The Superstring Adventure Robert Myers (PITP; February 11, 2008)
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Transcript of The Superstring Adventure Robert Myers (PITP; February 11, 2008)
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The Superstring Adventure
Robert Myers(PITP; February 11, 2008)
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New Yorker magazine:
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Physics of the 20th century: A grand synthesis andprogression of ideas!
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Physics of the 20th century: A grand synthesis andprogression of ideas!
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Einstein:Gravity: It’s all just straight lines!
Special Relativity (1905):Space and time are inextricably linked Spacetime
General Relativity (1915):Gravity is a manifestation of spacetime curvature.
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General Relativity: a rich source of new ideas
Black holes
Gravitational waves
Expanding universe
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General Relativity is rigorously tested!!
• Deflection of Light by the Sun• Gravitational Redshift• Precession of the Perihelion of Mercury• Time Delay of Light, . . . . .
Hulse and Taylor:Nobel Prize in 1993!!
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Global Positioning System (GPS):
Accurate positioning requires accounting for affectsof general relativity on clocks in orbit and on earth
General Relativity is rigorously tested!!
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General Relativity is rigorously tested!!
• Deflection of Light by the Sun• Gravitational Redshift• Precession of the Perihelion of Mercury• Time Delay of Light, . . . . .
Hulse and Taylor:Nobel Prize in 1993!!
General Relativity is the geometric arena of physics on very large scales: planets, stars, galaxies, cosmology
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m000004000000.
Quantum Mechanics (or Quantum Field Theory) is the probabilistic arena of physics on very
small scales
Quantum fluctuations are manifest in
behavior of subatomic particles
Positions are uncertain
for the very small !
electronbeam
3 m103 10electron Å
m104 30drop rain
waterjet
30 digits
)cm1m01.m10( 2
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Elementary Particles ( 10 m )─17
m10 10 m10 14 m10 15
Standard Model of Subatomic Physics:above particles plus interactions
(and ~20 free parameters)W
e
e
Quantum Field Theory is the probabilistic arena of physics on very small scales
Fermions: electron, muon, tauon neutrinos (3 flavors) quarks - up, down, strange, charm, bottom, top
Bosons (Force Mediators): photon (electromagnetism) gluon (strong) , Z (weak)W
Higgs particle
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Quantum theory is rigorously tested!!
electrons are tiny magnets
0307304319002.2calculated
8373304319002.2measured
precise value of magnetic moment depends on quantum fluctuations
(neither answer absolutely correct)
Example:
10
measured
measuredcalculated 10
2 with 4 gmeg ee
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• band structure in materials semiconductor technology• Bose-Einstein condensation superfluids, superconductors• quantum Hall effect, neutron diffraction,• electron microscopy, lasers,• magnetic resonance imaging,• · · · · · · ·
Quantum Theory: a rich source of new ideas
Nobel prizes galore!!
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Subatomic Physics
Elementary Particles ( 10 m )─17
a theory of strings!
Strings tame the particle zoo!m10 35
Fermions: electron, muon, tauon neutrinos (3 flavors) quarks - up, down, strange, charm, bottom, top
Bosons (Force Mediators): photon (electromagnetism) gluon (strong) , Z (weak)W
Higgs particle
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Superstrings: the theory of subatomic physics
The essential idea: with sufficient resolution, all elementary particles are one-dimensional objects (strings)
all particle types are the same kind of stringvibrating or rotating in different ways
electron
photon
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Superstrings: the theory of subatomic physics
The idea: with sufficient resolution, all elementary particles are one-dimensional objects (strings)
all particle types are the same kind of stringvibrating or rotating in different ways
the typical size of the strings is the fundamentalscale of the theory, m10 35S
Interactions?
S
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coupling constant, g,determines probability
of interaction
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Superstrings: the theory of subatomic physics
with resolution, , all elementary particles are one-dimensional objects (strings)
m10 35S
interactions are geometric joining and splittinggoverned by coupling constant, g
with these simple rules get appropriate particlespecies and interactions to match Standard Model
S
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Subatomic Physics
Elementary Particles ( 10 m )--17
Fermions: electron, muon, tauon neutrinos (3 flavors) quarks - up, down, strange, charm, bottom, top
Bosons (Force Mediators): photon (electromagnetism) gluon (strong) , Z (weak)W
Higgs particle
a theory of strings!
What’s missing here?Graviton (gravity!!)
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Superstrings: the theory of gravitational physics
m10 353
c
GS
consistency requires appearance of the graviton!
at long distances much greater than , reproducesEinstein’s gravitational equations
TGgR 8R 21
sets the string length scale:
Superstrings naturally provides a unified frameworkfor Quantum Field Theory and General Relativity
S
Newton’s constant
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SUPERSTRINGTHEORY
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Superstring theory: The devil is in the “details”
• Predicts we live in 10 spacetime dimensions!! Experimental update: we live in 4 dimensions!
Big fix: Perhaps we haven’t seen the extra dimensions yet.
(1 time and 3 space)
Benefit: richness of four-dimensional physics comes from geometry of the extra dimensions
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Superstring theory: The devil is in the “details”
• Predicts we live in 10 spacetime dimensions!! Experimental update: we live in 4 dimensions!
• Predicts extra particles we haven’t seen yet!
(Supersymmetry: each fermion is accompanied bya bosonic partner of the same mass)
Big fix: Perhaps we should look harder.
Benefit: SUSY tames the short distance(quantum) fluctuations of the theory
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Superstring theory: Details, details, details, ….
• Have five consistent superstring theories: Type I, Type IIA, Type IIB,
Heterotic E8 X E8, Heterotic SO(32)
• Conjecture: all known string theories are different solutions of single fundamental theory
M-theory
one universe four too many theories?!?
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String theory is more than a theory of strings!
• D-branes: string theory contains other kinds of objects extended in 0, 1, 2, . . . dimensions
particles
strings membranes
p-branes
2
21 p
s
pT
gextremely heavy in weak coupling
extremely important in strong coupling
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Superstring theory: Unique theory of everything
• M-theory Conjecture: all known string theories are different solutions of single fundamental theory
M-theory also includes 11-dimensional supergravity!
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M-THEORY
But contact with experiment is crucial
??Physics at Planck scale??
String/M-theory is a rich source of new ideas
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Superstring theory: a theory looking for a good experiment
accelerator experiments: probe 1012 eV and beyond Tevatron, Large Hadron Collider, ….
cosmological experiments: extreme conditions of early universe may have left stringy imprints
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Cosmology: extreme conditions of early universe give a window on small scales and high energies
Present
Past
Future
String physics is manifest
Stringy relics orimprints now?
We need to understand theoptics of our “microscope”
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Superstring theory: a theory looking for a good experiment
accelerator experiments: probe 1012 eV and beyond Tevatron, Large Hadron Collider, ….
cosmological experiments: extreme conditions of early universe may have left stringy imprints
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Superstrings:a mathematical model of our physical universe
Studies of string theory draw upon an enormous range of modern mathematics:
complex analysis, group theory, fibre bundles, gerbes,topology, differential geometry, mirror symmetry,
K-theory, derived categories, noncommutative geometry
We are still groping for the language of string theory!
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Superstrings:a mathematical model of our physical universe
We are still searching for the full picture!
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early 1900’s ─Ernst Mach: “atoms are physically unverifiable entities”
early 1990’s ─ individual atoms are manipulated using atomic force microscopy
For superstrings, the adventure is still only beginning!