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Quarks and Strings

Quarks and Strings. “On a remarkable connection between quark physics & string theory…”. Nick Evans. Theory Group. The Rule of Three. Everything is made of just three things!. Electrons Protons Neutrons. Previously.

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Quarks and Strings

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  1. Quarks and Strings “On a remarkable connection between quark physics & string theory…” Nick Evans Theory Group

  2. The Rule of Three Everything is made of just three things! • Electrons • Protons • Neutrons Previously You have heard about electrons changing orbits & emitting or absorbing energy

  3. Quarks! Protons and neutrons are made from up and down quarks The Strong Force The strong force binds the quarks together & then the protons together.. Remarkably it gets stronger with quark separation

  4. Confinement You can never pull hard enough to liberate a quark from a proton… The Vacuum The attractive force between quarks is so strong that binding energy >> mass energy The vacuum has lower energy if it fills itself with quark anti-quark pairs! Interaction energy provides proton mass

  5. Quantum Chromodynamics - QCD There are three identical colours of each quark… and “glue” fields that allow them to probe each other’s colour The glue fields have properties of two quarks…

  6. Computers needed! Chris & Jonathan Gravitational & Electrical Orbits are well behaved QCD orbits are much harder to control

  7. String Theory A quark pair can look like a string BUT String theory lives in 9 spatial dimensions Short strings have the charge of two quarks so are glue fields Closed strings describe gravity fields This is not QCD (surely?) but an interesting possible theory of everything….

  8. The Cat is Out! Membranes too… and 3-branes… and… In string theory branes emerge as areas of space where strings have their ends tied

  9. String Dual of QCD The open strings tied to a 3-brane make up a theory of QCD glue fields in 3 spatial dimensions Maldacena conjectured that the remaining strings in 9 dimensions provide an alternative description of QCD

  10. Quarks Too To have quarks as well we need to anchor one end of the strings somewhere else eg on a 7-brane The mass of the quark is given by the minimum length of the string energy = length x tension

  11. To get massless quarks the 7-brane & 3-brane should intersect A simple (one page) calculation shows that the branes repel – they prefer to generate a dynamical quark mass Babington, Erdmenger, NE, Erlich, Zuralnik, 2003

  12. Health Warning We’re still describing the basic features of QCD… we’re using maths tricks which mean we are not yet calculating real QCD quantities…. The new framework & understandings are exciting though!

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