Hope all of you had a good holiday and a good start to the New Year!
I myself continue to be extraordinarily busy as we move into 2015, but I am glad to say that some of that activity involves communicating science to the public. In fact, a week from today I will be giving a public talk — really a short talk and a longer question/answer period — in Cambridge, just outside of Boston and not far from MIT. This event is a part of the monthly “CafeSci” series, which is affiliated with the famous NOVA science television programs produced for decades by public TV/Radio station WGBH in Boston.
Note for those of you have gone before to CafeSci events: it will be in a new venue, not far from Kendall Square. Here’s the announcement:
Tuesday, January 20th at 7pm (about 1 hour long)
Le Laboratoire Cambridge (NEW LOCATION)
http://www.lelaboratoirecambridge.com/
650 East Kendall St, Cambridge, MA
“The Large Hadron Collider Restarts Soon! What Lies Ahead?”
Speaker: Matthew Strassler
“After a long nap, the Large Hadron Collider [LHC], where the Higgs particle was discovered in 2012, will begin operating again in 2015, with more powerful collisions than before. Now that we know Higgs particles exist, what do we want to know about them? What methods can we use to answer our questions? And what is the most important puzzle that we are hoping the LHC will help us solve?”
Public Transit: Red line to Kendall Square, walk straight down 3rd Street, turn right onto Athenaeum Street, and left onto East Kendall
Parking: There is a parking deck – the 650 East Kendall Street Garage – accessible by Linskey Way.
34 Responses
Apologies for interrupting myself, but I need to know if a quantum wave function can exist in isolation, i.e, not entangled with anything. Thanks!
Is the spin reversed ie left-handed to right-handed? Are there any other bosons whose fields need to be described using complex numbers?
Your question isn’t well posed, because spin isn’t left or right handed. Chirality and Helicity can be handed, and the relationship between them takes two lectures in an advanced particle physics class. Helicity is about spin relative to motion. Chirality is more subtle and has to do with relativistic transformations. Helicity is defined for any particle with spin, but is observer-dependent. Chirality is not observer-dependent, but is only defined for spin 1/2 fermions. Chirality and helicity are the same for massless spin 1/2 fermions. A fermion’s antiparticle has the opposite chirality, but only has the opposite helicity if it is massless; otherwise its helicity is observer-dependent and it makes no sense to specify it. Yes, this is confusing.
W bosons (positive and negative charge) can have helicity +1, -1 or 0 (also called Left, Right and Longitudinal.) But this is observer-dependent and so it isn’t a fundamental property of the particle, unlike its charge or its rest-mass, which is observer-independent.
Many other bosons are described with complex numbers, though none of the others are known elementary particles. If supersymmetry were right, all of the spin-zero superpartners of the quarks and leptons would be described in this way.
Wow. I have a lot more reading to do! Thanks a million for pointing me in the right direction.
Well, thank you for your good questions. Can you tell me, are you a student, and if so at what stage? What’s your math background.
I’m a bus driver. I left school after my O-levels; I would have loved to continue to higher education, but I had to get a job.
I’ve been looking online for a good physics forum – this is the first time I’ve got any really helpful answers. As you can surely tell, I was getting a bit out of my depth in the above discussion!
I have many questions about black holes that I’ve been wanting to ask an expert, Recent developments in Loop Quantum Cosmology seem to have interesting consequences for black hole theory and possibly for Big Bang theory too. Do you cover those topics, or do you know of a site that does?
I was wondering if in the case of W bosons not all of the internal quantum numbers are reversed, as they are with electron/positron.
No, they are all reversed, except the ones that don’t reverse in the electron-positron case too, such as the overall spin and the mass.
Thanks for your help! It’s opened up a lot of lines of enquiry for me which will hopefully fill in some gaps. My lack of math skills is always going to prevent me having a real understanding of the theoretical physics behind it all – I guess I’m realistically aiming for an enhanced layman’s understanding of the broad concepts. I’ll keep chipping away at it.
Update: Although informed by ‘science’ documentaries that the Higgs boson gives everything mass (sic), I’ve just found out that the Higgs field’s interaction with quarks and electrons only accounts for @ 20 MeV of the mass of a @ 1 GeV hydrogen atom, which indirectly answers a lot of my questions about photons – wahoo!
Re W bosons: I was looking at the Standard Model diagram and noticed that the W was shown with a charge of +/-1, but the electron only shown as -1. So it is not showing antiparticles, cos the positron +1 isn’t shown. In which case, for the logic to be consistent, showing W as +/-1 implies an antiW with a charge of -/+1. That would seem to mean that, for example, in the Feynman diagram for Beta minus decay, you could replace the W- bosn with an “antiW+” boson and it wouldn’t make any difference.
You’re referring to my Standard Model diagram, or to another one? You’re right, that’s a fundamental inconsistency. Good point.
I found the SM diag on physics.stackexchange.com – I’m trying to understand the difference between definitions of mass.
The diagram suits most purposes when one isn’t trying to really understand things in detail. But you’re going deeper than the diagram can show.
You are so right about my ideas being a bit muddled! I’d got the impression that it’s all about conservation: that bosons can be produced singly but fermions only in particle-antiparticle pairs.
Re: W bosons – according to Prof G. Taylor (works on Atlas detector at Cern ) W+ & W- bosons only differ by charge and are not actually antiparticles of each other. He seems a legit source.
You mention complex numbers; I don’t really understand how describing something using imaginary numbers works. I read that time works like a spatial dimension when described using imaginary numbers, which helped me understand how the Universe can be finite but unbounded, but I didn’t get why i-numbers make time behave like space.
I do get that particles are ripples in fields, though.
I see. This is probably due to a semantic ambiguity in the term “anti-particle”. Professor Taylor probably has a particular notion in mind which focuses on the properties of fermions, namely that you can’t make a fermion without making an anti-fermion, whereas you can make a boson on its own. But Professor Taylor, as an experimentalist, is missing important theoretical points that would lead theorists to still say that the W+ is the antiparticle of the W-. I’d have to talk to him directly to figure out why he made this choice. Note, however, that the physics is the same, no matter how you describe it. The important thing is that W+ and W- behave just like any particle/anti-particle class — just like an electron and a positron, or a quark and an antiquark of the same “flavor”, a W+ and W- can annihilate to (or be created by) other particles that are their own anti-particles, such as photons.
I should also have mentioned that it isn’t yet clear whether neutrinos are their own antiparticles or not. That’s a subtle point having to do with where their masses come from.
Yes, my description of why one needs imaginary numbers in this context is correct, but pedagogically almost useless. I need to find a way to do a better job, and I will think about it.
You’re right, I have a terrible info source: the internet. Following your advice, I’ve now found out that only fermions and leptons have antiparticles – how could I not have found that out before! That’s the problem with autodidacticism – you end up with huge holes in your knowledge cos you’re not studying systematically. This is a great website for someone like me, very helpful. Expect more dumb questions soon!
Sadly yes, the internet as a whole is not a good source; you need to be highly selective. In my case I’m a professor of physics with 25 years of experience publishing papers in the field — and my goal is to communicate not my personal ideas but those of the mainstream in particle physics.
One detail: your notions of antiparticles, fermions and leptons are a little bit muddled still. The precise way to talk about antiparticles is this.
For any type of particles, there is another type of particle that is its “anti-particle”. But often the anti-particle and the particle are the same type of particle.
Any electrically charged particle has an anti-particle which is different from itself, because the charge changes from positive to negative or vice versa. This includes W particles, which are charged, but are bosons not fermions; also they are not leptons. Similarly, it includes pion particles, which are also bosons.
Even some neutral particles are different from their anti-particles. A neutron [a fermion] is made from three quarks. Its antiparticle is made from three antiquarks. So neutrons and anti-neutrons are different.
By contrast, photons don’t have a different type of particle as their anti-particle.
The source of the difference between neutral particles that have separate antiparticles and those that don’t isn’t about whether they are fermions or leptons or anything that you’ve heard of. Instead, it’s more subtle, and not obvious.
Specifically, some of these particles are ripples in fields that are described by ordinary “real” numbers. [Examples are electric fields, gravitational fields, Higgs fields, etc.] For these particles [photons, gravitons, Higgs particles], their anti-particles are of the same type.
Others are ripples in fields described by “complex” numbers. [Examples are neutrino fields, W fields, quark fields…] Those have a different type of particle as their anti-particle.
I have read that there is an antihiggs field – does it give mass to antimatter particles eg positrons? I would also like to know if it might be theoretically possible to cancel or block the effect of the higgs field so that matter wouldn’t interact with it and gain mass in the normal way – I’m thinking about a possible effect on inertia. Also, am I right in thinking that, since it arises through the interaction of a matter particle and the higgs field, mass is actually an emergent phenomenon?
This is wrong. There is no anti-Higgs field. You had a terrible information source. Please stick only to sources that are experts in the subject with proper credentials — otherwise you will be subjected to a huge amount of crap. Examples of people with credentials: Sean Carroll, Tomaso Dorigo, Seth Lenz, Resonaances (Adam Falkowski), Sabine Hossenfelder, … there are some others, but CHECK THE CREDENTIALS.
The Planck Consortium has now published new analyses of data returned by the eponymous space telescope. The telescope on board of the Planck satellite has measured the distribution of the cosmic microwave background radiation (CMB), which, in essence, tells us what the Universe looked like about 400,000 years after the Big Bang. These latest findings are in complete agreement with the predictions of Viatcheslav Mukhanov ’s theory – for example, his calculation of the value of the so-called spectral index of the initial inhomogeneities. As Jean-Loup Puget, Principal Investigator for the HFI-instrument on the Planck satellite, stated: “The Planck data confirm the basic predictions that quantum fluctuations are at the origin of all structures in the Universe.” Mukhanov, who first published his model in 1981 and joined the Physics Faculty at Ludwig-Maximilian University in Munich in 1997, says “I couldn’t hope for a better verification of my theory.”
http://www.esa.int/Our_Activities/Space_Science/Planck/Planck_reveals_first_stars_were_born_late
What is incorrect in mainstream physics today is the notion dark matter is a clump of stuff traveling with matter.
Dark matter is now understood to fill what would otherwise be considered to be empty space.
‘Cosmologists at Penn Weigh Cosmic Filaments and Voids’
“Dark matter … permeate[s] all the way to the center of the voids.”
‘No Empty Space in the Universe –Dark Matter Discovered to Fill Intergalactic Space’
“A long standing mystery on where the missing dark matter is has been solved by the research. There is no empty space in the universe. The intergalactic space is filled with dark matter.”
Dark matter which fills ’empty’ space is otherwise known as the aether. Aether has mass, physically occupies three dimensional space and is physically displaced by the particles of matter which exist in it and move through it. Including ‘particles’ as large as galaxies and galaxy clusters.
In the following two articles the aether is what waves in a double slit experiment.
‘From the Newton’s laws to motions of the fluid and superfluid vacuum: vortex tubes, rings, and others’
“This medium, called also the aether, has mass and is populated by the particles of matter which exist in it and move through it” …
… and displace it.
‘EPR program: a local interpretation of QM’
“Wave particle duality is described as the compound system of point particle plus accompanying wave (in the æther).”
A moving particle has an associated aether displacement wave. In a double slit experiment the particle travels through a single slit and the associated wave in the aether passes through both.
Q. Why is the particle always detected traveling through a single slit in a double slit experiment?
A. The particle always travels through a single slit. It is the associated wave in the aether which passes through both.
Why is mainstream physics in denial of understanding in a double slit experiment it is the dark matter that waves?
I appreciate your sense of humor!
Every major attempt at resolving the measurement problem seems to be saddled with some fundamental flaw despite decades of work on the issue.
Copenhagen: Infinite regress of observers, incoherent in cosmological scenarios
Many-Worlds: It can be shown that only the Born rule is consistent with unitary evolution, but actually getting the Born rule out requires circular reasoning
De Broglie/Bohm: No backreation on the wave function evolution by the “real” state of the system, which makes it hard to distinguish metaphysically from Many-Worlds (like Many-Worlds it treats the wave function as a physical object despite its potentially unlimited number of dimensions)
The feeling I get is that there’s some fundamentally wrong assumption somewhere that’s so subtle or unintuitive to grasp that no-one has ever been able to pin it down.
I am not referring to de Broglie-Bohm theory. I am referring to de Broglie’s double solution theory. In de Broglie’s double solution theory there are two waves. There is the physical wave which guides the particle and the wave-function wave which is statistical, non-physical and is used to determine the probabilistic results of experiments.
In de Broglie’s double solution theory it is the physical wave which guides the particle.
All physics needs to do is to understand particles of matter move through and displace the dark matter and all of the nonsense associated with mainstream physics is resolved.
In a double slit experiment it is the dark matter that waves.
http://physics.aps.org/articles/v8/6
Viewpoint: Do Quantum Superpositions Have a Size Limit?
George C. Knee, NTT Basic Research Laboratories, NTT Corporation, 3-1 Morinosato-Wakamiya, Atsugi, Kanagawa 243-0198, Japan
Published January 20, 2015 | Physics 8, 6 (2015) | DOI: 10.1103/Physics.8.6
Everyday experience tells us that big objects—eggs and humans—do not appear to exist in a superposition of states like that possible for more quantum objects, such as electrons. Does this mean quantum physics fundamentally doesn’t apply to objects beyond a certain size? A new experiment that allows the motion of a large atom in an optical lattice to be tracked could help in the search for a size cutoff. Using this setup, Carsten Robens at the University of Bonn, Germany, and his colleagues demonstrated that a cesium atom travels in a truly nonclassical fashion, moving as a quantum superposition of states and thus occupying more than one distinct location at a time [1]. Larger objects have been observed to have such inherently quantum properties, but the observation of Robens et al. is based on a stringent test considered to be the gold standard for confirming that a superposition exists. As such, their experiment constrains theories of physics that aim to replace quantum mechanics. Their technique could also be used to test superpositions on even more macroscopic scales, such as with larger atoms or molecules.
Have a good talk….Your site is much appreciated by the layperson interested in particle physics.
SuSy can’t ever be completely ruled out because it can hide at scales that may be theoretically impractical to ever probe. But natural SuSy is on the cusp of either being confirmed or ruled out. If natural SuSy is ruled out, it does not kill string theory.
Dr. Strassler : do you think that the EDM experiment by ACME rules out almost all of supersymmetry ?
I mean ruling out any hope that the second run of LHC will show any SUSY particles ?
Happy New Year, Matt!!
I have the same question as OakTree (@Class_of_78)
Happy New Year all, is it possible to make a reservation for the talk?
Happy New Year Professor, wish you and your colleagues a year full of discoveries and more questions, 🙂
BTW, for the upcoming talk, is it possible to link up, via the internet, those of us who live 903 km (I-90 west) away, :-)?
Hope you are will be continuing your discussion on the “triggering” component of the LHC experiments, I have a few questions which I touched on in an earlier article.
https://www.academia.edu/9835762/General_Relativity_Test_in_2015