Phy107Spr06Lect40 - Final Exam String theory M on d a y , M...

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1 Phy107 Lecture 40 1 Wed. May 3, 2006 Final Exam • Monday, May 8: 2:45 - 4:45 pm 2241 Chamberlin • Note sheet: two double-sided pages • Cumulative exam-covers all material, 40 questions – 11 questions from exam 1 material – 12 questions from exam 2 material – 11 questions from exam 3 material – 6 questions from post-exam 3 material Study Hint : download blank hour exams from web site and take them closed-book, with note sheet only. In-class review: Friday, May 5 in class Phy107 Lecture 40 2 Wed. May 3, 2006 String theory • A string is a fundamental quantum mechanical object that has a small but nonzero spatial extent. • Just like a particle has a mass, a string has a ‘tension’ that characterizes its behavior. • Quantum mechanical vibrations of the string correspond to the particles we observe Phy107 Lecture 40 3 Wed. May 3, 2006 •Strings can vibrate in different ways For example: Guitar string Different vibration Different sound! •Fundamental string Different vibration Different particles! electron photon graviton What are these strings? We describe them only in terms of a fundamental tension – as for a rubber band How big are they? A particle of energy E has a wavelength E = h c / λ = 1240 eV-nm / λ So can probe down to scales of order λ …. So far we’re down to much less than the size of atomic nucleus… strings could be 10 19 times smaller! T Phy107 Lecture 40 5 Wed. May 3, 2006 Types of strings There are two basic types of strings: open and closed But the natural interactions of strings is via their endpoints - strings join together when their endpoints touch. Open strings can be come closed strings. Phy107 Lecture 40 6 Wed. May 3, 2006 String Interactions • Strings interact by joining and splitting 2 strings joined split into 2
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2 Phy107 Lecture 40 7 Wed. May 3, 2006 Back to the ends Different ‘boundary conditions’ for the ends of the strings. Anchored to the sides of the small dimensions (branes) Graviton cannot be anchored - it is an excitation of a closed string (with no ends). Behaves differently Phy107 Lecture 40 8 Wed. May 3, 2006 Some problems • Strings are collections of points — an infinite number of points • Much more complex behavior than ‘points’.
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This note was uploaded on 01/05/2012 for the course PHYS 107 taught by Professor N/a during the Spring '08 term at Wisconsin.

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Phy107Spr06Lect40 - Final Exam String theory M on d a y , M...

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