Jacob Bekenstein in 2009
|Born||May 1, 1947|
Mexico City, Mexico
|Died||August 16, 2015 68) (aged|
|Alma mater|| Princeton University |
Polytechnic Institute of Brooklyn
|Known for||Black hole thermodynamics|
|Institutions|| Hebrew University of Jerusalem |
Ben-Gurion University of the Negev
|Doctoral advisor||John Wheeler|
Jacob David Bekenstein (Hebrew : יעקב בקנשטיין; May 1, 1947 – August 16, 2015) was a Mexican-born Israeli-American theoretical physicist who made fundamental contributions to the foundation of black hole thermodynamics and to other aspects of the connections between information and gravitation.
Hebrew is a Northwest Semitic language native to Israel; the modern version of which is spoken by over 9 million people worldwide. Historically, it is regarded as the language of the Israelites and their ancestors, although the language was not referred to by the name Hebrew in the Tanakh. The earliest examples of written Paleo-Hebrew date from the 10th century BCE. Hebrew belongs to the West Semitic branch of the Afroasiatic language family. Hebrew is the only living Canaanite language left, and the only truly successful example of a revived dead language.
In physics, black hole thermodynamics is the area of study that seeks to reconcile the laws of thermodynamics with the existence of black-hole event horizons. As the study of the statistical mechanics of black-body radiation led to the advent of the theory of quantum mechanics, the effort to understand the statistical mechanics of black holes has had a deep impact upon the understanding of quantum gravity, leading to the formulation of the holographic principle.
Physical information is a form of information. In physics, it refers to the information of a physical system. Physical information is an important concept used in a number of fields of study in physics. For example, in quantum mechanics, the form of physical information known as quantum information is used in many descriptions of quantum phenomena, such as quantum observation, quantum entanglement and the causal relationship between quantum objects that carry out either or both close and long-range interactions with one another.
Jacob Bekenstein was born in Mexico City to Joseph and Esther (née Vladaslavotsky), Polish Jews who immigrated to Mexico.He moved to the United States during his early life, gaining U.S. citizenship in 1968. He was also a citizen of Israel.
Mexico City, or the City of Mexico, is the capital of Mexico and the most populous city in North America. It is one of the most important cultural and financial centres in the Americas. It is located in the Valley of Mexico, a large valley in the high plateaus in the center of Mexico, at an altitude of 2,240 meters (7,350 ft). The city has 16 boroughs.
The Poles, commonly referred to as the Polish people, are a nation and West Slavic ethnic group native to Poland in Central Europe who share a common ancestry, culture, history, and are native speakers of the Polish language. The population of self-declared Poles in Poland is estimated at 37,394,000 out of an overall population of 38,538,000, of whom 36,522,000 declared Polish alone.
The United States of America (USA), commonly known as the United States or America, is a country comprising 50 states, a federal district, five major self-governing territories, and various possessions. At 3.8 million square miles, the United States is the world's third or fourth largest country by total area and is slightly smaller than the entire continent of Europe's 3.9 million square miles. With a population of more than 327 million people, the U.S. is the third most populous country. The capital is Washington, D.C., and the most populous city is New York City. Forty-eight states and the capital's federal district are contiguous in North America between Canada and Mexico. The State of Alaska is in the northwest corner of North America, bordered by Canada to the east and across the Bering Strait from Russia to the west. The State of Hawaii is an archipelago in the mid-Pacific Ocean. The U.S. territories are scattered about the Pacific Ocean and the Caribbean Sea, stretching across nine official time zones. The extremely diverse geography, climate, and wildlife of the United States make it one of the world's 17 megadiverse countries.
Bekenstein attended the Polytechnic Institute of Brooklyn, now known as the New York University Polytechnic School of Engineering, obtaining both an undergraduate degree and a Master of Science degree in 1969. He went on to receive a Doctor of Philosophy degree from Princeton University, working under the direction of John Archibald Wheeler, in 1972.
A Master of Science is a master's degree in the field of science awarded by universities in many countries or a person holding such a degree. In contrast to the Master of Arts degree, the Master of Science degree is typically granted for studies in sciences, engineering and medicine and is usually for programs that are more focused on scientific and mathematical subjects; however, different universities have different conventions and may also offer the degree for fields typically considered within the humanities and social sciences. While it ultimately depends upon the specific program, earning a Master of Science degree typically includes writing a thesis.
A Doctor of Philosophy is the highest university degree that is conferred after a course of study by universities in most English-speaking countries. PhDs are awarded for programs across the whole breadth of academic fields. As an earned research degree, those studying for a PhD are usually required to produce original research that expands the boundaries of knowledge, normally in the form of a thesis or dissertation, and defend their work against experts in the field. The completion of a PhD is often a requirement for employment as a university professor, researcher, or scientist in many fields. Individuals who have earned a Doctor of Philosophy degree may, in many jurisdictions, use the title Doctor or, in non-English-speaking countries, variants such as "Dr. phil." with their name, although the proper etiquette associated with this usage may also be subject to the professional ethics of their own scholarly field, culture, or society. Those who teach at universities or work in academic, educational, or research fields are usually addressed by this title "professionally and socially in a salutation or conversation." Alternatively, holders may use post-nominal letters such as "Ph.D.", "PhD", or "DPhil". It is, however, considered incorrect to use both the title and post-nominals at the same time.
Princeton University is a private Ivy League research university in Princeton, New Jersey. Founded in 1746 in Elizabeth as the College of New Jersey, Princeton is the fourth-oldest institution of higher education in the United States and one of the nine colonial colleges chartered before the American Revolution. The institution moved to Newark in 1747, then to the current site nine years later, and renamed itself Princeton University in 1896.
Bekenstein had three children with his wife, Bilha. All three children, Yehonadav, Uriya and Rivka Bekenstein, became scientists.Bekenstein was known as a religious man and a believer, being quoted as saying: "I look at the world as a product of God, He set very specific laws and we delight in discovering them through scientific work."
In monotheistic thought, God is conceived of as the supreme being, creator deity, and principal object of faith. God is usually conceived as being omniscient (all-knowing), omnipotent (all-powerful), omnipresent (all-present) and as having an eternal and necessary existence. These attributes are used either in way of analogy or are taken literally. God is most often held to be incorporeal (immaterial). Incorporeality and corporeality of God are related to conceptions of transcendence and immanence of God, with positions of synthesis such as the "immanent transcendence".
By 1972, Bekenstein had published three influential papers about the black hole stellar phenomenon, postulating the no-hair theorem and presenting a theory on black hole thermodynamics. In the years to come, Bekenstein continued his exploration of black holes, publishing papers on their entropy and quantum mass.
The no-hair theorem postulates that all black hole solutions of the Einstein–Maxwell equations of gravitation and electromagnetism in general relativity can be completely characterized by only three externally observable classical parameters: mass, electric charge, and angular momentum. All other information about the matter which formed a black hole or is falling into it, "disappears" behind the black-hole event horizon and is therefore permanently inaccessible to external observers. Physicist John Archibald Wheeler expressed this idea with the phrase "black holes have no hair" which was the origin of the name. In a later interview, John Wheeler says that Jacob Bekenstein coined this phrase.
In statistical mechanics, entropy is an extensive property of a thermodynamic system. It is closely related to the number Ω of microscopic configurations that are consistent with the macroscopic quantities that characterize the system. Under the assumption that each microstate is equally probable, the entropy is the natural logarithm of the number of microstates, multiplied by the Boltzmann constant kB. Formally,
Bekenstein was a postdoctoral fellow at the University of Texas at Austin from 1972 to 1974. He then immigrated to Israel to lecture and teach at Ben-Gurion University in Beersheba. In 1978, he became a full professor and in 1983, head of the astrophysics department.
The University of Texas at Austin is a public research university in Austin, Texas. It was founded in 1883 and is the flagship institution of the University of Texas System. The University of Texas was inducted into the Association of American Universities in 1929, becoming only the third university in the American South to be elected. The institution has the nation's eighth-largest single-campus enrollment, with over 50,000 undergraduate and graduate students and over 24,000 faculty and staff.
Aliyah is the immigration of Jews from the diaspora to the Land of Israel. Also defined as "the act of going up"—that is, towards Jerusalem—"making Aliyah" by moving to the Land of Israel is one of the most basic tenets of Zionism. The opposite action, emigration from the Land of Israel, is referred to in Hebrew as yerida ("descent"). The State of Israel's Law of Return gives Jews and their descendants automatic rights regarding residency and Israeli citizenship.
Ben-Gurion University of the Negev (BGU), is a public research university in Beersheba, Israel. Ben-Gurion University of the Negev has five campuses: the Marcus Family Campus, Beer Sheva; the David Bergmann Campus, Beer Sheva; the David Tuviyahu Campus, Beer Sheva; the Sede Boqer Campus, and Eilat Campus.
In 1990, he became a professor at the Hebrew University of Jerusalem and was appointed head of its theoretical physics department three years later.He was elected to the Israel Academy of Sciences and Humanities in 1997. He was a visiting scholar at the Institute for Advanced Study in 2009 and 2010.
In addition to lectures and residencies around the world,Bekenstein continued to serve as Polak professor of theoretical physics at the Hebrew University until his death at the age of 68, in Helsinki, Finland. He died unexpectedly on August 16, 2015, just months after receiving the American Physical Society's Einstein Prize "for his ground-breaking work on black hole entropy, which launched the field of black hole thermodynamics and transformed the long effort to unify quantum mechanics and gravitation".
In 1972, Bekenstein was the first to suggest that black holes should have a well-defined entropy. He wrote that a black hole's entropy was proportional to the area of its (the black hole's) event horizon. Bekenstein also formulated the generalized second law of thermodynamics, black hole thermodynamics, for systems including black holes. Both contributions were affirmed when Stephen Hawking (and, independently, Zeldovich and others) proposed the existence of Hawking radiation two years later. Hawking had initially opposed Bekenstein's idea on the grounds that a black hole could not radiate energy and therefore could not have entropy.However, in 1974, Hawking performed a lengthy calculation that convinced him that particles can indeed be emitted from black holes. Today this is known as Hawking radiation. Bekenstein's doctoral adviser, John Archibald Wheeler, also worked with him to develop the no-hair theorem, a reference to Wheeler's saying that "black holes have no hair," in the early 1970s. Bekenstein's suggestion was proven unstable, but it was influential in the development of the field.
Based on his black-hole thermodynamics work, Bekenstein also demonstrated the Bekenstein bound: there is a maximum to the amount of information that can potentially be stored in a given finite region of space which has a finite amount of energy (which is similar to the holographic principle).
In 1982, Bekenstein developed a rigorous framework to generalize the laws of electromagnetism to handle inconstant physical constants. His framework replaces the fine-structure constant by a scalar field. However, this framework for changing constants did not incorporate gravity.
In 2004, Bekenstein boosted Mordehai Milgrom's theory of Modified Newtonian Dynamics (MOND) by developing a relativistic version. It is known as TeVeS for Tensor/Vector/Scalar and it introduces three different fields in space time to replace the one gravitational field.
The holographic principle is a tenet of string theories and a supposed property of quantum gravity that states that the description of a volume of space can be thought of as encoded on a lower-dimensional boundary to the region—such as a light-like boundary like a gravitational horizon. First proposed by Gerard 't Hooft, it was given a precise string-theory interpretation by Leonard Susskind who combined his ideas with previous ones of 't Hooft and Charles Thorn. As pointed out by Raphael Bousso, Thorn observed in 1978 that string theory admits a lower-dimensional description in which gravity emerges from it in what would now be called a holographic way. The prime example of holography is the AdS/CFT correspondence.
A gravitational singularity, spacetime singularity or simply singularity is a location in spacetime where the gravitational field of a celestial body is predicted to become infinite by general relativity in a way that does not depend on the coordinate system. The quantities used to measure gravitational field strength are the scalar invariant curvatures of spacetime, which includes a measure of the density of matter. Since such quantities become infinite within the singularity, the laws of normal spacetime cannot exist.
Hawking radiation is black-body radiation that is predicted to be released by black holes, due to quantum effects near the event horizon. It is named after the theoretical physicist Stephen Hawking, who provided a theoretical argument for its existence in 1974.
In string theory, D-branes, short for Dirichlet membrane, are a class of extended objects upon which open strings can end with Dirichlet boundary conditions, after which they are named. D-branes were discovered by Dai, Leigh and Polchinski, and independently by Hořava in 1989. In 1995, Polchinski identified D-branes with black p-brane solutions of supergravity, a discovery that triggered the Second Superstring Revolution and led to both holographic and M-theory dualities.
Andrew Eben Strominger is an American theoretical physicist who is the director of Harvard's Center for the Fundamental Laws of Nature. He has made significant contributions to quantum gravity and string theory. These include his work on Calabi-Yau compactification and topology change in string theory, and on the stringy origin of black hole entropy. He is a senior fellow at the Society of Fellows, and is the Gwill E. York Professor of Physics.
An order of magnitude is a factor of ten. A quantity growing by four orders of magnitude implies it has grown by a factor of 10,000 or 104.
In theoretical physics, an extremal black hole is a black hole with the minimal possible mass that can be compatible with a given charge and angular momentum. In other words, this is the smallest possible black hole that can exist while rotating at a given fixed constant speed.
Micro black holes, also called quantum mechanical black holes or mini black holes, are hypothetical tiny black holes, for which quantum mechanical effects play an important role. The concept that black holes may exist that are smaller than stellar mass was introduced in 1971 by Stephen Hawking.
The black hole information paradox is a puzzle resulting from the combination of quantum mechanics and general relativity. Calculations suggest that physical information could permanently disappear in a black hole, allowing many physical states to devolve into the same state. This is controversial because it violates a core precept of modern physics—that in principle the value of a wave function of a physical system at one point in time should determine its value at any other time. A fundamental postulate of the Copenhagen interpretation of quantum mechanics is that complete information about a system is encoded in its wave function up to when the wave function collapses. The evolution of the wave function is determined by a unitary operator, and unitarity implies that information is conserved in the quantum sense.
In physics, the Bekenstein bound is an upper limit on the entropy S, or information I, that can be contained within a given finite region of space which has a finite amount of energy—or conversely, the maximal amount of information required to perfectly describe a given physical system down to the quantum level. It implies that the information of a physical system, or the information necessary to perfectly describe that system, must be finite if the region of space and the energy is finite. In computer science, this implies that there is a maximal information-processing rate for a physical system that has a finite size and energy, and that a Turing machine with finite physical dimensions and unbounded memory is not physically possible.
The Weyl curvature hypothesis, which arises in the application of Albert Einstein's general theory of relativity to physical cosmology, was introduced by the British mathematician and theoretical physicist Sir Roger Penrose in an article in 1979 in an attempt to provide explanations for two of the most fundamental issues in physics. On the one hand one would like to account for a universe which on its largest observational scales appears remarkably spatially homogeneous and isotropic in its physical properties, on the other hand there is the deep question on the origin of the second law of thermodynamics.
There are close parallels between the mathematical expressions for the thermodynamic entropy, usually denoted by S, of a physical system in the statistical thermodynamics established by Ludwig Boltzmann and J. Willard Gibbs in the 1870s, and the information-theoretic entropy, usually expressed as H, of Claude Shannon and Ralph Hartley developed in the 1940s. Shannon commented on the similarity upon publicizing information theory in A Mathematical Theory of Communication.
Ruppeiner geometry is thermodynamic geometry using the language of Riemannian geometry to study thermodynamics. George Ruppeiner proposed it in 1979. He claimed that thermodynamic systems can be represented by Riemannian geometry, and that statistical properties can be derived from the model.
Entropic gravity, also known as emergent gravity, is a theory in modern physics that describes gravity as an entropic force—a force with macro-scale homogeneity but which is subject to quantum-level disorder—and not a fundamental interaction. The theory, based on string theory, black hole physics, and quantum information theory, describes gravity as an emergent phenomenon that springs from the quantum entanglement of small bits of spacetime information. As such, entropic gravity is said to abide by the second law of thermodynamics under which the entropy of a physical system tends to increase over time.
A black hole firewall is a hypothetical phenomenon where an observer falling into a black hole encounters high-energy quanta at the event horizon. The "firewall" phenomenon was proposed in 2012 by physicists Ahmed Almheiri, Donald Marolf, Joseph Polchinski, and James Sully as a possible solution to an apparent inconsistency in black hole complementarity. The proposal is sometimes referred to as the AMPS firewall, an acronym for the names of the authors of the 2012 paper. The use of a firewall to resolve this inconsistency remains controversial, with high-energy physicists divided as to the solution to the paradox. 2016 LIGO observations provided tentative evidence of a firewall or of some other phenomenon that in extreme cases seems to violate relativity.
The Ryu-Takayanagi conjecture is a conjecture within holography that posits a quantitative relationship between the entanglement entropy of a conformal field theory and the geometry of an associated Anti-de Sitter spacetime. The formula characterizes "holographic screens" in the bulk; that is, it specifies which regions of the bulk geometry are "responsible to particular information in the dual CFT". The conjecture is named after Shinsei Ryu and Tadashi Takayanagi, who jointly published the result in 2006. As a result, the authors were awarded the 2015 New Horizons in Physics Prize for "fundamental ideas about entropy in quantum field theory and quantum gravity". The formula was generalized to a covariant form in 2007.
Frans Pretorius is a South African and Canadian physicist, specializing in computer simulations in astrophysics and numerical solutions of Einstein's field equations.
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