math and physics play

notes for phy450, relativistic electrodynamics, now available on paper from amazon.

March 4, 2019 math and physics play No comments , , ,

My notes from the spring 2011 session of  Relativistic Electrodynamics (PHY450H1S) are now updated to use a 6×9″ format (387 pages), and are available on paper from amazon.  This was the second course I took as a non-degree physics student, and was taught by Prof. Erich Poppitz.

These notes pages, 6×9″) are available in a few formats:

  • In paper (black and white) through amazon’s kindle-direct-publishing for $11 USD.
  • In color, for free as a PDF.
  • from github as latex, scripts, and makefiles.

Links or instructions for the formats above are available here.

Changelog.

phy450.V0.1.9.pdf

  • switch to 6×9″ format
  • fix a whole bunch of too-wide equations, section-headings, … that kdp finds objectionable.
  • suppress page numbers for 1st page of preface, contents, index and bib. This is a hack for my hack of classicthesis, because I don’t have the 6×9 layout right, and the page numbers for that first page end up in an unprintable region that kdp doesn’t allow.
  • add periods to chapter, figure, section, problem captions.
  • remove lots of blank lines before and after equations (which latex turns into paragraphs). That cuts 10s of pages from the book length!
  • move version numbers into separate file (make.revision)

my phy452 stat mech notes available in paper on amazon

March 2, 2019 math and physics play No comments

My notes (6×9″ ~400 pages) for the winter 2013 session of the University of Toronto Basic Statistical Mechanics course (PHY452H1S), taught by Prof. Arun Paramekanti, which I took as a non-degree student, are now available for purchase on paper.  Available formats include:

  • Printed (6×9″ black-and-white) from kindle-direct-publishing, for $10.99 USD,
  • as a free PDF,
  • or by cloning the github repositories that host the latex sources.

Links to the various copies are available here.  I suspect that nobody will buy this (although there are lots of solved problems that might be of interest), but I wanted a printed reference copy for myself, and this was an extremely cheap way to get a bound copy (i.e. $6 USD plus shipping for a “not for resale” review draft).

Changelog (since last posted version)

phy452.V0.1.10.pdf

  • Re-export mathematica based figures as .pdf instead of .png
  • Add commas and periods into equation,dmath contexts.
  • remove blank lines between text and equation/dmath that are connected.
  • switch to 6×9 format for kindle direct publishing and reformat various equations that overflowed page boundaries.
  • use tcolorbox for tables
  • suppress page numbers for list of figures, table of contents, and first page in chapters.This is a hack to deal with my hacking of classicthesis.sty, as it wants to put some of those page numbers in an unprintable region that kdp doesn’t like (and won’t ignore.)
  • replace crude battery/resistor diagram with an svg based figure (with transparency)
  • shrink various figures.
  • periods on chapter, section, and figure captions.
  • move versioning to separate file: make.revision

Antenna theory notes

February 18, 2019 math and physics play No comments

I’ve made a small update to my old PDF notes for the antenna theory class that I took in 2015.

The changes since the last posted version are:

  1. The 2D Mathematica based figures are now updated to use PlotStyle -> Thick, which I think looks better when embedded.  Since I used Mathematica, Julia, Matlab and hand-drawn figures, there’s not much consistency in the figure styles.
  2. The hyperlinks to the web pages I’d created to run the various CDF Manipulate notebooks have also been removed, since Wolfram dropped the ball and never implemented support for 64-bit browsers.

Unfortunately, the 3D figures from various Mathematica 3D plots are really slow to render (at least in Adobe Acrobat), which is also annoying.  I’m not sure what the best way to deal with that would be.

Condensed matter physics notes

February 16, 2019 math and physics play No comments , , ,

Here’s an update of my old Condensed Matter Physics notes.

Condensed Matter

Along with a link to the notes, are instructions on building the PDF from the latex and the github clone commands required to make a copy of those sources.  Mathematica notebooks are also available for some of the calculations and plots.

classical optics notes.

February 15, 2019 math and physics play No comments , , ,

Here’s an update of my old classical optics notes.  Along with a link to the notes, are instructions on building the PDF from the latex and the github clone commands required to make a copy of those sources.  Mathematica notebooks are also available for some of the calculations and plots.

Looks like most of the figures were hand drawn, but that was the only practical option, as this class was very visual.

Continuum mechanics (fluid dynamics) notes posted.

February 13, 2019 math and physics play No comments

I’ve posted a refreshed version of my old fluid mechanics course notes (aka Continuum mechanics).  Also included are instructions to clone the git repositories, and make the pdf from the latex sources (which would allow customization if desired).

Updated statistical mechanics notes.

February 13, 2019 math and physics play No comments

I’ve posted a minor update to my old stat mech notes, plus instructions on how to clone the github repos and the latex, should somebody wish to attempt to fork these notes for their own purposes.  Enjoy!

Mathematica notebooks updated, and a bivector addition visualization.

February 10, 2019 math and physics play No comments , , ,

This blog now has a copy of all my Mathematica notebooks (as of Feb 10, 2019), complete with a chronological index.  I hadn’t updated that index since 2014, and it was quite stale.

I’ve also added an additional level of per-directory indexing.  For example, you can now look at just the notebooks for my book, Geometric Algebra for Electrical Engineers.  That was possible before, but you would have had to clone the entire git repository to be able to do so easily.

This update includes a new notebook written today, which has a Manipulate visualization of 3D bivector addition that is kind of fun.

Bivector addition, at least in 3D, can be done graphically almost like vector addition.  Instead of trying to add the planes (which can be done, as in the neat illustration in Geometric Algebra for Computer Science), you can do the task more simply by connecting the normals head to tail, where each of the normals are scaled by the area of the bivector (i.e. it’s absolute magnitude).  The resulting bivector has an area equal to the length of that sum of normals, and a “direction” perpendicular to that resulting normal.  This fun little Manipulate lets you interactively visualize this process, by changing the radius of a set of summed bivectors, each oriented in a different direction, and observing the effects of doing so.

Of course, you can interpret this visualization as nothing more than a representation of addition of cross products, if you were to interpret the vector representing a cross product as an oriented area with a normal equal to that cross product (where the normal’s magnitude equals the area, as in this bivector addition visualization.)  This works out nicely because of the duality relationship between the cross and wedge product, and the duality relationship between 3D bivectors and their normals.

Spinor solutions with alternate \( \gamma^0 \) representation.

January 2, 2019 phy2403 No comments , ,

[Click here for a PDF of this post with nicer formatting]

This follows an interesting derivation of the \( u, v \) spinors [2], adding some details.

In class (QFT I) and [3] we used a non-diagonal \( \gamma^0 \) representation
\begin{equation}\label{eqn:spinorSolutions:20}
\gamma^0 =
\begin{bmatrix}
0 & 1 \\
1 & 0
\end{bmatrix},
\end{equation}
whereas in [2] a diagonal representation is used
\begin{equation}\label{eqn:spinorSolutions:40}
\gamma^0 =
\begin{bmatrix}
1 & 0 \\
0 & -1
\end{bmatrix}.
\end{equation}
This representation makes it particularly simple to determine the form of the \( u, v \) spinors. We seek solutions of the Dirac equation
\begin{equation}\label{eqn:spinorSolutions:60}
\begin{aligned}
0 &= \lr{ i \gamma^\mu \partial_\mu – m } u(p) e^{-i p \cdot x} \\
0 &= \lr{ i \gamma^\mu \partial_\mu – m } v(p) e^{i p \cdot x},
\end{aligned}
\end{equation}
or
\begin{equation}\label{eqn:spinorSolutions:80}
\begin{aligned}
0 &= \lr{ \gamma^\mu p_\mu – m } u(p) e^{-i p \cdot x} \\
0 &= -\lr{ \gamma^\mu p_\mu + m } v(p) e^{i p \cdot x}.
\end{aligned}
\end{equation}
In the rest frame where \( \gamma^\mu p_\mu = E \gamma^0 \), where \( E = m = \omega_\Bp \), these take the particularly simple form
\begin{equation}\label{eqn:spinorSolutions:100}
\begin{aligned}
0 &= \lr{ \gamma^0 – 1 } u(E, \Bzero) \\
0 &= \lr{ \gamma^0 + 1 } v(E, \Bzero).
\end{aligned}
\end{equation}
This is a nice relation, as we can determine a portion of the structure of the rest frame \( u, v \) that is independent of the Dirac matrix representation
\begin{equation}\label{eqn:spinorSolutions:120}
\begin{aligned}
u(E, \Bzero) &= (\gamma^0 + 1) \psi \\
v(E, \Bzero) &= (\gamma^0 – 1) \psi
\end{aligned}
\end{equation}
Similarly, and more generally, we have
\begin{equation}\label{eqn:spinorSolutions:140}
\begin{aligned}
u(p) &= (\gamma^\mu p_\mu + m) \psi \\
v(p) &= (\gamma^\mu p_\mu – m) \psi
\end{aligned}
\end{equation}
also independent of the representation of \( \gamma^\mu \). Looking forward to non-matrix representations of the Dirac equation ([1]) note that we have not yet imposed a spinorial structure on the solution
\begin{equation}\label{eqn:spinorSolutions:260}
\psi
=
\begin{bmatrix}
\phi \\
\chi
\end{bmatrix},
\end{equation}
where \( \phi, \chi \) are two component matrices.

The particular choice of the diagonal representation \ref{eqn:spinorSolutions:40} for \( \gamma^0 \) makes it simple to determine additional structure for \( u, v \). Consider the rest frame first, where
\begin{equation}\label{eqn:spinorSolutions:160}
\begin{aligned}
\gamma^0 – 1 &=
\begin{bmatrix}
1 & 0 \\
0 & -1
\end{bmatrix}

\begin{bmatrix}
1 & 0 \\
0 & -1
\end{bmatrix}
=
\begin{bmatrix}
0 & 0 \\
0 & 2
\end{bmatrix} \\
\gamma^0 + 1 &=
\begin{bmatrix}
1 & 0 \\
0 & -1
\end{bmatrix}
+
\begin{bmatrix}
1 & 0 \\
0 & -1
\end{bmatrix}
=
\begin{bmatrix}
2 & 0 \\
0 & 0
\end{bmatrix},
\end{aligned}
\end{equation}
so we have
\begin{equation}\label{eqn:spinorSolutions:280}
\begin{aligned}
u(E, \Bzero) &=
\begin{bmatrix}
2 & 0 \\
0 & 0
\end{bmatrix}
\begin{bmatrix}
\phi \\
\chi
\end{bmatrix} \\
v(E, \Bzero) &=
\begin{bmatrix}
0 & 0 \\
0 & 2
\end{bmatrix}
\begin{bmatrix}
\phi \\
\chi
\end{bmatrix}
\end{aligned}
\end{equation}
Therefore a basis for the spinors \( u \) (in the rest frame), is
\begin{equation}\label{eqn:spinorSolutions:180}
u(E, \Bzero) \in \setlr{
\begin{bmatrix}
1 \\
0 \\
0 \\
0
\end{bmatrix},
\begin{bmatrix}
0 \\
1 \\
0 \\
0
\end{bmatrix}
},
\end{equation}
and a basis for the rest frame spinors \( v \) is
\begin{equation}\label{eqn:spinorSolutions:200}
v(E, \Bzero) \in \setlr{
\begin{bmatrix}
0 \\
0 \\
1 \\
0
\end{bmatrix},
\begin{bmatrix}
0 \\
0 \\
0 \\
1
\end{bmatrix}
}.
\end{equation}
Using the two spinor bases \( \zeta^a, \eta^a \) notation from class, we can write these
\begin{equation}\label{eqn:spinorSolutions:220}
\begin{aligned}
u^a(E, \Bzero) &=
\begin{bmatrix}
\zeta^a \\
0
\end{bmatrix},
\qquad
v^a(E, \Bzero) &=
\begin{bmatrix}
0 \\
\eta^a \\
\end{bmatrix}.
\end{aligned}
\end{equation}

For the non-rest frame solutions, [2] opts not to boost, as in [3], but to use the geometry of \( \gamma^\mu p_\mu \pm m \). With their diagonal representation of \( \gamma^0 \) those are
\begin{equation}\label{eqn:spinorSolutions:240}
\begin{aligned}
\gamma^\mu p_\mu – m
&=
p_0
\begin{bmatrix}
1 & 0 \\
0 & -1
\end{bmatrix}
+
p_k
\begin{bmatrix}
0 & \sigma^k \\
– \sigma^k & 0
\end{bmatrix}

m
\begin{bmatrix}
1 & 0 \\
0 & 1
\end{bmatrix}
=
\begin{bmatrix}
E – m & – \Bsigma \cdot \Bp \\
\Bsigma \cdot \Bp & -E – m
\end{bmatrix} \\
\gamma^\mu p_\mu + m
&=
p_0
\begin{bmatrix}
1 & 0 \\
0 & -1
\end{bmatrix}
+
p_k
\begin{bmatrix}
0 & \sigma^k \\
– \sigma^k & 0
\end{bmatrix}
+
m
\begin{bmatrix}
1 & 0 \\
0 & 1
\end{bmatrix}
=
\begin{bmatrix}
E + m & – \Bsigma \cdot \Bp \\
\Bsigma \cdot \Bp & -E + m
\end{bmatrix} \\
\end{aligned}
\end{equation}

Let’s assume that the arbitrary momentum solutions \ref{eqn:spinorSolutions:140} are each proportional to the rest frame solutions
\begin{equation}\label{eqn:spinorSolutions:300}
\begin{aligned}
u^a(p) &= (\gamma^\mu p_\mu + m) u^a(E, \Bzero) \\
v^a(p) &= (\gamma^\mu p_\mu – m) u^a(E, \Bzero).
\end{aligned}
\end{equation}
Plugging in \ref{eqn:spinorSolutions:240} gives
\begin{equation}\label{eqn:spinorSolutions:320}
\begin{aligned}
u^a(p) &=
\begin{bmatrix}
(E + m) \zeta^a \\
(\Bsigma \cdot \Bp ) \zeta^a
\end{bmatrix} \\
v^a(p) &=
\begin{bmatrix}
(\Bsigma \cdot \Bp) \eta^a \\
(E + m) \eta^a
\end{bmatrix},
\end{aligned}
\end{equation}
where an overall sign on \( v^a(p) \) has been dropped. Let’s check the assumption that the rest frame and general solutions are so simply related
\begin{equation}\label{eqn:spinorSolutions:340}
\begin{aligned}
\lr{ \gamma^\mu p_\mu – m } u^a(p)
&=
\begin{bmatrix}
E – m & – \Bsigma \cdot \Bp \\
\Bsigma \cdot \Bp & -E – m
\end{bmatrix}
\begin{bmatrix}
(E + m) \zeta^a \\
(\Bsigma \cdot \Bp ) \zeta^a
\end{bmatrix} \\
&=
\begin{bmatrix}
(E^2 – m^2 – \Bp^2) \zeta^a \\
0
\end{bmatrix} \\
&= 0,
\end{aligned}
\end{equation}
and
\begin{equation}\label{eqn:spinorSolutions:360}
\begin{aligned}
\lr{ \gamma^\mu p_\mu + m } v^a(p)
&=
\begin{bmatrix}
E + m & – \Bsigma \cdot \Bp \\
\Bsigma \cdot \Bp & -E + m
\end{bmatrix}
\begin{bmatrix}
(\Bsigma \cdot \Bp ) \eta^a \\
(E + m) \eta^a \\
\end{bmatrix} \\
&=
\begin{bmatrix}
0 \\
\Bp^2 + m^2 – E^2
\end{bmatrix} \\
&= 0.
\end{aligned}
\end{equation}
Everything works out nicely. The form of the solution for this representation of \( \gamma^0 \) is much simpler than the Chiral solution that we found in class. We end up with an explicit split of energy and spatial momentum components in the spinor solutions, instead of factors involving \( p \cdot \sigma \) and \( p \cdot \overline{\sigma} \), which are arguably nicer from a Lorentz invariance point of view.

References

[1] C. Doran and A.N. Lasenby. Geometric algebra for physicists. Cambridge University Press New York, Cambridge, UK, 1st edition, 2003.

[2] Claude Itzykson and Jean-Bernard Zuber. Quantum field theory. McGraw-Hill, 1980.

[3] Michael E Peskin and Daniel V Schroeder. An introduction to Quantum Field Theory. Westview, 1995.

Final first draft of complete notes for UofT PHY2403, QFT I .

December 27, 2018 phy2403 No comments , ,

I’ve now uploaded a new version of my class notes for PHY2403, the UofT Quantum Field Theory I course, taught this year by Prof. Erich Poppitz.

This update adds notes for all remaining lectures (up to and including lecture 23.)  I’ve made a pass with a spellchecker to correct some of the aggregious spelling erorss, and also redrawn three figures, replacing photos, which cuts the size in half!

I’ve posted the redacted version (316 pages).  The full version, with my problem set solutions (including errors) is 409 pages.

Feel free to contact me for the complete version (i.e. including my problem set solutions, with errors) of any of these notes, provided you are not asking because you are taking or planning to take this course.

Contents:

  • Preface
  • Contents
  • List of Figures
  • 1 Fields, units, and scales.
  • 1.1 What is a field?
  • 1.2 Scales.
  • 1.2.1 Bohr radius.
  • 1.2.2 Compton wavelength.
  • 1.2.3 Relations.
  • 1.3 Natural units.
  • 1.4 Gravity.
  • 1.5 Cross section.
  • 1.6 Problems.
  • 2 Lorentz transformations.
  • 2.1 Lorentz transformations.
  • 2.2 Determinant of Lorentz transformations.
  • 2.3 Problems.
  • 3 Classical field theory.
  • 3.1 Field theory.
  • 3.2 Actions.
  • 3.3 Principles determining the form of the action.
  • 3.4 Principles (cont.)
  • 3.4.1 d = 2.
  • 3.4.2 d = 3.
  • 3.4.3 d = 4.
  • 3.4.4 d = 5.
  • 3.5 Least action principle.
  • 3.6 Problems.
  • 4 Canonical quantization, Klein-Gordon equation, SHOs, momentum space representation, raising and lowering operators.
  • 4.1 Canonical quantization.
  • 4.2 Canonical quantization (cont.)
  • 4.3 Momentum space representation.
  • 4.4 Quantization of Field Theory.
  • 4.5 Free Hamiltonian.
  • 4.6 QM SHO review.
  • 4.7 Discussion.
  • 4.8 Problems.
  • 5 Symmetries.
  • 5.1 Switching gears: Symmetries.
  • 5.2 Symmetries.
  • 5.3 Spacetime translation.
  • 5.4 1st Noether theorem.
  • 5.5 Unitary operators.
  • 5.6 Continuous symmetries.
  • 5.7 Classical scalar theory.
  • 5.8 Last time.
  • 5.9 Examples of symmetries.
  • 5.10 Scale invariance.
  • 5.11 Lorentz invariance.
  • 5.12 Problems.
  • 6 Lorentz boosts, generators, Lorentz invariance, microcausality.
  • 6.1 Lorentz transform symmetries.
  • 6.2 Transformation of momentum states.
  • 6.3 Relativistic normalization.
  • 6.4 Spacelike surfaces.
  • 6.5 Condition on microcausality.
  • 7 External sources.
  • 7.1 Harmonic oscillator.
  • 7.2 Field theory (where we are going).
  • 7.3 Green’s functions for the forced Klein-Gordon equation.
  • 7.4 Pole shifting.
  • 7.5 Matrix element representation of the Wightman function.
  • 7.6 Retarded Green’s function.
  • 7.7 Review: “particle creation problem”.
  • 7.8 Digression: coherent states.
  • 7.9 Problems.
  • 8 Perturbation theory.
  • 8.1 Feynman’s Green’s function.
  • 8.2 Interacting field theory: perturbation theory in QFT.
  • 8.3 Perturbation theory, interaction representation and Dyson formula.
  • 8.4 Next time.
  • 8.5 Review.
  • 8.6 Perturbation.
  • 8.7 Review.
  • 8.8 Unpacking it.
  • 8.9 Calculating perturbation.
  • 8.10 Wick contractions.
  • 8.11 Simplest Feynman diagrams.
  • 8.12 Phi fourth interaction.
  • 8.13 Tree level diagrams.
  • 8.14 Problems.
  • 9 Scattering and decay.
  • 9.1 Additional resources.
  • 9.2 Definitions and motivation.
  • 9.3 Calculating interactions.
  • 9.4 Example diagrams.
  • 9.5 The recipe.
  • 9.6 Back to our scalar theory.
  • 9.7 Review: S-matrix.
  • 9.8 Scattering in a scalar theory.
  • 9.9 Decay rates.
  • 9.10 Cross section.
  • 9.11 More on cross section.
  • 9.12 d(LIPS)_2.
  • 9.13 Problems.
  • 10 Fermions, and spinors.
  • 10.1 Fermions: R3 rotations.
  • 10.2 Lorentz group.
  • 10.3 Weyl spinors.
  • 10.4 Lorentz symmetry.
  • 10.5 Dirac matrices.
  • 10.6 Dirac Lagrangian.
  • 10.7 Review.
  • 10.8 Dirac equation.
  • 10.9 Helicity.
  • 10.10 Next time.
  • 10.11 Review.
  • 10.12 Normalization.
  • 10.13 Other solution.
  • 10.14 Lagrangian.
  • 10.15 General solution and Hamiltonian.
  • 10.16 Review.
  • 10.17 Hamiltonian action on single particle states.
  • 10.18 Spacetime translation symmetries.
  • 10.19 Rotation symmetries: angular momentum operator.
  • 10.20 U(1)_V symmetry: charge!
  • 10.21 U(1)_A symmetry: what was the charge for this one called?
  • 10.22 CPT symmetries.
  • 10.23 Review.
  • 10.24 Photon.
  • 10.25 Propagator.
  • 10.26 Feynman rules.
  • 10.27 Example: muon pair production
  • 10.28 Measurement of intermediate quark scattering processes.
  • 10.29 Problems.
  • A Useful formulas and review.
  • A.1 Review of old material.
  • A.2 Useful results from new material.
  • B Momentum of scalar field.
  • B.1 Expansion of the field momentum.
  • B.2 Conservation of the field momentum.
  • C Reflection using Pauli matrices.
  • D Explicit expansion of the Dirac u,v spinors.
  • D.1 Compact representation of
  • E Mathematica notebooks
  • Bibliography