1. TRADITIONAL SUBJECT-MATTER OF CONDENSED MATTER THEORY: CRYSTALLINE SOLIDS, LIQUIDS ….
On the cosmic scale:
Stars
density 
Interstellar Space
 temperature
Liquids and crystalline solids: ~ 1 part in 1011!
And yet…
10– – – – –
Temp. of Outer Space
Room Temp.
9/5/ :54 AM

2. WHAT IS (MODERN) CONDENSED MATTER THEORY?
by a liberal definition, the study of any system where we
— must deal with a very large number of mutually interacting objects
— have incomplete description at the level of single objects
— must allow for the effects of a noisy “environment”
— can (usually) get little useful information out of an exact “microscopic” description, even were one available
— can compare theoretical predictions directly with experiment
Some non-traditional areas of applicability of condensed matter theory:
polymers
nano/mesoscopic systems
glasses (amorphous materials)
high-temperature (cuprate) superconductors
neural networks
the human genome
the stock market
the Internet…

3.  ? Some generic principles we have learned:
— Effects of interactions between ~1023 “objects” (atoms, etc.) may be qualitatively different from those of 2–, 3– … n-body interactions
— essential to develop phenomenological, intermediate-level models
— models do not need to be derivable from “microscopic” description, but must be consistent with it.
 ?
— quite different types of structure at the “microscopic” level may nevertheless lead to “universal” behavior at the macro-level
exx: 2nd order phase transitions
? Glasses
?? 1/f noise
— sometimes useful to change the question (ex: Landau theory of Fermi liquid)

4. A TYPICAL “INTERMEDIATE-LEVEL” MODEL: THE CONCEPT OF A QUASIPARTICLE
object which may be a very complex combination of “elementary” particles, but nevertheless behaves very much like a “particle” itself.
examples:
fermionic quasiparticle in Landau Fermi liquid
phonon in crystalline solid
phonon in superfluid liquid 4He
Laughlin quasiparticle in fractional quantum Hall effect (“fractional” charge, statistics)
“nonabelian” anyons intrinsically many-body phenomenon!
screening cloud
compression rarefaction
extra charge
,  ,

6. Liquid 4He in Annular Geometry
A Spectacular Example of how “Many-Body” Effects can Produce Qualitatively New Forms of Behavior:
Liquid 4He in Annular Geometry R
Rotate container at T>T with <½c: liquid rotates with container. Cool below T: liquid comes out of equilibrium with container, to rest in () frame of laboratory. (“Hess-Fairbank” effect/nonclassical rotational inertia)
Set liquid into “fast” rotation (»c), then stop container: liquid continues to rotate indefinitely (“persistent currents”)
“quantum unit of rotation”
Both effects consequences of
quantum mechanics: for any individual atom,
Bose-Einstein condensation (“BEC”) : (at T=0), all atoms must behave identically
(for (6)): (repulsive) inter-atomic interactions
BEC amplifies microscopic effects to macroscopic level!

7. WHY AN ICMT NOW?
— unprecedented awareness, in many areas of science, of crucial significance of collective behavior.
— the bread and butter of condensed matter theory!
Material Science
Traditional Solid-State Physics
Theoretical Chemistry
Astrophysics
Neuroscience
Modern Condensed-Matter Theory
Medical Physics
Geophysics
Biology
High-Energy Physics
Nanoscience
Cosmology
Quantum Information
Quantum information: originally, dealt with well isolated atomic-level systems
In 2008: (a) solid-state qubits, even based on collective degrees of freedom (e.g., SQUIDs)
(b) topological ideas in quantum computing

8. CONDENSED MATTER THEORY: WHAT LIES IN THE FUTURE?
— partnerships beyond traditional boundaries
— exploration along “axis” of complexity
— more concentration on individual quantum states
— technological spinoffs, e.g. ?? RT superconductivity??
— input to fundamental questions of physics:
(a) quantum measurement paradox: B C
“neither B nor C” “neither dead nor alive”?
(b) arrow of time: A K Q J
. . . 2 K 8 J A 7
intersection of considerations from thermodynamics, EM theory, cosmology(?), biology, psychology…. and condensed matter theory!