Lecture 1

Statistical PhysicsPart of B20SN2

Dr. Sabrina ManiscalcoReader in Physics

Research fields:

Quantum PhysicsQuantum Information Processing & Quantum ComputersQuantum TechnologiesOpen Quantum Systems

Office: DB G.04Tel: 0131 451 3053email: S.Maniscalco@hw.ac.uk

Book

Statistical and Thermal PhysicsHarvey Gould & Jan Tobochnik

http://stp.clarku.edu/notes/

Questions: Mondays 3 pm - 4 pmDB G.04(Send an email before)

What is expected from you

0) Attend all the classes 1) Study (hard) from the book2) Use the slides as guidelines to remember the contents of the lectures and NOT as study material3) Ask questions and interrupt me if you don’t understand something4) Do all the problems of the tutorials 5) Give feedback on the lectures6) Exam: Three Problems on the Statistical Physics part. Math is not simple.

THIS IS NOT AN EASY COURSE!

Microscopic and Macroscopic

Macroscopic

Macroscopic

Superconductors

Neutron star

Stock Market

STAT

IST

ICA

L M

ECH

AN

ICS

MACROSCOPIC - THERMODYNAMICS

Different types of questions

1. How does the pressure of a gas depend on the temperature and the volume of its container?2. How does a refrigerator work? How can we make it more efficient?3. How much energy do we need to add to a kettle of water to change it to steam?4. Why are the properties of water different from those of steam, even though water and steamconsist of the same type of molecules?5. How and why does a liquid freeze into a particular crystalline structure?6. Why does helium have a superfluid phase at very low temperatures? Why do some materials exhibit zero resistance to electrical current at sufficiently low temperatures?7. In general, how do the properties of a system emerge from its constituents?8. How fast does the current in a river have to be before its flow changes from laminar to turbulent?9. What will the weather be tomorrow?NON-EQUILIBRIUM PHENOMENA

The goal of statistical mechanics

The goal of statistical physics is to begin with the microscopic laws of physics that govern the behavior of the constituents of the system and deduce the properties of the system as a whole

The goal of statistical mechanics

Microscopic

Macroscopic

A glass of HOT waterin a COLD ROOM

The arrow of time!

What other phenomena exhibit a direction of time?

Humpty Dumpty sat on a wallHumpty Dumpty had a great fallAll the king’s horses and all the king’s menCouldn’t put Humpty Dumpty back together again.

Is there a direction of time for a single particle?

F =dp

dt

Newton’s second law is time reversal invariant

There is no direction of time at the microscopic level

The behaviors of macroscopic bodies and single particles are very different

Why the reverse process does not occur?

Conservation of Energy?

NO!

Energy is transferred from one degree of freedom to many degrees of freedom while the total energy is conserved

Increase in entropy

Conversion of stored energy into heating

No limit to the efficiency of conversion

Conversion of stored energy into work

Conversion of stored energy into useful work

Can we convert stored energy into useful work with 100% efficiency?

NO, we must necessarily “waste” some of the energy

It is plausible that it is inefficient to transfer energy from many degrees of freedom to only a few. In contrast, the transfer of energy from a few degrees of freedom (the firewood) to many degrees of freedom (the air in your room) is relatively easy

The second law of thermodynamics (historically conceived before the first law)

The importance of entropy

The direction of time

The inefficiency of converting stored energy into work

An increase of entropy is associated to a decrease in the ability to do work

Richard Feynman (Nobel Prize in Physics, 1965) talks about “jiggling atoms”

http://www.bbc.co.uk/archive/feynman/10700.shtml

Statistical and Thermal PhysicsHarvey Gould & Jan Tobochnik

http://stp.clarku.edu/notes/

Lecture 1: Chapter 1 pages 1-5