For other meanings, see Boson (disambiguation).

The Standard Model of elementary particles, with the gauge bosons in the last column

In particle physics, bosons are one of the two fundamental classes of subatomic particles, the other being fermions. Bosons are characterized by their obedience to Bose–Einstein statistics. This class of particles includes photons and gluons, as well as the hypothetical Higgs boson.

The word boson derives from the name of the Indian physicist Satyendra Nath Bose.^[1]

Properties of bosons[link]

Bosons contrast with fermions, which obey Fermi–Dirac statistics. Two or more fermions cannot occupy the same quantum state.

Since bosons with the same energy can occupy the same place in space, bosons are often force carrier particles. In contrast, fermions are usually associated with matter (although in quantum physics the distinction between the two concepts is not clear cut).

Bosons may be either elementary, like photons, or composite, like mesons.

All observed bosons have integer spin, as opposed to fermions, which have half-integer spin. This is in accordance with the spin-statistics theorem, which states that in any reasonable relativistic quantum field theory, particles with integer spin are bosons, while particles with half-integer spin are fermions.

While most bosons are composite particles, in the Standard Model, there are six bosons which are elementary:

• the four gauge bosons (γ · g · W±
  · Z)
• the Higgs boson (H0
  )
• the graviton (G).

Unlike the gauge bosons, the Higgs boson and graviton have not yet been observed experimentally.^[2]

Composite bosons are important in superfluidity and other applications of Bose–Einstein condensates.

Definition and basic properties[link]

By definition, bosons are particles which obey Bose–Einstein statistics: when one swaps two bosons, the wavefunction of the system is unchanged.^[3] Fermions, on the other hand, obey Fermi–Dirac statistics and the Pauli exclusion principle: two fermions cannot occupy the same quantum state, resulting in a "rigidity" or "stiffness" of matter which includes fermions. Thus fermions are sometimes said to be the constituents of matter, while bosons are said to be the particles that transmit interactions (force carriers), or the constituents of radiation. The quantum fields of bosons are bosonic fields, obeying canonical commutation relations.

The properties of lasers and masers, superfluid helium-4 and Bose–Einstein condensates are all consequences of statistics of bosons. Another result is that the spectrum of a photon gas in thermal equilibrium is a Planck spectrum, one example of which is black-body radiation; another is the thermal radiation of the opaque early Universe seen today as microwave background radiation. Interactions between elementary particles are called fundamental interactions. The fundamental interactions of virtual bosons with real particles result in all forces we know.

All known elementary and composite particles are bosons or fermions, depending on their spin: particles with half-integer spin are fermions; particles with integer spin are bosons. In the framework of nonrelativistic quantum mechanics, this is a purely empirical observation. However, in relativistic quantum field theory, the spin-statistics theorem shows that half-integer spin particles cannot be bosons and integer spin particles cannot be fermions.^[4]

In large systems, the difference between bosonic and fermionic statistics is only apparent at large densities—when their wave functions overlap. At low densities, both types of statistics are well approximated by Maxwell-Boltzmann statistics, which is described by classical mechanics.

Elementary bosons[link]

All observed elementary particles are either fermions or bosons. The observed elementary bosons are all gauge bosons: photons, W and Z bosons and gluons.

• Photons are the force carriers of the electromagnetic field.
• W and Z bosons are the force carriers which mediate the weak force.
• Gluons are the fundamental force carriers underlying the strong force.

In addition, the standard model postulates the existence of Higgs bosons, which give other particles their mass via the Higgs mechanism.

Finally, many approaches to quantum gravity postulate a force carrier for gravity, the graviton, which is a boson of spin 2.

Composite bosons[link]

Composite particles (such as hadrons, nuclei, and atoms) can be bosons or fermions depending on their constituents. More precisely, because of the relation between spin and statistics, a particle containing an even number of fermions is a boson, since it has integer spin.

Examples include the following:

• Any meson, since mesons contain one quark and one antiquark
• The nucleus of a carbon-12 atom, which contains 6 protons and 6 neutrons
• The helium-4 atom, consisting of 2 protons, 2 neutrons and 2 electrons.

The number of bosons within a composite particle made up of simple particles bound with a potential has no effect on whether it is a boson or a fermion.

Fermionic or bosonic behavior of a composite particle (or system) is only seen at large (compared to size of the system) distance. At proximity, where spatial structure begins to be important, a composite particle (or system) behaves according to its constituent makeup. For example, two atoms of helium-4 cannot share the same space if it is comparable in size to that of the inner structure of the helium atom itself (~10⁻¹⁰ m)—despite bosonic properties of the helium-4 atoms. Thus, liquid helium has finite density comparable to the density of ordinary liquid matter.

See also[link]

• Anyon
• Bose gas
• Bosonic field
• Fermion
• Identical particles
• Parastatistics
• Satyendra Nath Bose
• Superfluid

Notes[link]

References[link]

• Sakurai, J.J. (1994). Modern Quantum Mechanics (Revised Edition), pp 361–363. Addison-Wesley Publishing Company, ISBN 0-201-53929-2.
• Srednicki, Mark (2007). Quantum Field Theory, Cambridge University Press, ISBN 978-0-521-86449-7.

This article contains Japanese text. Without proper rendering support, you may see question marks, boxes, or other symbols instead of kanji and kana.

Michio Kaku (加来 道雄, Kaku Michio^?, born January 24, 1947) is an American theoretical physicist, the Henry Semat Professor of Theoretical Physics in the City College of New York of City University of New York, a co-founder of string field theory,^[1] a futurist, and a "communicator" and "popularizer" of science. He has written several books about physics and related topics; he has made frequent appearances on radio, television, and film; and he writes extensive online blogs and articles. He has written two New York Times best sellers, Physics of the Impossible (2008) and Physics of the Future (2011). He has hosted several TV specials for BBC-TV, the Discovery Channel, and the Science Channel.

Early life and education[link]

Kaku was born in San Jose, California to Japanese immigrant parents. His grandfather came to the United States to take part in the clean-up operation after the 1906 San Francisco Earthquake^{[citation needed]}. His father was born in California but was educated in Japan and spoke little English. Both his parents were put in the Tule Lake War Relocation Center, where they met and where his two brothers were born.

At Cubberley High School in Palo Alto, Kaku assembled an atom smasher in his parents' garage for a science fair project.^[2] At the National Science Fair in Albuquerque, New Mexico, he attracted the attention of physicist Edward Teller, who took Kaku as a protégé, awarding him the Hertz Engineering Scholarship. Kaku graduated summa cum laude from Harvard University in 1968 and was first in his physics class. He attended the Berkeley Radiation Laboratory at the University of California, Berkeley and received a Ph.D. in 1972, and in 1972 he held a lectureship at Princeton University.

During the Vietnam War, Kaku completed his U.S. Army basic training at Fort Benning, Georgia and his advanced individual training at Fort Lewis, Washington.^[3] However, the Vietnam War ended before he was deployed as an infantryman.

Academic career[link]

Kaku became a visiting professor at the Institute for Advanced Study in Princeton,^[4] and New York University.^[5] He currently holds the Henry Semat Chair and Professorship in theoretical physics at the City College of New York.^[6]

Kaku has had over 70 articles published in physics journals such as Physical Review, covering topics such as superstring theory, supergravity, supersymmetry, and hadronic physics.^[7] In 1974, along with Prof. Keiji Kikkawa of Osaka University, he authored the first papers describing string theory in a field form.^[8][9]

Kaku is the author of several textbooks on string theory and quantum field theory.

Popular science[link]

Kaku is most widely known as a popularizer of science.^[10] He has written books and appeared on many television programs as well as film. He also hosts a weekly radio program.

Books[link]

Kaku is the author of various popular science books.

• Hyperspace (1994)
• Beyond Einstein (with Jennifer Thompson) (1995)
• Visions: How Science Will Revolutionize the 21st Century^[11] (1998)
• Einstein's Cosmos (2004)
• Parallel Worlds (2004)
• Physics of the Impossible (2008)
• Physics of the Future (2011)

Hyperspace was a best-seller and was voted one of the best science books of the year by both The New York Times^[10] and The Washington Post. Parallel Worlds was a finalist for the Samuel Johnson Prize for non-fiction in the UK.^[12]

Radio[link]

Kaku is the host of the weekly, one-hour radio program Explorations, produced by the Pacifica Foundation's WBAI in New York. "Explorations" is syndicated to community and independent radio stations and makes previous broadcasts available on the program's website. Kaku defines the show as dealing with the general topics of science, war, peace, and the environment.

In April 2006, Kaku began broadcasting Science Fantastic on 90 commercial radio stations, the only nationally syndicated science program on commercial radio in the United States. It is syndicated by Talk Radio Network and now reaches 130 radio stations and America's Talk on XM. The program is formatted as a live listener call-in show, focusing on "futurology," which he defines as the future of science.^{[citation needed]} Featured guests include Nobel laureates and top researchers on the topics of string theory, time travel, black holes, gene therapy, aging, space travel, artificial intelligence, and SETI. When Kaku is busy filming for television, Science Fantastic goes on hiatus, sometimes for several months. Kaku is also a frequent guest on many programs, where he is outspoken in all areas and issues he considers of importance, such as the program Coast to Coast AM, where on 30 November 2007, he reaffirmed his belief that there is a 100% probability of extraterrestrial life in the universe.^[13]

Kaku has appeared on The Opie and Anthony Show a number of times, discussing popular fiction such as Back to The Future, Lost, and the theories behind time-travel that these and other fictional entertainment focus on.

Television and film[link]

Kaku has appeared in many forms of media and on many programs and networks, including Good Morning America, The Screen Savers, Larry King Live, 60 Minutes, Nightline, 20/20, Naked Science, CNN, ABC News, CBS News, NBC News, Al Jazeera English, Fox News Channel, The History Channel, Conan, The Science Channel, The Discovery Channel, TLC, Countdown with Keith Olbermann, The Colbert Report, The Art Bell Show and its successor, Coast To Coast AM, BBC World News America, The Opie & Anthony Show, The Covino & Rich Show, Head Rush, The Late Show with David Letterman, and Real Time with Bill Maher.

In 1999, Kaku was one of the scientists profiled in the feature-length film Me and Isaac Newton, directed by Michael Apted. It played theatrically in the United States, was later broadcast on national TV, and won several film awards.^{[citation needed]}

In 2005, Kaku appeared in the short documentary Obsessed & Scientific. The film is about the possibility of time travel and the people who dream about it. It screened at the Montreal World Film Festival and a feature film expansion is in development talks. Kaku also appeared in the ABC documentary UFOs: Seeing Is Believing, in which he suggested that while he believes it is extremely unlikely that extraterrestrials have ever actually visited Earth, we must keep our minds open to the possible existence of civilizations a million years ahead of us in technology, where entirely new avenues of physics open up. He also discussed the future of interstellar exploration and alien life in the Discovery Channel special Alien Planet as one of the multiple speakers who co-hosted the show, and Einstein's Theory of Relativity on The History Channel.

In February 2006, Kaku appeared as presenter in the BBC-TV four-part documentary Time which seeks to explore the mysterious nature of time. Part one of the series concerns personal time, and how we perceive and measure the passing of time. The second in the series deals with cheating time, exploring possibilities of extending the lifespan of organisms. The geological time covered in part three explores the ages of the earth and the sun. Part four covers the topics of cosmological time, the beginning of time and the events that occurred at the instant of the big bang.

On January 28, 2007, Kaku hosted the Discovery Channel series 2057. This three-hour program discussed how medicine, the city, and energy could change over the next 50 years.

In 2008, Kaku hosted the three-hour BBC-TV documentary Visions of the Future, on the future of computers, medicine, and quantum physics, and he appeared in several episodes of the History Channel's Universe series.

On December 1, 2009, he began hosting a 12-episode weekly TV series for the Science Channel at 10 pm, called Sci Fi Science: Physics of the Impossible, based on his best-selling book. Each 30-minute episode discusses the scientific basis behind imaginative schemes, such as time travel, parallel universes, warp drive, star ships, light sabers, force fields, teleportation, invisibility, death stars, and even superpowers and flying saucers. Each episode includes interviews with the world's top scientists working on prototypes of these technologies, interviews with science fiction fans, clips from science fiction movies, and special effects and computer graphics. Although these inventions are impossible today, the series discusses when these technologies might become feasible in the future.^[14]

In 2010, he began to appear in a series on the website Gametrailers.com called Science of Games, discussing the scientific aspects of various popular video games such as Mass Effect 2 and Star Wars: The Force Unleashed.

Kaku is popular in mainstream media because of his knowledge and his accessible approach to presenting complex subjects in science. While his technical writings are confined to theoretical physics, his public speaking and media appearances cover a broad range of topics, from the Kardashev scale to more esoteric subjects such as wormholes and time travel. In January 2007, Kaku visited Oman. While there, he talked at length to select members of that country's decision makers. In an interview with local media, Dr Kaku elaborated on his vision of mankind's future. Kaku considers climate change and terrorism as serious threats in man's evolution from a Type 0 civilization to Type 1.^[15]

He is pictured in Symphony of Science's newest song (as of September 6, 2011), 'The Quantum World.'

On October 11, 2010, Michio Kaku appeared in the BBC program "What Happened Before the Big Bang" (along with Laura Mersini-Houghton, Andrei Linde, Roger Penrose, Lee Smolin, Neil Turok, and other notable cosmologists and physicists), where he propounded his theory of the universe created out of nothing.^[16]

Social policy advocacy[link]

Kaku has publicly stated his concerns over matters including the anthropogenic cause of global warming, nuclear armament, nuclear power and the general misuse of science.^[17] He was critical of the Cassini–Huygens space probe because of the 72 pounds (33 kg) of plutonium contained in the craft for use by its radioisotope thermoelectric generator. Conscious of the possibility of casualties if the probe's fuel were dispersed into the environment during a malfunction and crash as the probe was making a 'sling-shot' maneuver around earth, Kaku publicly criticized NASA's risk assessment.^[18] He has also spoken on the dangers of space junk and called for more and better monitoring. Kaku is generally a vigorous supporter of the exploration of outer space, believing that the ultimate destiny of the human race may lie in extrasolar planets; but he is critical of some of the cost-ineffective missions and methods of NASA.

Kaku credits his anti-nuclear war position to programs he heard on the Pacifica Radio network, during his student years in California. It was during this period that he made the decision to turn away from a career developing the next generation of nuclear weapons in association with Edward Teller and focused on research, teaching, writing and media.^{[citation needed]} Kaku joined with others such as Helen Caldicott, Jonathan Schell, Peace Action and was instrumental in building a global anti-nuclear weapons movement that arose in the 1980s, during the administration of U.S. President Ronald Reagan.

Kaku was a board member of Peace Action and on the board of radio station WBAI-FM in New York City where he originated his long running program, Explorations, that focused on the issues of science, war, peace and the environment.

His remark from an interview in support of SETI, "We could be in the middle of an intergalactic conversation...and we wouldn't even know.", is used in the third Symphony of Science installment "Our Place in the Cosmos".

Personal life[link]

Kaku is married to Shizue Kaku and has two daughters.^[19]

Bibliography[link]

References[link]

External links[link]

Wikimedia Commons has media related to: Michio Kaku

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• Official website
• Michio Kaku on Twitter
• Getting Physical: Dr. Michio Kaku Explains Einstein's Genius
• Russia Takes Aim at Asteroids, op-ed on asteroid defense, Wall St. Journal, Jan. 5, 2010
• The Skeptics' Guide To The Universe interview
• Michio Kaku at the Internet Movie Database
• Michio Kaku on National Public Radio
• About Michio Kaku
• Video: Michio Kaku discusses Physics of the Future on March 23, 2011, on Forum Network.
• In Depth interview with Kaku, October 3, 2010

Antony Garrett Lisi
Antony Garrett Lisi in Iceland, for the 2007 FQXI conference
Born	January 24, 1968
Nationality	American
Fields	Theoretical physics
Institutions	none: independent
Alma mater	UCLA UCSD
Known for	"An Exceptionally Simple Theory of Everything" Surfing

Antony Garrett Lisi (born January 24, 1968), known as Garrett Lisi,^[1] is an American theoretical physicist and adventure sports enthusiast. Lisi works as an independent researcher without an academic position. He is a strong proponent of balance in life, in his case between scientific research and enjoyment of the outdoors.^[2][3][4]

Lisi is known for "An Exceptionally Simple Theory of Everything," a paper proposing a unified field theory based on the E₈ Lie group, combining particle physics with Einstein's theory of gravitation. The theory is incomplete and not widely accepted by the physics community.

Biography[link]

Early life[link]

Born in Los Angeles and raised in San Diego, California,^[5] Lisi graduated the Cate School (south of Santa Barbara, California) in 1986. He learned to surf in San Diego, where he traveled between surf breaks in an old VW Bus.^[6] Lisi went on to receive two B.S. degrees with highest honors in physics and mathematics from the University of California, Los Angeles in 1991. Lisi received a Ph.D. in physics from the University of California, San Diego in 1999.^[7]

After the Ph.D.[link]

After getting his Ph.D., Lisi left academia and moved to Maui — expressing his dissatisfaction with the state of theoretical physics:

I got my PhD and looked at my options. I love differential geometry, general relativity, and particle physics. But the only options available then for a postdoc in those combined areas were in string theory, and I thought string theory was overly speculative. There are many really impressive aspects of strings — anomaly cancelation in particular — but there are other things that just seem wild and physically unsubstantiated. I had gotten lucky by investing my graduate stipend in a little company many thought was going out of business (AAPL), so I decided to go to Maui, learn to windsurf, and work on physics on my own.^[8]

On Maui, Lisi volunteered as a staff member at a local Sudbury school, and split his time between working on his own physics research and surfing.^[9]

While living in a customized van with his girlfriend, Crystal Baranyk, Lisi taught physics classes at University of Hawaii – Maui College.^[9] After two years on Maui, Lisi says he was offered a tenure track teaching position at the local college, but turned it down (even though he was nearly broke) because it wouldn't have given him enough time for his physics research.^[1] At the same time, he submitted a grant application to the newly formed Foundational Questions Institute (FQXi). Lisi says the decision to turn down the job offer and hope for FQXi funding was "a hell of a gamble."^[1][10]

Academic reentry[link]

On July 31, 2006, Lisi was awarded an FQXi grant to develop his research in quantum mechanics and unification.^[11] The grant allowed Lisi to devote his full attention to physics and create his personal research wiki, Deferential Geometry.^[12] On June 9, 2007, Lisi realized that the algebraic structure he had constructed to unify the standard model of particle physics with general relativity partially matched part of the algebraic structure of the E₈ Lie group.^[13][14]

On July 21, 2007, Lisi traveled to the inaugural FQXi conference in Reykjavik, Iceland. He was invited to give several academic talks.^[9] On invitation from Lee Smolin, Lisi visited the Perimeter Institute for Theoretical Physics in October, and posted his paper, "An Exceptionally Simple Theory of Everything,"^[15] to the arXiv on November 6, 2007. Discussions of Lisi's theory developed rapidly over most major physics blogs,^[6] and the story of Lisi's theory and personal history was reported by many online and traditional media sources around the world.^[16][17][18]

Lisi presented at the TED Conference on February 28, 2008,^[19] and has since presented several academic talks and colloquia.^[20]

On July 8, 2009, at a FQXi conference in the Azores, Lisi made a public bet with Frank Wilczek that superparticles would not be detected by July 8, 2015.^[21]

In July, 2010, mathematicians and physicists met with Lisi at the Banff International Research Station in Alberta, Canada, for a week to discuss his theory.^[22]

Physics research[link]

Work on quantum mechanics[link]

On May 8, 2006, in an arXiv preprint, "Quantum mechanics from a universal action reservoir,"^[23] Lisi proposes that the path integral formulation of quantum mechanics can be derived from information theory and the existence of a universal action reservoir.^[24]

Deferential Geometry[link]

Lisi is an early practitioner of open notebook science.^[25] Lisi created his "personal wiki notebook in theoretical physics" — the Deferential Geometry website — by using TiddlyWiki and jsMath.^[12] Lisi uses this wiki to organize his research notes in theoretical physics, referring to this as "open source physics."^[11][26]

An Exceptionally Simple Theory of Everything[link]

Lisi's main work in theoretical physics is his Exceptionally Simple Theory of Everything, which proposes a unified field theory combining a grand unification theory of particle physics with Albert Einstein's general relativistic description of gravitation, using the largest simple exceptional Lie algebra, E₈. In a paper posted to the physics arXiv on November 6, 2007,^[15] and in a popular article published in Scientific American in December, 2010,^[27] Lisi describes his proposal that gravity, the standard model bosons and fermions can be unified as parts of an E₈ superconnection. This unified field theory attempts to describe all fundamental interactions observed in nature, as a possible theory of everything, unifying Albert Einstein's general relativity with the standard model of particle physics. The theory, called E8 Theory, also predicts the existence of many new particles.^[28]

Lisi designed a web application, the Elementary Particle Explorer,^[29] for visualizing the charge structure of the elementary particles in the standard model, in grand unified theories, and in E8 Theory.

Lisi's theory has been applauded but also criticized in the scientific community.^{[30][31][32][33]} He has addressed the criticism, while acknowledging that the theory is incomplete. In a Scientific American post, Garrett himself states:

(the 3 generation) ... issue remains the most significant problem, and until it is solved the theory is not complete and cannot be considered much more than a speculative proposal. Without fully describing how the three generations of fermions work, the theory and all predictions from it remain tenuous.^[34]

Adventure sports[link]

Garrett Lisi is an adventure sports enthusiast — surfing, snowboarding, and kitesurfing at the expert level as well as participating in many other adventure sports.^[2][6][35] In an interview for Wired News, Lisi says:

Surfing and snowboarding are what I do for fun – to get out and play in nature. We live in a beautiful universe, and I wish to enjoy it and understand it as best I can. And I try to live a balanced life. Surfing is simply the most fun I know how to have on this planet. And physics, and science in general, is the best way of understanding how everything works. So this is what I spend my time doing. I do what I love, and follow my interests. Shouldn't everyone?^[36]

Lisi brings some of his physics to his sports activities.^[37] During graduate school and years in Maui, most of Lisi's surfboards were adorned with the wave equation as decorative art.^[2][38] And when riding an extra-long carving board, for alpine snowboarding, in Colorado and Tahoe, Lisi always wears a long white lab coat.^{[2][6][39][40]} He has also become a sponsored team rider for an Oregon surfboard manufacturer, 42 Surfboards.^[36]

Although concentrating on surfing, kitesurfing and snowboarding, Lisi participates in a wide variety of adventure sports.^[41] On his online journal, Lisi describes his experiences surfing, snowboarding, windsurfing, sailing, kitesurfing, mountain biking, skateboarding, motorcycling, cliff diving, rock climbing, hang gliding, paragliding, backpacking, water skiing, wakeboarding, flying, sky diving, and scuba diving.^[9] Lisi is working on a film about young scientists who combine cutting-edge research with adventure sports.^[42]

Science hostel[link]

Lisi proposes the creation of a more casual kind of science institute — a science hostel  — which he says "would essentially be large houses in beautiful locations where theorists could live and work."^[39] Citing his experience living in Maui and the mountains of Tahoe and Colorado, Lisi says that for theoretical research it is good to have opportunities for hiking and things to do outside in attractive environments.^[43][44] Describing the idea more formally, Lisi says:

The physical requirements for conducting scholarly research have changed dramatically with the rise of the internet. It is now viable for researchers with laptop computers to work autonomously – with access to current articles and communication channels on par with the resources available at large universities. These new circumstances motivate the creation of a new kind of research enterprise: a Science Hostel. By providing places to live and work with other researchers, in beautiful locations, a Science Hostel could increase creative productivity and overall quality of life for scholars in the internet age.^[45]

Any theory of everything should indeed be beautiful.^[46]

Invention USA[link]

In December 2011, Lisi began starring, with Reichart Von Wolfsheild, in Invention USA, a History channel documentary television series.^[47]

References[link]

External links[link]

• Antony Garrett Lisi's home page
• @garrettlisi on Twitter
• TED Talks: Garrett Lisi on "The Beauty of Particle Physics" at TED in 2008
• Deferential Geometry – Lisi's personal research wiki
• Elementary Particle Explorer – a Flash application designed by Lisi
• Lisi's publications in high energy physics
• Scientific American: A Geometric Theory of Everything – an article co-authored by Lisi in 2010.
• Jornal Ciência: Físico do Havaí quer explicar o Universo com figura geométrica - an article on Lisi in a Brazilian science portal, 03/05/12.