|
Luboš Motl
Luboš Motl (; born 5 December 1973) is a Czech blogger. He was an assistant professor in physics at Harvard University from 2004 to 2007. His scientific publications were focused on string theory. Life and career Motl was born in Plzeň, present-day Czech Republic. He won a Bronze Medal at the 1992 International Mathematical Olympiad. He received his master's degree from the Charles University in Prague, and his Doctor of Philosophy degree from Rutgers University (2001) and has been a Harvard Junior Fellow (2001–2004) and assistant professor (2004–2007) at Harvard University. In 2007, he left Harvard and returned to the Czech Republic. Although an undergraduate at a Czech university where none of the faculty specialized in string theory, Motl came to the attention of string theorist Thomas Banks in 1996, when Banks read an arXiv posting by Motl on matrix string theory. "I was at first a little annoyed by otl'spaper, because it scooped me," said Banks. "This feeling turne ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Plzeň
Plzeň (), also known in English and German as Pilsen (), is a city in the Czech Republic. It is the Statutory city (Czech Republic), fourth most populous city in the Czech Republic with about 188,000 inhabitants. It is located about west of Prague, at the confluence of four rivers: Mže, Úhlava, Úslava and Radbuza, together forming the Berounka River. Founded as a royal city in the late 13th century, Plzeň became an important town for trade on routes linking Bohemia with Bavaria. By the 14th century it had grown to be the third largest city in Bohemia. The city was besieged three times during the 15th-century Hussite Wars, when it became a centre of resistance against the Hussites. During the Thirty Years' War in the early 17th century the city was temporarily occupied after the Siege of Plzeň. In the 19th century, the city rapidly industrialised and became home to the Škoda Works, which became one of the most important engineering companies in Austria-Hungary and later ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Doctor Of Philosophy
A Doctor of Philosophy (PhD, DPhil; or ) is a terminal degree that usually denotes the highest level of academic achievement in a given discipline and is awarded following a course of Postgraduate education, graduate study and original research. The name of the degree is most often abbreviated PhD (or, at times, as Ph.D. in North American English, North America), pronounced as three separate letters ( ). The University of Oxford uses the alternative abbreviation "DPhil". PhDs are awarded for programs across the whole breadth of academic fields. Since it is an earned research degree, those studying for a PhD are required to produce original research that expands the boundaries of knowledge, normally in the form of a Thesis, dissertation, and, in some cases, defend their work before a panel of other experts in the field. In many fields, the completion of a PhD is typically required for employment as a university professor, researcher, or scientist. Definition In the context o ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Weak Gravity Conjecture
In theoretical physics, the weak gravity conjecture (WGC) is a conjecture regarding the strength gravity can have in a theory of quantum gravity relative to the gauge forces in that theory. It roughly states that gravity should be the weakest force in any consistent theory of quantum gravity. It was first proposed by Nima Arkani-Hamed, Luboš Motl, Alberto Nicolis, and Cumrun Vafa in 2007. Gravity when compared to a U(1) gauge group interaction like electromagnetism, the mildest version of the weak gravity conjecture implies that there exist an object with electric charge ''q'' and mass ''m'' such that \frac\geq\left.\frac\_ where \left.Q/M\_ is the charge-to-mass ratio of an arbitrary large black hole. The conjecture was originally motivated by the fact that black holes should be able to decay. This insensitivity of black hole evaporation to its electric charge suggests that black holes can violate global symmetries and violate global charge conservation. See also * Fundamen ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Loop Quantum Gravity
Loop quantum gravity (LQG) is a theory of quantum gravity that incorporates matter of the Standard Model into the framework established for the intrinsic quantum gravity case. It is an attempt to develop a quantum theory of gravity based directly on Albert Einstein's geometric formulation rather than the treatment of gravity as a mysterious mechanism (force). As a theory, LQG postulates that the structure of space and time is composed of finite loops woven into an extremely fine fabric or network. These networks of loops are called spin networks. The evolution of a spin network, or spin foam, has a scale on the order of a Planck length, approximately 10−35 meters, and smaller scales are meaningless. Consequently, not just matter, but space itself, prefers an atomic structure. The areas of research, which involve about 30 research groups worldwide, share the basic physical assumptions and the mathematical description of quantum space. Research has evolved in two directions ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Quasinormal Mode
Quasinormal modes (QNM) are the modes of energy dissipation of a perturbed object or field, ''i.e.'' they describe perturbations of a field that decay in time. Example A familiar example is the perturbation (gentle tap) of a wine glass with a knife: the glass begins to ring, it rings with a set, or superposition, of its natural frequencies — its modes of sonic energy dissipation. One could call these modes '' normal'' if the glass went on ringing forever. Here the amplitude of oscillation decays in time, so we call its modes ''quasi-normal''. To a high degree of accuracy, quasinormal ringing can be approximated by :\psi(t) \approx e^\cos\omega^t where \psi\left(t\right) is the amplitude of oscillation, \omega^ is the frequency, and \omega^ is the decay rate. The quasinormal frequency is described by two numbers, :\omega = \left(\omega^ , \omega^\right) or, more compactly :\psi\left(t\right) \approx \operatorname(e^) :\omega =\omega^ + i\omega^ Here, \mathbf is what is com ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Black Hole
A black hole is a massive, compact astronomical object so dense that its gravity prevents anything from escaping, even light. Albert Einstein's theory of general relativity predicts that a sufficiently compact mass will form a black hole. The boundary (topology), boundary of no escape is called the event horizon. A black hole has a great effect on the fate and circumstances of an object crossing it, but has no locally detectable features according to general relativity. In many ways, a black hole acts like an ideal black body, as it reflects no light. Quantum field theory in curved spacetime predicts that event horizons emit Hawking radiation, with thermal radiation, the same spectrum as a black body of a temperature inversely proportional to its mass. This temperature is of the Orders of magnitude (temperature), order of billionths of a kelvin for stellar black holes, making it essentially impossible to observe directly. Objects whose gravitational fields are too strong for ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Supersymmetry
Supersymmetry is a Theory, theoretical framework in physics that suggests the existence of a symmetry between Particle physics, particles with integer Spin (physics), spin (''bosons'') and particles with half-integer spin (''fermions''). It proposes that for every known particle, there exists a partner particle with different spin properties. There have been multiple experiments on supersymmetry that have failed to provide evidence that it exists in nature. If evidence is found, supersymmetry could help explain certain phenomena, such as the nature of dark matter and the hierarchy problem in particle physics. A supersymmetric theory is a theory in which the equations for force and the equations for matter are identical. In theoretical physics, theoretical and mathematical physics, any theory with this property has the ''principle of supersymmetry'' (SUSY). Dozens of supersymmetric theories exist. In theory, supersymmetry is a type of Spacetime symmetries, spacetime symmetry betwe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Gauge Theory
In physics, a gauge theory is a type of field theory in which the Lagrangian, and hence the dynamics of the system itself, does not change under local transformations according to certain smooth families of operations (Lie groups). Formally, the Lagrangian is invariant under these transformations. The term "gauge" refers to any specific mathematical formalism to regulate redundant degrees of freedom in the Lagrangian of a physical system. The transformations between possible gauges, called gauge transformations, form a Lie group—referred to as the '' symmetry group'' or the gauge group of the theory. Associated with any Lie group is the Lie algebra of group generators. For each group generator there necessarily arises a corresponding field (usually a vector field) called the gauge field. Gauge fields are included in the Lagrangian to ensure its invariance under the local group transformations (called gauge invariance). When such a theory is quantized, the quanta of th ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Twistor Theory
In theoretical physics, twistor theory was proposed by Roger Penrose in 1967 as a possible path to quantum gravity and has evolved into a widely studied branch of theoretical and mathematical physics. Penrose's idea was that twistor space should be the basic arena for physics from which space-time itself should emerge. It has led to powerful mathematical tools that have applications to differential and integral geometry, nonlinear differential equations and representation theory, and in physics to general relativity, quantum field theory, and the theory of scattering amplitudes. Twistor theory arose in the context of the rapidly expanding mathematical developments in Einstein's theory of general relativity in the late 1950s and in the 1960s and carries a number of influences from that period. In particular, Roger Penrose has credited Ivor Robinson as an important early influence in the development of twistor theory, through his construction of so-called ''Robinson congruences ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
AdS/CFT
In theoretical physics, the anti-de Sitter/conformal field theory correspondence (frequently abbreviated as AdS/CFT) is a conjectured relationship between two kinds of physical theories. On one side are anti-de Sitter spaces (AdS) that are used in theories of quantum gravity, formulated in terms of string theory or M-theory. On the other side of the correspondence are conformal field theories (CFT) that are quantum field theories, including theories similar to the Yang–Mills theories that describe elementary particles. The duality represents a major advance in the understanding of string theory and quantum gravity. This is because it provides a non-perturbative formulation of string theory with certain boundary conditions and because it is the most successful realization of the holographic principle, an idea in quantum gravity originally proposed by Gerard 't Hooft and promoted by Leonard Susskind. It also provides a powerful toolkit for studying strongly coupled quantum fie ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
New York Times
''The New York Times'' (''NYT'') is an American daily newspaper based in New York City. ''The New York Times'' covers domestic, national, and international news, and publishes opinion pieces, investigative reports, and reviews. As one of the longest-running newspapers in the United States, the ''Times'' serves as one of the country's Newspaper of record, newspapers of record. , ''The New York Times'' had 9.13 million total and 8.83 million online subscribers, both by significant margins the List of newspapers in the United States, highest numbers for any newspaper in the United States; the total also included 296,330 print subscribers, making the ''Times'' the second-largest newspaper by print circulation in the United States, following ''The Wall Street Journal'', also based in New York City. ''The New York Times'' is published by the New York Times Company; since 1896, the company has been chaired by the Ochs-Sulzberger family, whose current chairman and the paper's publ ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
James Glanz
James Glanz is an American journalist who was appointed as Baghdad bureau chief of ''The New York Times'' in 2007. Glanz joined the ''Times'' in 1999. Articles he wrote with Eric Lipton and others on the World Trade Center were chosen as a finalist for a Pulitzer Prize in explanatory journalism in 2002. Articles Lipton and Glanz wrote were also a part of the Nation Challenged package that won a Pulitzer for Public Service in 2002. He received three Gerald Loeb Awards – the 2020 Breaking News award for "Crash in Ethiopia," and two consecutive Visual Storytelling awards, first in 2021 for "Visualizing the Pandemic Economy" and again in 2022 for "Why the Mexico City Metro Collapsed". Glanz has a Ph.D. in astrophysical sciences from Princeton University Princeton University is a private university, private Ivy League research university in Princeton, New Jersey, United States. Founded in 1746 in Elizabeth, New Jersey, Elizabeth as the College of New Jersey, Princeton is ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
