach an observer on Earth, while light

passing along the opposite side of that same galaxy is deflected as well, reaching the same observer from a slightly different direction. As a result, that particular observer will see one astronomical object in two different places in the night sky. This kind of focussing is well-known when it comes to optical lenses, and hence the corresponding gravitational effect is called gravitational lensing.

Observational astronomy uses lensing effects as an important tool to infer properties of the lensing object. Even in cases where that object is not directly visible, the shape of a lensed image provides information about the mass distribution responsible for the light deflection. In particular, gravitational lensing provides one way to measure the distribution of dark matter, which does not give off light and can be observed only by its gravitational effects. One particularly interesting application are large-scale observations, where the lensing masses are spread out over a significant fraction of the observable universe, and can be used to obtain information about the large-scale properties and evolution of our cosmos.

Gravitational waves

Gravitational waves, a direct consequence of Einstein’s theory, are distortions of geometry which propagate at the speed of light, and can be thought of as ripples in space-time. They should not be confused with the gravity waves of fluid dynamics, which are a different concept.

Indirectly, the effect of gravitational waves has been detected in observations of specific binary stars. Such pairs of stars orbit each other and, as they do so, gradually lose energy by emitting gravitational waves. For ordinary stars like our sun, this energy loss would be too small to be detectable, but this energy loss was observed in 1974 in a binary pulsar called PSR1913+16. In such a system, one of the orbiting stars is a pulsar. This has two consequences: a pulsar is an extremely dense object known as a neutron star, for which gravitational wave emission is much stronger than for ordinary stars. Also, a pulsar emits a narrow beam of electromagnetic radiation from its magnetic poles. As the pulsar rotates, its beam sweeps over the Earth, where it is seen as a regular series of radio pulses, just as a ship at sea observes regular flashes of light from the rotating light in a lighthouse. This regular pattern of radio pulses functions as a highly accurate “clock”. It can be used to time the double star’s orbital period, and it reacts sensitively to distortions of space-time in its immediate neighborhood.

The discoverers of PSR1913+16, Russell Hulse and Joseph Taylor, were awarded the Nobel Prize in Physics in 1993. Since then, several other binary pulsars have been found. The most useful are those in which both stars are pulsars, since they provide the most accurate tests of general relativity.

Currently, one major goal of research in relativity is the direct detection of gravitational waves. To this end, a number of land-based gravitational wave detectors are in operation, and a mission to launch a space-based detector, LISA, is currently under development, with a precursor mission (LISA Pathfinder) due for launch in June 2011. If gravitational waves are detected, they could be used to obtain information about compact objects such as neutron stars and black holes, and also to probe the state of the early universe fractions of a second after the Big Bang.

Black holes

When mass is concentrated into a sufficiently compact region of space, general relativity predicts the formation of a black hole& – a region of space with a gravitational attraction so strong that not even light can escape. Certain types of black holes are thought to be the final state in the evolution of massive stars. On the other hand, supermassive black holes with the mass of millions or billions of Suns are assumed to reside in the cores of most galaxies, and they play a key role in current models of how galaxies have formed over the past billions of years.

Matter falling onto a compact object is one of the most efficient mechanisms for releasing energy in the form of radiation, and matter falling onto black holes is thought to be responsible for some of the brightest astronomical phenomena imaginable. Notable examples of great interest to astronomers are quasars and other types of active galactic nuclei. Under the right conditions, falling matter accumulating around a black hole can lead to the formation of jets, in which focused beams of matter are flung away into space at speeds near that of light.

There are several properties that make black holes most promising sources of gravitational waves. One reason is that black holes are the most compact objects that can orbit each other as part of a binary system; as a result, the gravitational waves emitted by such a system are especially strong. Another reason follows from what are called black hole uniqueness theorems: over time, black holes retain only a minimal set of distinguishing features (since different hair styles are a crucial part of what gives different people their different appearances, these theorems have become known as “no hair” theorems). For instance, in the long term, the collapse of a hypothetical matter cube will not result in a cube-shaped black hole. Instead, the resulting black hole will be indistinguishable from a black hole formed by the collapse of a spherical mass, but with one important difference: in its transition to a spherical shape, the black hole formed by the collapse of a cube will emit gravitational waves.

Cosmology

One of the most important aspects of general relativity is that it can be applied to the universe as a whole. A key point is that, on large scales, our universe appears to be constructed along very simple lines: All current observations suggest that, on average, the structure of the cosmos should be approximately the same, regardless of an observer’s location or direction of observation: the universe is approximately homogeneous and isotropic. Such comparatively simple universes can be described by simple solutions of Einstein’s equations. The current cosmological models of the universe are obtained by combining these simple solutions to general relativity with theories describing the properties of the universe’s matter content, namely thermodynamics, nuclear- and particle physics. According to these models, our present universe emerged from an extremely dense high-temperature state (the Big Bang)

roughly 14 billion years ago, and has been expanding ever since.

Einstein’s equations can be generalized by adding a term called the cosmological constant. When this term is present, empty space itself acts as a source of attractive or, unusually, repulsive gravity. Einstein originally introduced this term in his pioneering 1917 paper on cosmology, with a very specific motivation: contemporary cosmological thought held the universe to be static, and the additional term was required for constructing static model universes within the framework of general relativity. When it became apparent that the universe is not static, but expanding, Einstein was quick to discard this additional term; prematurely, as we know today: From about 1998 on, a steadily accumulating body of astronomical evidence has shown that the expansion of the universe is accelerating in a way that suggests the presence of a cosmological constant or, equivalently, of a dark energy with specific properties that pervades all of space.

Adapted from the Wikipedia article Introduction to general relativity, under the G. N. U. Free Documentation License. Please also see http://en.wikipedia.org/wiki

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Nuclear Physics A

*Current Contents/Physics, Chemical, & Earth Sciences

*Scopus

*Zentralblatt MATH

Nuclear Physics B

*Chemical Abstracts

*Current Contents/Physics, Chemical, & Earth Sciences

*Scopus

*Zentralblatt MATH

Adapted from the Wikipedia article Nuclear Physics (journal), under the G. N. U. Free Documentation License. Please also see http://en.wikipedia.org/wiki

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While many fissionable isotopes exist in nature, the only usefully fissile isotope found in any quantity is 235U. About 0.7% of the uranium in most ores is the 235 isotope, and about 99.3% is the inert 238 isotope. For most uses as a nuclear fuel, uranium must be ”enriched” – purified so that it contains a higher percentage of 235U. Because 238U absorbs fast neutrons, the critical mass needed to sustain a chain reaction increases as the 238U content increases, reaching infinity at 94% 238U (6% 235U).

Concentrations lower than 6% 235U cannot go fast critical, though they are usable in a nuclear reactor with a neutron moderator.

A nuclear weapon primary stage using uranium uses HEU enriched to ~90% 235U, though the secondary stage often uses lower enrichments. Nuclear reactors with water moderator can operate with only moderate enrichment of ~5% 235U. Nuclear reactors with heavy water moderation can operate with natural uranium, eliminating altogether the need for enrichment and preventing the fuel from being useful for nuclear weapons; the CANDU power reactors used in Canadian power plants are an example of this type.

Uranium enrichment is difficult because the chemical properties of 235U and 238U are identical, so physical processes such as gaseous diffusion, gas centrifuge or mass spectrometry must be used for isotopic separation based on small differences in mass. Because enrichment is the main technical hurdle to production of nuclear fuel and simple nuclear weapons, enrichment technology is politically sensitive.

Adapted from the Wikipedia article Nuclear reactor physics, under the G. N. U. Free Documentation License. Please also see http://en.wikipedia.org/wiki

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Astrochemistry, the overlap of the disciplines of astronomy and chemistry, is the study of the abundance and reactions of chemical elements and molecules in space, and their interaction with radiation. The formation, atomic and chemical composition, evolution and fate of molecular gas clouds, is of special interest because it is from these clouds that solar systems form.

Infrared astronomy, for example, has revealed that the interstellar medium contains a suite of complex gas-phase carbon compounds called aromatic hydrocarbons, often abbreviated (PAHs or PACs). These molecules composed primarily of fused rings of carbon (either neutral or in an ionized state) are said to be the most common class of carbon compound in the galaxy. They are also the most common class of carbon molecule in meteorites and in cometary and asteroidal dust (cosmic dust). These compounds, as well as the amino acids, nucleobases, and many other compounds in meteorites, carry deuterium and isotopes of carbon, nitrogen, and oxygen that are very rare on earth, attesting to their extraterrestrial origin. The PAHs are thought to form in hot circumstellar environments (around dying carbon rich red giant stars).

The sparseness of interstellar and interplanetary space results in some unusual chemistry, since symmetry-forbidden reactions cannot occur except on the longest of timescales. For this reason, molecules and molecular ions which are unstable on Earth can be highly abundant in space, for example the H3+ ion. Astrochemistry overlaps with astrophysics and nuclear physics in characterizing the nuclear reactions

Adapted from the Wikipedia article Theoretical astronomy, under the G. N. U. Free Documentation License. Please also see http://en.wikipedia.org/wiki

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*”Nuclear Instruments” (1957–1958)

*”Nuclear Instruments and Methods” (1959–1981)

*”Nuclear Instruments and Methods in Physics Research” (1984–Present)

:*”Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment” (1984–Present)

:*”Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms” (1984–Present)

Adapted from the Wikipedia article Nuclear Instruments and Methods in Physics Research, under the G. N. U. Free Documentation License. Please also see http://en.wikipedia.org/wiki

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Nuclear physics is the field of physics that studies the building blocks and interactions of atomic nuclei.

The most commonly known applications of nuclear physics are nuclear power and nuclear weapons, but the research has provided wider applications, including those in medicine (nuclear medicine, magnetic resonance imaging), materials engineering (ion implantation) and archaeology (radiocarbon dating).

The field of particle physics evolved out of nuclear physics and, for this reason, has been included under the same term in earlier times.

Adapted from the Wikipedia article Nuclear physics, under the G. N. U. Free Documentation License. Please also see http://en.wikipedia.org/wiki

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Joint Institute for Nuclear Astrophysics (JINA) in USA is a collaboration between Michigan State University, the University of Notre Dame, and the University of Chicago to address a broad range of experimental, theoretical, and observational questions in nuclear astrophysics. In the fall of 2003, JINA received a five year grant by the National Science Foundation Physics Frontier Center (PFC) program. This funding offers the opportunity for JINA to develop as an intellectual center with the goal enabling swift communication and stimulating collaborations across field boundaries and at the same time providing a focus point in the rapidly growing and diversifying field of nuclear astrophysics .

Nuclear astrophysics focuses on questions at the interface of nuclear physics and astrophysics. It addresses the role of nuclear structure and nuclear reaction processes as engines of stellar evolution and stellar explosions and seeks to find answers to the fundamental questions about the origin of the elements found today throughout the universe. Because of the extreme nature of the stellar conditions, the understanding of these nuclear processes poses an enormous challenge to astrophysics, nuclear theorists, and experimentalists. Advances in experimental nuclear astrophysics now allow physicists to investigate many stellar processes in the laboratory. These advances span a wide range of techniques and facilities. They include innovative methods to measure the extremely slow reactions in the interiors of stars, as well as new facilities to produce the very same exotic, short-lived nuclei that come t

While these experiments are pursued at the accelerator facilities at Notre Dame, Michigan State University, and Argonne National Laboratory, complementary theoretical questions about the macrophysics aspects and conditions of stellar evolution and stellar explosion are addressed by JINA at the University of Chicago, at Notre Dame, and with associated groups at the University of California at Santa Cruz and Santa Barbara, the University of Arizona, Argonne National Laboratory and Los Alamos National Laboratory. This component branches towards fundamental understanding of the processes governing life and death of stars as well as to the identification of unique signatures for present and future observation. Close collaboration and exchange of scientists between these institutions is necessary to address the broad and complex range of scientific goals.

JINA will foster an interdisciplinary approach to the open questions in nuclear astrophysics. It will drive further advances in nuclear physics and astrophysics that are specifically needed to answer open questions in nuclear astrophysics, and it will ensure that advances in individual fields will ultimately lead to progress in our understanding of nuclear astrophysics.

Adapted from the Wikipedia article Joint Institute for Nuclear Astrophysics, under the G. N. U. Free Documentation License. Please also see http://en.wikipedia.org/wiki

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Modern deposits of uranium contain only up to ~0.7% 235U (and ~99.3% 238U), which is not enough to sustain a chain reaction moderated by ordinary water. But 235U has a much shorter half-life (700 million years) than 238U (4.5 billion years), so in the distant past the percentage of 235U was much higher. About two billion years ago, a water-saturated uranium deposit (in what is now the Oklo mine in Gabon, West Africa) underwent a naturally occurring chain reaction that was moderated by groundwater and, presumably, controlled by the negative void coefficient as the water boiled from the heat of the reaction. Uranium from the Oklo mine is about 50% depleted compared to other locations: it is only about 0.3% to 0.7% 235U; and the ore contains traces of stable daughters of long-decayed fission products.

Adapted from the Wikipedia article Nuclear reactor physics, under the G. N. U. Free Documentation License. Please also see http://en.wikipedia.org/wiki

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Tom W. Bonner Prize in Nuclear Physics is an annual prize awarded by the American Physical Society’s Division of Nuclear Physics. Established in 1964, and currently consisting of $7,500 and a certificate, the Bonner Prize was founded in memory of physicist Tom W. Bonner. The aim of the prize, as stated by the American Physical Society is:

:”To recognize and encourage outstanding experimental research in nuclear physics, including the development of a method, technique, or device that significantly contributes in a general way to nuclear physics research.”

The Bonner Prize is generally awarded for individual achievement in experimental research, but can be awarded for exceptional theoretical work and to groups who have contributed to a single accomplishment.

Adapted from the Wikipedia article Tom W. Bonner Prize in Nuclear Physics, under the G. N. U. Free Documentation License. Please also see http://en.wikipedia.org/wiki

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