Banner
Future Train Wreck: Mine or Modern Physics talk Next Thursday, Jan. 26

If you are in Cambridge, MA on Thursday, Jan. 26, you can see me live at MIT in room 3-270 from...

Holiday Physics Card, 2016

Just put them in the mail on December 24...It was a fun year of thinking, whether the idea is right...

Unified Mathematical Field Theory Talk

I gave a 15 minute talk at a local Americal Physical Society Meeting.  Here is the title and...

Holiday Card 2015

Here is my holiday card for 2015, a tradition of mine going back to 1990.  Enjoy.On the back...

User picture.
picture for David Hallidaypicture for Steve Schulerpicture for Helen Barrattpicture for Ladislav Kocbachpicture for Khalil Shakarchipicture for Amir D. Aczel
Doug SweetserRSS Feed of this column.

Trying to be a semi-pro amateur physicist (yes I accept special relativity is right!). I _had_ my own effort to unify gravity with other forces in Nature. It ran into quite a number of technically... Read More »

Blogroll

First I will play the old gauge symmetry game repeated everywhere for EM. I will then teach that old dog a new trick that ends up with the same bone. I will then struggle a little over the lingo to describe what I am interested in, the center of the quaternion group. I will then show how a new new trick, the new trick shifted to the right just enough to work, will lead to a gauge symmetry proof.


Let's review gauge symmetry in EM. Start with an arbitrary scalar function f. Take the conjugate of the 4-derivative operator and apply it to f:

Fire a machine gun at a wall with two slits. Look at the pattern bullets make that pass through. The pattern is the sum of two Gaussian curves. Classical physics makes sense.


Repeat the exercise with electrons or photons. Where there is constructive interference, the signal is strong. Where there is destructive interference, the signal can drop to zero. Waves behave that way all the time. Yet quantum interference works even if particles are fired at extremely low rates, such as once a day.

Dec. 6, Spinning the Interaction Story: Spin 1 (1 of 3)

Snarky puzzle
Figure out how to represent any quaternion using 3D rotations and one complex number.
Start the year off with a new toy model for gravity. It is a toy, so let's just play with it and see what we learn. Feel free in the comments section to vote if I should keep this toy or return it for a refund.

At a minimum, the toy must do three things. First, it must explain why I weigh a little over 150 pounds here on Earth. Second, it must explain why light bends in both time and space when flying by the edge of the Sun. Third, it needs to explain why I don't weigh over 300 pounds here on Earth, feeling only half the effects that light apparently does.

The more I read on this topic, the less confident I get. If you wish to read a solid technical explanation, I recommend a reply by David Simmons-Duffin sent to me by Henry. It all comes down to Lorentz invariance and unitarity when considering propagators.

In technical tales, if so much as one step is not understood, the path gets lost. I'll point out a few places where I get confused. He writes down the potential between two stationary particles for an arbitrary spin-L force carrier in momentum space:
Every year since 1990, I have made a holiday card sending it to friends and family (a list of ~ 50). They have always been nerdy. I try and feature something about the physics I figured out in the year. This one is less upbeat than those in the past, but there is a reason for that ;-)


Doug

No math, no snarky puzzle.

Next Monday/Tuesday, Dec 26, a vacation week.
Monday/Tuesday, Jan. 2/3: Spinning the Interaction Story: Attracting and Repelling.