Thursday 28 December 2017

Particle Physics Reading list update

This is an update to a previous post written many years ago for those who want to understand modern particle physics. This is aimed at those readers who have a basic knowledge of undergraduate physics such as those who have completed the Open university quantum physics course SM358 and are comfortable with the marhematical techniques given in that course. Unfortunately the Open University doesn't go much further and so students of the Open university are left high and dry if they want to understand the excitement of particle physics. 

Particle physics can be understood at a basic level by extending Fermi's Golden rule for time dependent perturbation theory to relativistic equations of motion in particular the Dirac equation. This is some what surprising given that most postgraduate courses in particle physics launch the student in the deep end by starting with quantum field theory. So that the impression is given that one must wade through many pages and pages of abstract formalism before getting to the stage where one can actually study particle physics. Whilst eventually understanding quantum field theory is important for those who want to do actual research or at least understand what is going on. As a first step I would reccomend the reader to stick with the approach based on Fermi's Golden rule. To that end my current reccomendation for the best introduction to particle physics is given by the first two books in the list. These two books will give the reader a basic understanding of what a Feynman diagram is, how to use Feynman diagrams to calculate the quantities of interest to particle physics such as particle decay rates and scattering cross sections and how numerous experiments and calculations led to the development of the Standard Model of particle physics. 


  1)     Modern Particle Physics Mark Thomson Cambridge University Press 2013

 There is an associated web site with summaries of each chapter given to his Cambridge students and also hints and solutions to many of the problems. 


Another (older book) which covers some topics in more detail at the same level as Thomson is

2)     Quarks and Leptons: An Introductory course in Modern Particle Physics  F Halzen and A Martin John Wiley and Sons 1984

It is a testimony to the robustness of the Standard Model of particle physics that a book published 33 years ago is still relevant to today.

The above two books should be enough for most people who want to gain a working knowledge of the Standard model of particle physics, without getting bogged down in the intricacies of quantum field theory. Having said that there is no doubt that quantum field theory is one of the foundations of modern physics, so for those who want to begin a lifes time journey to understand quantum field theory then the best starting point (IMHO) is

3)     Student Friendly Quantum Field theory Robert D Klauber Sandtrove Press 2013

Whilst this book only covers quantum electrodynamics, and the so called canonical formalism it does so in great detail, filling in alll the gaps (or at least most of them) and includes an introduction to renormalisation theory and how to do 1 loop calculations (the meat of quantum field theory). Again there is an associated web site


The next step which covers both QCD and the Weinberg Salam Model from a field theory perspective in some detail is this book

4)     Quantum Field Theory 2nd Edition Franz Mandl and Graham Shaw Wiley 2010

Finally for those who want graduate level textbooks which will take the reader up to the stage of postgraduate research then my two current favourites are

5)     An introduction to Quantum Field theory Peskin and Schroeder Perseus Books 1995

This book has 3 research projects at the end of each section, culminating in an investigation of the properties of the Higg’s boson (It is my ambition to try and attempt these some time)

A more modern text book is

6)     Quantum Field theory and the Standard Model M D Schwartz Cambridge 2014

The above two books, unless one is really dedicated, are probably best seen as reference books, as it will take the reader pages and pages of algebra to fill in the details. With such books it is probably best to focus on repeating one or two calculations in detail and accept the rest on trust.

Finally a good survey of the experimental foundations of particle physics which includes many original papers is

7)     The Experimental Foundations of Particle Physics R Cahn and G Goldhaber  Cambridge 2009

I hope this helps  I am near the end of completing a particle physics calculation on elastic electron proton scattering and its experimental confirmation, as a preliminary to umderstanding the inelastic scattering which led to the development of the quark model and our current understanding of the theory of the strong interaction. I will post details of this calculation in the next post. Unfortunately Drop box is no longer supporting public acccess to files which means that some of the links I have posted to my work, no longer work. I will try and find a work around. If not then I can post the files to anyone who contacts me via my  e-mail address chrisf19572002@yahoo.co.uk It only remains for me to wish all my readers and followers a happy new year and good luck if you are studying for any Open University or other course.

Sunday 15 October 2017

Quantum Biology much ado about noting

First apologies for not posting for a while I did not finish S383 the third TMA was a nightmare all waffle and no maths. A very disappointing course my reccomendation for those who want a mathematical based course is to avoid this one like the plague. Anyway I am now on restricted status which means under the new regulations I can't take any more OU courses unless I apply for removal from my restricted status. I did manage to salvage something namely I had built up enough credits for a second open degree without honours. If I want an honours degree in mathematics then I would have to take a new 1st level course in Statistics, another 1st level course and the second level course in mathematical methods. I can't really see me taking this so that would appear to be the end of my open university studies

Anyway I digress the main focus of this post is on the allegedly new science of quantum biology the claim has been made that biological systems exhibit all the mysterious effects associated with quantum mechanics such as non-locality, entanglement and bose Einstein condensation a short overview of these claims is given by Jim Al Khalili (Who I would have thought known better but I guess he has to get his money from somewhere and how better than to jump on a bandwagon)

https://www.google.co.uk/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&uact=8&ved=0ahUKEwjp2K27hvPWAhWIChoKHYr6Dz4QtwIIKDAA&url=https%3A%2F%2Fwww.ted.com%2Ftalks%2Fjim_al_khalili_how_quantum_biology_might_explain_life_s_biggest_questions&usg=AOvVaw2SeqAMJK9gfXHM97NcUGMU


I have severe doubts about the whole thrust of this (as those who have read my earlier posts on quantum mechanics might have guessed)

Just a few points

a) It is highly surprising that phenomenon such as Bose Einstein condensation occur at room temperatures usually such effects manifest themselves at very low temperatures. The wet noisy enviroment associated with biological systems would seem to mitigate against this

b) The fact that experiments seem to have established long range electron coherence in photo-synthesis and other similar processes should not necessarily be seen as evidence for non-locality, the conditions in which so called entanglement occur and violation of the Bell inequalities are usually quite specific involving the emission of two particles from a common source such that their net angular momentum is zero. In photosynthesis there would appear to be no such initial conditions

c) Khalili and others make the common fallacy of assuming that the so called wavefunction is a physical entity and not as the Born interpretation would have effectively the square root of a probability density function or probability amplitude whose modulus squared gives rise to a probability density function. Thus the pictures that Khalili show of quantum tunneling are pictures of a probability density function not of an electron or other particle spread out over all space.

d) Quantum superposition is not an actual superposition but a superposition of possible states. The idea that some people have that before a measurement is made a quantum system is in a state of limbo which collapses to one of the possible states on measurement is misleading to say the least. Before measurement the observer does not know which one of the many possible states the system will be found in. He or she can only assign certain probabilities in accordance with the physical setup On measurement the system will be found to be in one of those states and so the superposition of possibilities 'collapses' to the one found on measurement. If the experiment is repeated a sufficiently large number of times then the system will have been found in each one of the states in accordance with the probabilities initially assigned. However because of the random nature of quantum events I can never tell by a single measurement what state the system will be found in.

e) The above interpretation simplifies all the agonising over the Aspect experiment. On the above interpretation a given observer A at his or her station will either measure a particle to have spin up or down. However once A has done this he or she will immediately know the result of B's measurement But of course as B has no way of knowing what A's measurement is then as far as he is concerned his particle could still be measured with spin up or spin down. There is no faster than speed of light communication caused by A's affecting B's particle.

So for all those reasons even if it were true that biological systems are exhibiting the so called mysterious aspects of quantum mehcanics. There is a perfectly rational explanation based on a purely statistical interpretation of quantum mechanics. Particles do not split in two when passing through slits, Particles do not traverse all possible paths at once and there is definitely no faster than light communication between separated quantum systems.

However recent experiments have caused doubt on whether or not the long correlation times observed in photosynthesis are due to quantum effects.

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5559008/

A good overview of how photosynthesis is modelled is given by this MSc thesis which again shows that there is no need to invoke the mysterious aspects of quantum mechanics to explain the electron coherence.

https://arxiv.org/abs/1503.03277

Also this web site is the blog of a condensed matter physicist who has been very sceptical about the quantum biology bandwagon

http://condensedconcepts.blogspot.co.uk/

So for all the above reasons I think it is safe to say that the Quantum biology bandwagon is truly much ado about nothing