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DYK-12 :: What is a gauge? as Explained by Pankaj Sharan

Node id: 3103page


The following (from notes for a lecture I was preparing) might help explain the context: The first gauge theory was Hermann Weyl's extension of Einstein's general theory of relativity with a parallel transport that can change the scale or 'gauge' of lengths of the transported vector. About this one can read in P. G. Bergman's book on Relativity. The Hamiltonian formulation of electrodynamics, and in particular, the replacement of \(\vec{p}\) by \(\vec{p}-e\vec{A}/c \) was given by Larmor in his book "Aether and Matter", Cambridge (1900). [quoted by Pauli in ''General Principles of Quantum Mechanics" , Section 4. (Tr. by P. Achuthan and K. Venkatesan of 1958 German edition) Allied, New Delhi 1980.] In quantum mechanics the 'canonical momentum' \(\vec{p}-e\vec{A}/c\) becomes \(-i\hbar[\nabla-ie\vec{A}/(\hbar c)]\). The gauge invariance of the Schrodinger theory under \(\vec{A}\to \vec{A}+\nabla f\) and \(\phi\to \phi-(e/c)\frac{\partial f}{\partial t} \) when \(\Psi\) is changed by a phase was first given by V. Fock (1927). The analogy of this group of transformations to the Weyl theory on gravitation and electricity was pointed out by F. London (1927). The connection of this group to charge conservation was pointed out by Weyl while writing variational principle for the wave equation. [See Pauli as above.]

kapoor's picture 20-02-08 16:02:30 n

DYK-10 Schrodinger was never comfortable with quantum jumps

Node id: 2962page
kapoor's picture 20-02-08 16:02:30 n

EM-Theory :: Facts to be Remembered

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kapoor's picture 20-02-08 16:02:30 n

Quantum Mechanics :: Facts to be Remembered

Node id: 2236page

  Content Under Development

kapoor's picture 20-02-08 16:02:30 n

PTR/EM-04001 Properties of Conductors

Node id: 2235page
kapoor's picture 20-02-08 16:02:30 n

DYK-08 Who proposed electron spin first and what happened to the proposal?

Node id: 2114page
kapoor's picture 20-02-08 16:02:30 n

PTR/QM-06003 --- Probabilty and average value

Node id: 1970page
kapoor's picture 20-02-08 16:02:30 n

PTR/QM-06002 --- Dynamical Variables as hemitian operators

Node id: 1969page
kapoor's picture 20-02-08 16:02:30 n

PTR/QM-06001 --- States of a quantum system

Node id: 1968page
kapoor's picture 20-02-08 16:02:30 n

DYK-07 How good is Newtonian mechanics for planetary motion?

Node id: 1899page
kapoor's picture 20-02-08 16:02:30 n

DYK-06 Position Operator in Relativistic Quantum Mechanics

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kapoor's picture 20-02-08 16:02:30 n

DYK-05 Change in Sign of Fermion Wave Function under 2$\pi$ Rotation

Node id: 1830page

It is well known the wave function of a fermion changes sign under rotation by \(2\pi\). Has this been verified experimentally?

kapoor's picture 20-02-08 16:02:30 n

DYK-04 Who Revived the Klein Gordon Equation?

Node id: 1828page

The Klein Gordon equation in its original  interpretation suffered from problem of negative probabilities. After quantum electrodynamics was successfully formulated, the second quantized Klein Gordon equation was shown to give a consistent formulation for spin zero particles. WHO DID THIS WORK?

kapoor's picture 20-02-08 16:02:30 n

DYK-03 Jacobi Action Principle

Node id: 1827page

Jacobi Action Principle
A Second Variational Principle for Conservative Systems

Hamilton.'s action principle in classical mechanics is widely taught. There is a lesser known, but important Jacobi principle which is like Fermat's principle for waves. This form of action principle  was used by Schrodinger to arrive at his hafous equation for qunatum mechanics of a point particles. 

 

 

kapoor's picture 20-02-08 16:02:30 n

DYK-02 Connection beteen Keplers and Hooke's force laws

Node id: 1826page

Coulomb's force law and Hooke's law are connected by a transformation called Bohlin's transformation.

$\newcommand{\DD}[2][]{\frac{d^2#1}{d#2^2}}$

kapoor's picture 20-02-08 16:02:30 n

Random Mix-06 An example of Quantum Effects in Stars

Node id: 851page

An example of Quantum Effects in Stars

Sarita Vig
Department of Earth and Space Sciences
Indian Institute of Space Science and Technology (IIST)
Valiamala, Tiruvananthpuram 695547, INDIA

kapoor's picture 20-02-08 16:02:30 n

Works of Masters always have something to offer

Node id: 723page

I take the best from every one. But GOLD FROM OLD,
There is always something to learn from  MASTERS;

In this age of internet, there is a tendency to open internet and learn from Wikipedia and similar sites. While this has its own advantages for  a mature learner, I recommend that a beginner must learn from the masters even though the learning curve may look very steep.

This collection is an attempt to encourage younger generation to leart role of contibuting  to the subject and from the very best.

There are many who contributed to pedgogy and teaching. Many old texts become 'obsolete' simply because is it fashionable to go for the latest.  It would be foolhardy to ignore these and other works, so we include here snippets and quotes etc. from many other sources too.

It is  hoped this will provide incentive to the younger generations to ask for more.

"Choose the very best from every one" 

 

 

kapoor's picture 20-02-08 16:02:30 n

Sample Grading by Category

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kapoor's picture 20-02-08 16:02:30 n

Sample Rapid Fire Quiz

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kapoor's picture 20-02-08 16:02:30

Sample Quiz : Identities in QM

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kapoor's picture 20-02-08 16:02:30

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