Higgs boson

One possible signature of a Higgs boson from a simulated proton-proton collision. It decays almost immediately into two jets of hadrons and two electrons, visible as lines.
Composition	Elementary particle
Statistics	Bosonic
Status	Hypothetical
Symbol	H0
Theorized	F. Englert, R. Brout, P. Higgs, G. S. Guralnik, C. R. Hagen, and T. W. B. Kibble (1964)
Discovered	Not yet (as of December 2011[update]); searches ongoing at the LHC
Types	1, according to the Standard Model; 5 or more, according to supersymmetric models
Mass	likely 115–130 GeV/c2[1]
Spin	0

The Higgs boson is a hypothetical elementary particle predicted by the Standard Model (SM) of particle physics. It belongs to a class of particles known as bosons, characterized by an integer value of their spin quantum number. The Higgs field is a quantum field with a non-zero value that fills all of space, and explains why fundamental particles such as quarks and electrons have mass. The Higgs boson is an excitation of the Higgs field above its ground state.

The existence of the Higgs boson is predicted by the Standard Model to explain how spontaneous breaking of electroweak symmetry (the Higgs mechanism) takes place in nature, which in turn explains why other elementary particles have mass.^{[Note 1]} Its discovery would further validate the Standard Model as essentially correct, as it is the only elementary particle predicted by the Standard Model that has not yet been observed in particle physics experiments.^[2] The Standard Model completely fixes the properties of the Higgs boson, except for its mass. It is expected to have no spin and no electric or color charge, and it interacts with other particles through weak interaction and Yukawa interactions. Alternative sources of the Higgs mechanism that do not need the Higgs boson are also possible and would be considered if the existence of the Higgs boson were ruled out. They are known as Higgsless models.

Experiments to determine whether the Higgs boson exists are currently being performed using the Large Hadron Collider (LHC) at CERN, and were performed at Fermilab's Tevatron until its closure in late 2011. Mathematical consistency of the Standard Model requires that any mechanism capable of generating the masses of elementary particles become visible at energies above 1.4 TeV;^[3] therefore, the LHC (designed to collide two 7-TeV proton beams) is expected to be able to answer the question of whether or not the Higgs boson actually exists.^[4] In December 2011, Fabiola Gianotti and Guido Tonelli, spokespersons of the two main experiments at the LHC (ATLAS and CMS) both reported independently that their data hints at a possibility the Higgs may exist with a mass around 125 GeV/c² (about 133 proton masses, on the order of 10⁻²⁵ kg). They also reported that the original range under investigation has been narrowed down considerably and that a mass outside approximately 115–130 GeV/c² is almost ruled out.^[5] No conclusive answer yet exists, although it is expected that the LHC will provide sufficient data by the end of 2012 for a definite answer.^[1][6][7][8]

In the popular media, the particle is sometimes referred to as the God particle, a title generally disliked by the scientific community as media hyperbole that misleads readers.^[9]

History[link]

The six authors of the 1964 PRL papers, who received the 2010 J. J. Sakurai Prize for their work. From left to right: Kibble, Guralnik, Hagen, Englert, Brout. Right: Higgs.

Particle physicists believe matter to be made from fundamental particles whose interactions are mediated by exchange particles known as force carriers. At the start of the 1960s a number of these particles had been discovered or proposed, along with theories suggesting how they relate to each other. However these theories were known to be incomplete. One omission was that they could not explain the origins of mass as a property of matter. Goldstone's theorem, relating to continuous symmetries within some theories, also appeared to rule out many obvious solutions.^{[citation needed]}

The Higgs mechanism is a process by which vector bosons can get rest mass without explicitly breaking gauge invariance. The proposal for such a spontaneous symmetry breaking mechanism was originally suggested in 1962 by Philip Warren Anderson^[10] and developed into a full relativistic model in 1964 independently and almost simultaneously by three groups of physicists: by François Englert and Robert Brout;^[11] by Peter Higgs;^[12] and by Gerald Guralnik, C. R. Hagen, and Tom Kibble (GHK).^[13] Properties of the model were further considered by Guralnik in 1965^[14] and by Higgs in 1966.^[15] The papers showed that when a gauge theory is combined with an additional field which spontaneously breaks the symmetry group, the gauge bosons can consistently acquire a finite mass. In 1967, Steven Weinberg and Abdus Salam were the first to apply the Higgs mechanism to the breaking of the electroweak symmetry, and showed how a Higgs mechanism could be incorporated into Sheldon Glashow's electroweak theory,^[16][17][18] in what became the Standard Model of particle physics.

	Wikinews has news related to:
2010 Sakurai Prize awarded for 1964 Higgs Boson theory work Prospective Nobel Prize for Higgs boson work disputed

The three papers written in 1964 were each recognized as milestone papers during Physical Review Letters's 50th anniversary celebration.^[19] Their six authors were also awarded the 2010 J. J. Sakurai Prize for Theoretical Particle Physics for this work.^[20] (A dispute also arose the same year; in the event of a Nobel Prize up to 3 scientists would be eligible, with 6 authors credited for the papers.^[21] ) Two of the three PRL papers (by Higgs and by GHK) contained equations for the hypothetical field that would eventually become known as the Higgs field and its hypothetical quantum, the Higgs boson. Higgs' subsequent 1966 paper showed the decay mechanism of the boson; only a massive boson can decay and the decays can prove the mechanism.

In the paper by Higgs the boson is massive, and in a closing sentence Higgs writes that "an essential feature" of the theory "is the prediction of incomplete multiplets of scalar and vector bosons". In the paper by GHK the boson is massless and decoupled from the massive states. In reviews dated 2009 and 2011, Guralnik states that in the GHK model the boson is massless only in a lowest-order approximation, but it is not subject to any constraint and acquires mass at higher orders, and adds that the GHK paper was the only one to show that there are no massless Nambu-Goldstone bosons in the model and to give a complete analysis of the general Higgs mechanism.^[22][23]

In addition to explaining how mass is acquired by vector bosons, the Higgs mechanism also predicts the ratio between the W boson and Z boson masses as well as their couplings with each other and with the Standard Model quarks and leptons. Many of these predictions have subsequently been verified by precise measurements performed at the LEP and the SLC colliders, thus overwhelmingly confirming that some kind of Higgs mechanism does take place in nature,^[24] but the exact manner by which it happens is not yet proven. The results of searching for the Higgs boson are expected to provide evidence about how this is realized in nature.

Theoretical properties[link]

Summary of interactions between particles described by the Standard Model.

A one-loop Feynman diagram of the first-order correction to the Higgs mass. The Higgs boson couples strongly to the top quark so it might decay into top–anti-top quark pairs if it were heavy enough.

The Standard Model predicts the existence of a field (called the Higgs field) which has a non-zero amplitude in its ground state; i.e. a non-zero vacuum expectation value. The existence of this non-zero vacuum expectation spontaneously breaks electroweak gauge symmetry which in turn gives rise to the Higgs mechanism. It is the simplest process capable of giving mass to the gauge bosons while remaining compatible with gauge theories.^{[citation needed]} The field can be pictured as a pool of molasses that "sticks" to the otherwise massless fundamental particles that travel through the field, converting them into particles with mass that form (for example) the components of atoms. Its quantum would be a scalar boson, known as the Higgs boson.^{[citation needed]}

In the Standard Model, the Higgs field consists of two neutral and two charged component fields. Both of the charged components and one of the neutral fields are Goldstone bosons, which act as the longitudinal third-polarization components of the massive W⁺, W^–, and Z bosons.^{[citation needed]} The quantum of the remaining neutral component corresponds to (and is theoretically realized as) the massive Higgs boson. Since the Higgs field is a scalar field, the Higgs boson has no spin. The Higgs boson is also its own antiparticle and is CP-even, and has zero electric and colour charge.^{[citation needed]}

The Standard Model does not predict the mass of the Higgs boson.^{[citation needed]} If that mass is between 115 and 180 GeV/c², then the Standard Model can be valid at energy scales all the way up to the Planck scale (10¹⁶ TeV).^{[citation needed]} Many theorists expect new physics beyond the Standard Model to emerge at the TeV-scale, based on unsatisfactory properties of the Standard Model.^{[citation needed]} The highest possible mass scale allowed for the Higgs boson (or some other electroweak symmetry breaking mechanism) is 1.4 TeV; beyond this point, the Standard Model becomes inconsistent without such a mechanism, because unitarity is violated in certain scattering processes.^{[citation needed]}

In theory the mass of the Higgs boson can be estimated indirectly. In the Standard Model, the Higgs boson has a number of indirect effects; most notably, Higgs loops result in tiny corrections to masses of W and Z bosons. Precision measurements of electroweak parameters, such as the Fermi constant and masses of W/Z bosons, can be used to constrain the mass of the Higgs. As of July 2011, the precision electroweak measurements tell us that the mass of the Higgs boson is lower than about 161 GeV/c² at 95% confidence level (CL). This upper bound increases to 185 GeV/c² when including the LEP-2 direct search lower bound of 114.4 GeV/c².^[24] These indirect constraints rely on the assumption that the Standard Model is correct. It may still be possible to discover a Higgs boson above 185 GeV/c² if it is accompanied by other particles beyond those predicted by the Standard Model.^{[citation needed]}

Extensions to the Standard Model including supersymmetry (SUSY) predict the existence of families of Higgs bosons, rather than the one Higgs particle of the Standard Model. Among the SUSY models, in the Minimal Supersymmetric Standard Model (MSSM) the Higgs mechanism yields the smallest number of Higgs bosons; there are two Higgs doublets, leading to the existence of a quintet of scalar particles: two CP-even neutral Higgs bosons h⁰ and H⁰, a CP-odd neutral Higgs boson A⁰, and two charged Higgs particles H^±. Many supersymmetric models predict that the lightest Higgs boson will have a mass only slightly above the current experimental limits, at around 120 GeV/c² or less.^{[citation needed]}

Alternative mechanisms for electroweak symmetry breaking[link]

In the years since the Higgs field and boson were proposed, several alternative models have been proposed by which the Higgs mechanism might be realized. The Higgs boson exists in some but not all theories. For example, it exists in the Standard Model and extensions such as the Minimal Supersymmetric Standard Model yet is not expected to exist in alternative models such as Technicolor. Models which do not include a Higgs field or a Higgs boson are known as Higgsless models. In these models, strongly interacting dynamics rather than an additional (Higgs) field produce the non-zero vacuum expectation value that breaks electroweak symmetry. A partial list of these alternative mechanisms are:

• Technicolor,^[25] a class of models that attempts to mimic the dynamics of the strong force as a way of breaking electroweak symmetry.
• Extra dimensional Higgsless models where the role of the Higgs field is played by the fifth component of the gauge field.^[26]
• Abbott-Farhi models of composite W and Z vector bosons.^[27]
• Top quark condensate theory in which a fundamental scalar Higgs field is replaced by a composite field composed of the top quark and its antiquark.
• The braid model of Standard Model particles by Sundance Bilson-Thompson, compatible with loop quantum gravity and similar theories.^[28]

A goal of the LHC and Tevatron experiments is to distinguish between these models and determine if the Higgs boson exists or not.

Experimental search[link]

Status as of March 2011.^{[citation needed]} Colored sections have been ruled out to the stated confidence intervals either by indirect measurements and LEP experiments (green) or by Tevatron experiments (orange).

Feynman diagrams showing two ways the Higgs boson might be produced at the LHC. Left: two gluons convert to top/anti-top quark pairs, which combine. Right: two quarks emit W or Z bosons, which combine.

Wikimedia Commons has media related to: Large Hadron Collider

As of December 2011^[update], the Higgs boson has yet to be confirmed experimentally,^[29] despite large efforts invested in accelerator experiments at CERN and Fermilab, and media reports of possible evidence.^[30][31][32]

Like other massive particles (e.g. the top quark and W and Z bosons), Higgs bosons created in particle accelerators decay long before they reach any of the detectors. However, the Standard Model precisely predicts the possible modes of decay and their probabilities. This allows events in which a Higgs was created to be identified by examining the decay products.

Prior to the year 2000, the data gathered at the Large Electron–Positron Collider (LEP) at CERN allowed an experimental lower bound to be set for the mass of the Standard Model Higgs boson of 114.4 GeV/c² at the 95% confidence level (CL). The same experiment has produced a small number of events that could be interpreted as resulting from Higgs bosons with a mass just above this cut off — around 115 GeV — but the number of events was insufficient to draw definite conclusions.^[33] The LEP was shut down in 2000 due to construction of its successor, the Large Hadron Collider (LHC).

Full operation at the LHC was delayed for 14 months from its initial successful tests on 10 September 2008, until mid-November 2009,^[34][35] following a magnet quench event 9 days after its inaugural tests that damaged over 50 superconducting magnets and contaminated the vacuum system.^[36] The quench was traced to a faulty electrical connection and repairs took several months;^[37][38] electrical fault detection and rapid quench-handling systems were also upgraded.

At the Fermilab Tevatron, there were also ongoing experiments searching for the Higgs boson. As of July 2010^[update], combined data from CDF and DØ experiments at the Tevatron were sufficient to exclude the Higgs boson in the range 158-175 GeV/c² at 95% CL.^[39][40] Preliminary results as of July 2011 extended the excluded region to the range 156-177 GeV/c² at 95% CL.^[41]

Data collection and analysis in search of Higgs intensified from 30 March 2010 when the LHC began operating at 3.5 TeV.^[42] Preliminary results from the ATLAS and CMS experiments at the LHC as of July 2011 exclude a Standard Model Higgs boson in the mass range 155-190 GeV/c^2[43] and 149-206 GeV/c²,^[44] respectively, at 95% CL. All of the above confidence intervals were derived using the CLs method.

As of December 2011 the search has narrowed to the approximate region 115–130 GeV with a specific focus around 125 GeV where both the ATLAS and CMS experiments independently report an excess of events,^{[1][7][45][46]} meaning that a higher than expected number of particle patterns compatible with the decay of a Higgs boson were detected in this energy range. The data is not yet sufficient to show whether or not these excesses are due to background fluctuations (i.e. random chance or other causes), and its statistical significance is not large enough to draw conclusions yet or even formally to count as an "observation", but the fact that the two independent experiments have shown excesses at around the same mass has led to considerable excitement in the particle physics community.^[47]

On 22 December 2011, the DØ Collaboration also reported limitations on the Higgs boson within the Minimal Supersymmetric Standard Model, an extension to the Standard Model. Proton-antiproton (pp) collisions with a centre-of-mass energy of 1.96 TeV had allowed them to set an upper limit for Higgs boson production within MSSM ranging from 90 to 300 GeV, and excluding tanβ > 20–30 for masses of the Higgs boson below 180 GeV (tanβ is the ratio of the two Higgs doublet vacuum expectation values).^[48]

On 7 March 2012, the DØ and CDF Collaborations announced that, after analyzing the full data set from the Tevatron accelerator, they found excesses in their data that might be interpreted as coming from a Higgs boson with a mass in the region of 115 to 135 GeV/c². The significance of the excesses is quantified as 2.2 standard deviations, not enough to rule out that they are due to a statistical fluctuation. This new result also extends the range of Higgs-mass values excluded by the Tevatron experiments at 95% CL, which becomes 147-179 GeV/c².^[49][50]

It is expected that the LHC will provide sufficient data to either exclude or confirm the existence of the Standard Model Higgs boson by the end of 2012.^[51]

Timeline of experimental evidence[link]

All results refer to the Standard Model Higgs boson, unless otherwise stated.

• Prior to 2000 – Large Electron–Positron Collider experiments set a lower bound for the Higgs boson of 114.4 GeV/c² at the 95% confidence level (CL), with a small number of events around 115 GeV.^[33]
• July 2010 – data from CDF (Fermilab) and DØ (Tevatron) experiments exclude the Higgs boson in the range 158–175 GeV/c² at 95% CL.^[39][40]
• 24 April 2011 – media reports 'rumors' of a find;^[52] these were debunked by May 2011.^[53] They had not been a hoax, but were based on unofficial, unreviewed results.^[54]
• 24 July 2011 – the LHC reported possible signs of the particle, the ATLAS Note concluding: "In the low mass range (c. 120–140 GeV) an excess of events with a significance of approximately 2.8 sigma above the background expectation is observed" and the BBC reporting that "interesting particle events at a mass of between 140 and 145 GeV" were found.^[55][56] These findings were repeated shortly thereafter by researchers at the Tevatron with a spokesman stating that: "There are some intriguing things going on around a mass of 140GeV."^[55] On 22 August 2011 it was reported that these anomalous results had become insignificant on the inclusion of more data from ATLAS and CMS and that the non-existence of the particle had been confirmed by LHC collisions to 95% certainty between 145–466 GeV (except for a few small islands around 250 GeV).^[57]
• 23–24 July 2011 – Preliminary LHC results exclude the ranges 155–190 GeV/c² (ATLAS)^[43] and 149–206 GeV/c² (CMS)^[44] at 95% CL.
• 27 July 2011 – preliminary CDF/DØ results extend the excluded range to 156–177 GeV/c² at 95% CL.^[41]
• 18 November 2011 – a combined analysis of ATLAS and CMS data further narrowed the window for the allowed values of the Higgs boson mass to 114–141 GeV.^[58]
• 13 December 2011 – experimental results were announced from the ATLAS and CMS experiments, indicating that if the Higgs boson exists, its mass is limited to the range 116–130 GeV (ATLAS) or 115–127 GeV (CMS), with other masses excluded at 95% CL. Observed excesses of events at around 124 GeV (CMS) and 125–126 GeV (ATLAS) are consistent with the presence of a Higgs boson signal, but also consistent with fluctuations in the background. The global statistical significances of the excesses are 1.9 sigma (CMS) and 2.6 sigma (ATLAS) after correction for the look elsewhere effect.^[1][7] As of 13 December 2011, a combined result is not yet available.
• 22 December 2011 – the DØ Collaboration also sets limits on Higgs boson masses within the Minimal Supersymmetric Standard Model (an extension of the Standard Model), with an upper limit for production ranging from 90 to 300 GeV, and excluding tanβ>20–30 for Higgs boson masses below 180 GeV at 95% CL.^[48]
• 7 March 2012 – the DØ and CDF Collaborations announced that they found excesses that might be interpreted as coming from a Higgs boson with a mass in the region of 115 to 135 GeV/c² in the full sample of data from Tevatron. The significance of the excesses is quantified as 2.2 standard deviations, corresponding to a 1 in 250 probability of being due to a statistical fluctuation. This is a lower significance, but consistent with and independent of the ATLAS and CMS data at the LHC.^[59][60]

"The God particle"[link]

The Higgs boson is often referred to as "the God particle" by the media,^[61] after the title of Leon Lederman's popular science book on particle physics, The God Particle: If the Universe Is the Answer, What Is the Question?^[62][63] While use of this term may have contributed to increased media interest,^[63] many scientists dislike it, since it overstates the particle's importance, not least since its discovery would still leave unanswered questions about the unification of Quantum chromodynamics, the electroweak interaction and gravity, and the ultimate origin of the universe.^[61]

Lederman said he gave it the nickname "The God Particle" because the particle is "so central to the state of physics today, so crucial to our understanding of the structure of matter, yet so elusive,"^[61][62][64] but jokingly added that a second reason was because "the publisher wouldn't let us call it the Goddamn Particle, though that might be a more appropriate title, given its villainous nature and the expense it is causing."^[62]

A renaming competition conducted by the science correspondent for the British Guardian newspaper chose the name "the champagne bottle boson" as the best from among their submissions: "The bottom of a champagne bottle is in the shape of the Higgs potential and is often used as an illustration in physics lectures. So it's not an embarrassingly grandiose name, it is memorable, and [it] has some physics connection too."^[65]

See also[link]

	Book: Particles of the Standard Model
Wikipedia books are collections of articles that can be downloaded or ordered in print.

• Bose–Einstein statistics
• Boson
• Dalitz plot
• Goldstone boson
• Higgs boson in fiction
• Higgs mechanism
• Large Hadron Collider (LHC)
• List of particles
• Quantum triviality
• Yukawa interaction
• ZZ diboson

Notes[link]

1. ^ Only 1% of the mass of composite particles, such as the proton and neutron, is due to the Higgs mechanism. The other 99% is due to the strong interaction.

References[link]

Further reading[link]

External links[link]

Wikimedia Commons has media related to: Higgs boson

• Hunting the Higgs boson at C.M.S. Experiment, at CERN
• The Higgs boson" by the CERN exploratorium.
• Particle Data Group: Review of searches for Higgs bosons.
• The Atom Smashers, a documentary film about the search for the Higgs boson at Fermilab.
• 2001, a spacetime odyssey: proceedings of the Inaugural Conference of the Michigan Center for Theoretical Physics : Michigan, USA, 21–25 May 2001, (p.86 – 88), ed. Michael J. Duff, James T. Liu, ISBN 978-981-238-231-3, containing Higgs' story of the Higgs Boson.
• Why the HIggs particle is so important!

Leonard Susskind
Leonard Susskind
Born	1940 South Bronx, New York City, USA
Residence	United States
Citizenship	United States
Nationality	American
Fields	Physics, Mathematics
Institutions	Yeshiva University University of Tel Aviv Stanford University Korea Institute for Advanced Study Perimeter Institute for Theoretical Physics
Alma mater	City College of New York Cornell University
Doctoral advisor	Peter A. Carruthers
Known for	Holographic principle String theory landscape Quark confinement Hamiltonian lattice gauge theory
Notable awards	American Institute of Physics' Science Writing Award Sakurai Prize (1998) Boris Pregel Award, New York Academy of Science (1975)[1]

Leonard Susskind (born 1940)^[2] is the Felix Bloch Professor of Theoretical Physics at Stanford University. His research interests include string theory, quantum field theory, quantum statistical mechanics and quantum cosmology.^[1] He is a member of the National Academy of Sciences,^[3] and the American Academy of Arts and Sciences,^[4] an associate member of the faculty of Canada's Perimeter Institute for Theoretical Physics,^[5] and a distinguished professor of the Korea Institute for Advanced Study.^[6]

Susskind is widely regarded as one of the fathers of string theory,^[7] having, with Yoichiro Nambu and Holger Bech Nielsen, independently introduced the idea that particles could in fact be states of excitation of a relativistic string.^[8] He was the first to introduce the idea of the string theory landscape in 2003.^[9]

In 1997, Susskind was awarded the J.J. Sakurai Prize for his "pioneering contributions to hadronic string models, lattice gauge theories, quantum chromodynamics, and dynamical symmetry breaking." Susskind's hallmark, according to colleagues, has been the application of "brilliant imagination and originality to the theoretical study of the nature of the elementary particles and forces that make up the physical world."^[10]

Early life and education[link]

Susskind was born to a poor Jewish family from the South Bronx section of New York City,^[11] and now resides in Palo Alto, California. He began working as a plumber at the age of 16, taking over for his father who had become ill.^[11] Later, he enrolled in the City College of New York as an engineering student, graduating with a B.S. in physics in 1962.^[4] In an interview in the Los Angeles Times, Susskind recalls the moment he discussed with his father this change in career path: "When I told my father I wanted to be a physicist, he said, ‘Hell no, you ain’t going to work in a drug store.’ I said no, not a pharmacist. I said, ‘Like Einstein.’ He poked me in the chest with a piece of plumbing pipe. ‘You ain’t going to be no engineer,’ he said. ‘You’re going to be Einstein.’"^[11] Susskind then studied at Cornell University under Peter A. Carruthers where he earned his Ph.D. in 1965. He has been married twice, first in 1960,^[4] and has four children.

Career[link]

Susskind was an Assistant Professor of Physics, then an Associate Professor at Yeshiva University (1966–1970), after which he went for a year at the University of Tel Aviv (1971–72), returning to Yeshiva to become a Professor of Physics (1970–1979). Since 1979 he has been Professor of Physics at Stanford University,^[12] and since 2000 has held the Felix Bloch Professorship of Physics.

In 2007, Susskind joined the Faculty of Perimeter Institute for Theoretical Physics in Waterloo, Ontario, Canada, as an Associate Member. He has been elected to the National Academy of Sciences and the American Academy of Arts and Sciences, and was awarded the 1998 Sakurai Prize for theoretical physics. He is also a distinguished professor at Korea Institute for Advanced Study.^[13]

Scientific career[link]

Susskind was one of at least three physicists who independently discovered during or around 1970 that the Veneziano dual resonance model of strong interactions could be described by a quantum mechanical model of strings,^[14] and was the first to propose the idea of the string theory landscape. Susskind has also made contributions in the following areas of physics:

• The independent discovery of the string theory model of particle physics
• The theory of quark confinement^[15]
• The development of Hamiltonian lattice gauge theory^[16]
• The theory of scaling violations in deep inelastic electroproduction
• The theory of symmetry breaking sometimes known as "technicolor theory"^[17]
• The second, yet independent, theory of cosmological baryogenesis^[18] (Sakharov's work was first, but was mostly unknown in the Western hemisphere.)
• String theory of black hole entropy^[19]
• The principle of black hole complementarity^[20]
• The causal patch hypothesis
• The holographic principle^[21]
• M-theory, including development of the BFSS matrix model ^[22]
• Kogut-Susskind fermions
• Introduction of holographic entropy bounds in physical cosmology
• The idea of an anthropic string theory landscape^[23]
• The Census Taker's Hat

Development of String Theory[link]

The story goes that "In 1970, a young physicist named Leonard Susskind got stuck in an elevator with Murray Gell-Mann, one of physics' top theoreticians, who asked him what he was working on. Susskind said he was working on a theory that represented particles 'as some kind of elastic string, like a rubber band.' Gell-Mann responded with loud, derisive laughter."^[24]

Books[link]

Susskind is the author of two popular science books, The Cosmic Landscape: String Theory and the Illusion of Intelligent Design^[25] published in 2005, and The Black Hole War: My battle with Stephen Hawking to make the world safe for quantum mechanics^[26] published in 2008.

The Cosmic Landscape[link]

The Cosmic Landscape: String Theory and the Illusion of Intelligent Design is Susskind's first popular science book, published by Little, Brown and Company on December 12, 2005.^[25] It is Susskind's attempt to bring his idea of the anthropic landscape of string theory to the general public. In the book, Susskind describes how the string theory landscape was an almost inevitable consequence of several factors, one of which was Steven Weinberg's prediction of the cosmological constant in 1987. The question addressed here is why our universe is fine-tuned for our existence. Susskind explains that Weinberg calculated that if the cosmological constant was just a little different, our universe would cease to exist.

The Black Hole War[link]

The Black Hole War: My Battle with Stephen Hawking to Make the World Safe for Quantum Mechanics is Susskind's second popular science book, published by Little, Brown, and Company on July 7, 2008.^[26] The book is his most famous work and explains what he thinks would happen to the information and matter stored in a black hole when it evaporates. The book sparked from a debate that started in 1981, when there was a meeting of physicists to try to decode some of the mysteries about how particles of particular elemental compounds function. During this discussion Stephen Hawking stated that the information inside a black hole is lost forever as the black hole evaporates. It took 28 years for Leonard Susskind to formulate his theory that would prove Hawking wrong. He then published his theory in his book, The Black Hole War. Like The Cosmic Landscape, The Black Hole War is aimed at the lay reader. He writes: "The real tools for understanding the quantum universe are abstract mathematics: infinite dimensional Hilbert spaces, projection operators, unitary matrices and a lot of other advanced principles that take a few years to learn. But let's see how we do in just a few pages."

Lectures[link]

An entire series of courses of lectures on essential theoretical foundations of modern physics by Susskind is available on the iTunes platform from "Stanford on iTunes U" and YouTube from "Stanford University's Channel". These lectures are intended for the general public as well as students. The following courses are available:

Modern Physics: The Theoretical Minimum[link]

Core Sequence[link]

1. Classical Mechanics (Fall 2007) iTunes YouTube
2. Quantum Mechanics (Winter 2008) iTunes YouTube
3. Special Relativity and Classical Field Theory (Spring 2008) iTunes YouTube
4. Einstein's General Theory of Relativity (Fall 2008) iTunes YouTube
5. Cosmology (Winter 2009) iTunes YouTube
6. Statistical Mechanics (Spring 2009) iTunes YouTube

Core Sequence Repeated (In Progress)[link]

1. Classical Mechanics (Fall 2011) iTunes YouTube
2. Quantum Mechanics (Winter 2012) iTunes YouTube
3. Special Relativity and Classical Field Theory (Spring 2012 - in Progress) iTunes YouTube

Other Lectures[link]

• Particle Physics: 1 Basic Concepts (Fall 2009) iTunes YouTube
• Particle Physics: 2 Standard Model (Winter 2010) iTunes YouTube
• Particle Physics: 3 Supersymmetry, Grand Unification, String Theory (Spring 2010) iTunes
• String Theory and M-Theory (Fall 2010) iTunes YouTube
• Topics in String Theory (Winter 2011) iTunes YouTube

A separate series of lectures on Quantum Mechanics and Special Relativity[link]

• Quantum Entanglements Part 1 (Fall 2006) iTunes YouTube
• Quantum Entanglements Part 2 (Not available online)
• Quantum Entanglements Part 3 (Spring 2007) iTunes YouTube

(Note that some of the lecture names are a little mixed-up: "Quantum Entanglements Part 3" is in fact a lecture series on special relativity and electromagnetic theory, and the order in which the lectures were given is 1, 4, 5, 6, 7, 2&3, 8 and 9 (in terms of the numbers given on the videos). There is no mention of string theory in the series "Supersymmetry, Grand Unification, String Theory", nor of M-theory in "String Theory and M-Theory")

Smolin-Susskind Debate[link]

The Smolin-Susskind debate refers to the series of intense postings in 2004 between Lee Smolin and Susskind, concerning Smolin’s argument that the "Anthropic Principle cannot yield any falsifiable predictions, and therefore cannot be a part of science."^[27] It began on July 26, 2004, with Smolin's publication of "Scientific alternatives to the anthropic principle". Smolin e-mailed Susskind asking for a comment. Having not had the chance to read the paper, Susskind requested a summarization of his arguments. Smolin obliged, and on July 28, 2004, Susskind responded, saying that the logic Smolin followed "can lead to ridiculous conclusions".^[27] The next day, Smolin responded, saying that "If a large body of our colleagues feels comfortable believing a theory that cannot be proved wrong, then the progress of science could get stuck, leading to a situation in which false, but unfalsifiable theories dominate the attention of our field." This was followed by another paper by Susskind which made a few comments about Smolin's theory of "cosmic natural selection".^[28] The Smolin-Susskind debate finally ended with each of them agreeing to write a final letter which would be posted on Edge, with three conditions attached: (1) No more than one letter each; (2) Neither sees the other's letter in advance; (3) No changes after the fact.

See also[link]

• Superstring theory
• Quantum chromodynamics
• Supersymmetry
• Susskind-Glogower operator
• List of theoretical physicists
• Kogut-Susskind fermions
• Fischler-Susskind mechanism
• Boris Pregel

References[link]

Further reading[link]

• Chown, Marcus, "Our world may be a giant hologram", New Scientist, 15 January 2009, magazine issue 2691. "The holograms you find on credit cards and banknotes are etched on two-dimensional plastic films. When light bounces off them, it recreates the appearance of a 3D image. In the 1990s physicists Leonard Susskind and Nobel prizewinner Gerard 't Hooft suggested that the same principle might apply to the universe as a whole. Our everyday experience might itself be a holographic projection of physical processes that take place on a distant, 2D surface."

External links[link]

Wikiquote has a collection of quotations related to: Leonard Susskind

• Leonard Susskind's Homepage (Stanford University)
• Susskind's Blog: Physics for Everyone
• The Edge:
  • "Interview with Leonard Susskind."
  • "Smolin vs. Susskind: The Anthropic Principle" Susskind and Lee Smolin debate the Anthropic principle
• Radio Interview from This Week in Science March 14, 2006 Broadcast
• "Father of String Theory Muses on the Megaverse": Podcast.
• Leonard Susskind at the Internet Movie Database
• The Cosmic Landscape book discussion at The Commonwealth Club, February 2007
• The Black Hole War speaks on black hole conflict at The Commonwealth Club, July 2008
• Leonard Susskind: My friend Richard Feynman - A Ted talk

Nick Cave
Nick Cave at an event in New York City, 2009
Background information
Born	(1957-09-22) 22 September 1957 (age 54) Warracknabeal, Victoria, Australia
Genres	Post-punk, gothic rock,[1][2] alternative rock, garage rock
Occupations	Singer-songwriter, multi-instrumentalist, writer, actor, composer
Instruments	Guitar, piano, keyboards, vocals
Years active	1973–present
Labels	Mute
Associated acts	Boys Next Door, Nick Cave and the Bad Seeds, Grinderman, The Birthday Party

Nicholas Edward "Nick" Cave (born 22 September 1957) is an Australian musician, songwriter, author, screenwriter, composer and occasional film actor.

He is best known for his work as a frontman of the critically acclaimed rock band Nick Cave and the Bad Seeds, established in 1983, a group known for its eclectic influences and musical styles. Before that, he had fronted the group The Birthday Party in the early 1980s, a band renowned for its highly gothic,^[1][2] challenging lyrics and violent sound influenced by free jazz, blues, and post-punk. In 2006, he formed the garage rock band Grinderman that released its debut the following year. Cave's music is generally characterised by emotional intensity, a wide variety of influences and lyrical obsessions with religion, death, love and violence.^[3]

Upon Cave's induction into the ARIA Hall of Fame, ARIA Awards committee chairman Ed St John said, “Nick Cave has enjoyed—and continues to enjoy—one of the most extraordinary careers in the annals of popular music. He is an Australian artist like Sidney Nolan is an Australian artist—beyond comparison, beyond genre, beyond dispute."^[4]

Youth, education and family[link]

Cave was born in the small town of Warracknabeal in the state of Victoria, Australia, to Dawn Cave (née Treadwell) and Colin Frank Cave. He has two brothers: Tim (b. 1952) and Peter (b. 1954), and a sister, Julie (b. 1959). As a child, he lived in Warracknabeal and then Wangaratta in rural Victoria. His father was an English teacher and administrator, with a love of literature, and his mother was a librarian. Cave's paternal grandfather's surname was originally Landvoigt, he later in his life became known as Frank Jason Cave.^[5][6][7][8]