Strings:  Vibrating strands of “energy,” at the heart of matter, photons and gravity.  The different frequencies of strings produce the different subatomic particles.  A fundamental string is called an f-string.  String theory is not yet testable or observable.

Branes:  “Membranes” or other places where strings attach.  For example,

D0 Brane:  A point particle.  An f-string can end there.

D1 Brane:  Like a string, but with more mass per unit length.  Also called a D-string.  An f-string can end there.

D2 Brane:  A brane with two dimensions.

D3 Brane:  A brane with three dimensions.  An f-string or D-string can end there.

Open Strings:  Have one or both ends tied to a brane.

Closed Strings:  Ends are attached to each other. 

Gravitons:   Hypothetical elementary particles/closed strings with zero mass.

M-Theory:  String theory with eleven-dimensional supergravity.  (Alternate theories stipulate 10 or 26 dimensions.)  M-Theory allows a string to stretch into a brane.  Eliminates tachyons. 

Relativistic String:  The string of String Theory.

String Worldsheet:  A “topographical map” of how a string is supposed to move in spacetime.

Supergravity:   A theory that combines the principles of supersymmetry and general relativity.

Supersymmetry:   A fermion must exist for every boson and a boson for every fermion. 

Tachyon:   A relativistic string with a negative mass squared (an imaginary number).

Particle Physics I-A

Quarks:   Elementary particles in the Standard Model of Particle Physics, and fundamental constituents of matter.  Quarks have quirks: electric charge, color charge (which has nothing to do with color), mass, spin and flavor (which has nothing to do with taste).

Hadron:  A composite particle made of quarks held together by the strong nuclear force.  Hadrons are baryons (made of 3 quarks) or mesons (made of a quark, antiquark and gluon field).  All free hadrons except the proton and anti-proton are unstable.

Boson: A particle with an integer spin.  Bosons can be fundamental particles such as photons, the Higgs Boson, gluons and the hypothetical (massless) graviton.  Bosons can be composite particles such as the meson.  Bosons are often force carrier particles.  More than one boson can occupy the same quantum state at any given time. 

Fermion:  A particle with a half-integer spin.  Fermions can be elementary particles such as an electron.  Fermions can be composite particles such as protons, neutrons or the helium-3 atom.  Fermions are usually associated with matter.  A particle containing an odd number of fermions is itself a fermion: it will have half-integer spin.  Only one fermion can occupy a particular quantum state at any given time.  If more than one fermion occupies the same physical space, at least one property of each fermion, such as its spin, must be different.

Force Carriers:

            Photons:  The force carriers of the electromagnetic field.

            W & Z bosons:  The force carriers which mediate the weak nuclear force.

            Gluons:  The fundamental force carriers underlying the strong nuclear force.

            Higgs bosons:  Force carriers that give other particles mass.

Duality:  Remember the old Sesame Street song: “One of these things is not like the other?”  With a duality, “One of these things is not like the other but can be.”

General Relativity:  Describes the curvature of spacetime and distribution of matter throughout spacetime.  Matter warps space.  Warps and curves in the fabric of space create gravity.

Special Relativity:  (E = MC²)  A special case of general relativity that does not include gravity.

Heisenberg Uncertainty Principle:  The more precisely the position of some particle is determined, the less precisely its momentum can be known, and vice versa.

Singularities:  Spacetime boundaries, such as paths of light and falling particles coming to an abrupt end.

Standard Model of Particle Physics:  Incorporates electromagnetic, weak and strong nuclear interactions, but not gravity.

Thank you to all who attended the “String Theory for Dummies” panel on 9/3/12.  In addition, thank you Marion Holland for creating “A Big Ball of String,” published in 1958.  I have read the book to children and grandchildren and recently found and purchased a copy at a “book rescue” site online.  May your beautiful story last forever.

Warm wishes,

Laurel Anne Hill
Author of “Heroes Arise”  (http://www.laurelannehill.com)