1. 04/12/07Journal Club / Vibrating Turtles1 Irrefutable Theory of Vibrating Turtles Journal Club April 12, 2007 Peter Mendygral

2. 04/12/07Journal Club / Vibrating Turtles2 Irrefutable Theory of Vibrating Turtles Greene, B., 1999, The Elegant Universe Hedrich, R., 2006, “String Theory – From Physics to Metaphysics”, arXiv:physics/0604171 Woit, Peter., 2006, Not Even Wrong Schwarz, J., 2007, “String Theory – Progress and Problems”, arXiv:hep-th/0702219v2

3. 04/12/07Journal Club / Vibrating Turtles3 Outline Brief History Current Status Predictions What Is It?

4. 04/12/07Journal Club / Vibrating Turtles4 Twisted History 1921: Kaluza-Klein Theory –E&M can be combined with gravity if a 4 th spatial dimension is added 1968-1974: Dual Resonance Model –Simultaneously developed by Y. Nambo, H. Nielsen, and L. Susskind as an interpretation of the strong interactions of scattering particles –Uses Euler β-function to give scattering amplitudes –Solutions resemble modes of an oscillating string

5. 04/12/07Journal Club / Vibrating Turtles5 Twisted History 1971: Supersymmetry Introduced –Symmetry between fermions and bosons –Proposed in particle physics to solve fine tuning issues –Also proposed in string theory when fermions were added 1970s: Gravity “Discovered” in String Theory –Accidental production of massless, spin-2 graviton –Combining gravity and supersymmetry => supergravity = (something I fear, like Jackson)

6. 04/12/07Journal Club / Vibrating Turtles6 Twisted History 1984: The “Big Year” –Normalizations and cancellation of a few infinities rids string theory of “anomalies” Now incorporates parity violations Symmetry is restored in small symmetry breaking limit –String theory now considered candidate to describe all elementary particles –Requirement that 6 extra spatial dimensions exist (for symmetry reasons)

7. 04/12/07Journal Club / Vibrating Turtles7 Twisted History Calabi-Yau Manifolds –Needed to get extra 6 dimensions, keeping 3 we know of, and enable non-zero fluxes of fields (e.g. magnetic) through space –Fold extra dimensions onto generalized Calabi-Yau Manifolds of 6 dimensions –Part of the problem with the theory today, there’s thousands and likely more of these

8. 04/12/07Journal Club / Vibrating Turtles8 M-Theory (a.k.a. “Magic-Theory”) 1995 Edward Witten unveiled conjectures that 5 existing string theories were all descriptions of one theory –Side note, Witten briefly attended UW- Madison as graduate student in economics and had aspirations of being a political writer He proposed they were all manifestations of one theory, “M-Theory”

9. 04/12/07Journal Club / Vibrating Turtles9 M-Theory (a.k.a. “Magic-Theory”) M-Theory is not well defined as a theory Supposedly non-perturbative version of superstring theory Theorists would like it to: –Be unique (avoid the 10 500 potential vacua) Pick a specific Calabi-Yau shape Get rid of the landscape problem –Calculate from first principles the 105 extra parameters in supersymmetric standard model –Save the environment and end the War No evidence that any of this is will happen

10. 04/12/07Journal Club / Vibrating Turtles10 M-Theory Branes Of All Types This new version requires higher dimensional entities than 1D strings Strings with open ends need a boundary on which to vibrate –p-branes, p is some number of dimensions –D-branes, membranes derived from Dirichlet boundary conditions for open strings –Observable universe defined by 3D D-brane evolving in time in 10 dimensional space This is purely speculative

11. 04/12/07Journal Club / Vibrating Turtles11 What Can String Theory Predict? Cosmological Constant –Each realized universe in string theory produces a new cosmological constant –Values more or less random –1/10 120 produce nearly the expected value –With ≥10 500 realizations there’s still a little too many to pick from –Not much predictive power there

12. 04/12/07Journal Club / Vibrating Turtles12 What Can String Theory Predict? Inflation –Mechanism would be D3-brane and anti-D3-brane colliding and annihilating –One scalar mode of an open string connecting the branes is the inflaton –Tension released in branes heats up the Universe and many new strings are produced –Cosmic superstrings Tension so small they have avoided detection Discovery of linear lensing may reveal them

13. 04/12/07Journal Club / Vibrating Turtles13 What Can String Theory Predict? Hawking Radiation –The absence of a real theory of quantum gravity prevents checking how this would work in a consistent theory –For certain specially chosen backgrounds, string theory can predict the occurrence of Hawking radiation –Of course not for physical black holes in 4 visible dimensions

14. 04/12/07Journal Club / Vibrating Turtles14 What Can String Theory Predict? Large Hadron Collider –Perhaps we may see some black holes created with properties suggested by string theory –Non-detection wouldn’t rule it out

15. 04/12/07Journal Club / Vibrating Turtles15 Current Status Over 30 years of effort –Lots of papers (7404 found on SPIRES alone as of 04/11/07) –~23 graduate programs –Hundreds of active theorists –Books, NOVA & Science Channel programs, plenty of popular articles The “only game in town” (except Loop Quantum Gravity)

16. 04/12/07Journal Club / Vibrating Turtles16 Current Status Not one testable experimental prediction –Only can describe phenomena already described by other theories –Anthropic principle often invoked to avoid landscape issue Problem is not with the theory, it’s how nature is Leonard Susskind

17. 04/12/07Journal Club / Vibrating Turtles17 Is It Even Science? Is it mathematics? –Peter Woit would say, “Certainly not!” Math requires rigorous proofs of theorems via well defined constructs Is it physics? –Theorists not active in string theory would say it’s more like math –Lacks experimental/physical motivation

18. 04/12/07Journal Club / Vibrating Turtles18 Is It Even Science? Is it faith? –Harvard PhD John Hagelin would say yes Distinguished physicist with plenty of well cited papers Now identifies unified superstring theory with that of the Maharishi’s “unified field of consciousness” –Michio Kaku “The mind of God is music resonating in 11-dimensional hyperspace.” –String theory often defended with the phrase: “…you can’t falsify string theory, not yet.”

19. 04/12/07Journal Club / Vibrating Turtles19 Is It Even Science? The theory is a “set of hopes that a theory exists” Can it be falsified? –Philosopher Karl Popper proposed science is: An explanation that can be used to make a falsifiable prediction “It’s turtles all of the way down.”

20. 04/12/07Journal Club / Vibrating Turtles20 Irrefutable Theory of Vibrating Turtles From Not Even Wrong : “…what if I decide to speculate that at sufficiently short distance scales, physics is to be described not in terms of particles, strings, etc., but in terms of turtles? …most people would say that I was not doing science. …if after a few months work I did manage to derive the parameters of the standard model from the turtle assumption, then people would have to change their minds…”

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