Lecture 6 | String Theory and M-Theory

(October 25, 2010) Leonard Susskind focuses on the different dimensions of string theory and the effect it has on the theory.
String theory (with its close relative, M-theory) is the basis for the most ambitious theories of the physical world. It has profoundly influenced our understanding of gravity, cosmology, and particle physics. In this course we will develop the basic theoretical and mathematical ideas, including the string-theoretic origin of gravity, the theory of extra dimensions of space, the connection between strings and black holes, the "landscape" of string theory, and the holographic principle.
This course was originally presented in Stanford's Continuing Studies program.
Stanford University:
www.stanford.edu/
Stanford Continuing Studies Program:
csp.stanford.edu/
Stanford University Channel on KZbin:
/ stanford

[@ruchi9917]

All in all, I can never thank enough Dr. Susskind for putting up these wonderful series which we all can access freely and in every part of the world. Thanks a ton :D

[@joabrosenberg2961]

Scattering; Mandelstam variables 28:00; Feynman diagrams 29:30; Veneziano amplitude 40:00; Worldsheets 48:00; Euler beta function 1:10:00;

[@jonnymahony9402]

thx for doing this on almost every lecture, very helpful

[@user-fc8xw4fi5v]

This man is a legend for making such highly academic material so accessible to the layman. I've been able to follow along this entire journey so far, witnessing the beauty of string theory firsthand, armed only with my knowledge of high school math and the principle of least action.. all thanks only to Mr Susskind's wonderful explanations and analogies! I wish I could give these lecture videos 2 thumbs up!

[@ce6535]

Thank you Stanford and Dr. Susskind for making these videos available. I wish I had known about them 4 years sooner.

[@kyuteh]

Holy crap I was able to tell that the Veneziano amplitude was a beta function before he derived it. I feel smart for once in this lecture series. haha :P

[@NothingMaster]

Today’s students are so incredibly lucky and privileged to have access to all these marvelous lectures from first rate professors and universities for free. You could practically do a Ph. D. program in physics by watching videos on KZbin. In our days we had to essentially figure all that stuff out on our own.

[@lucasthompson1650]

9 down votes? I didn't know Hawking had that many grad students.

[@slyy4096]

1 year later, still only 9 Downs...

[@nikhilkrishna233]

Now 10

[@maxwellsequation4887]

Its 10 now, these 10 enemies of beauty.

[@arsal09]

May you live long! :)

[@perjespersen4746]

Still going strong

[@petergreen5337]

❤Thank you very much Professor and class.

[@WHATSONAUSTRALIANOW]

The Fineman - pretty much a persons social habits of meetng people by a small to wide berth. Get outdoor to find the magic, outside your comfort zones.... Great explanation Proff

[@JimmyGray]

Still cant believe i asked him for this lecture but had to work in the ER in Montana so i missed it. He was like you missed the lecture you asked for:)

[@tataltsal]

43:50 Veneziano amplitude = Euler Beta function!

[@erwinmarschall2465]

1:14:00 One has to consider e.g. Γ(-s) which has poles for s=0,1,2, ...

[@siquod]

When the two strings join, the momenta of the point masses that make up the combined string will be discontinuous and thus the higher harmonics of the string will be excited. These excitations will in general persist when the string separates again, so that the outgoing particles have some amplitude of having a higher rest mass than the ingoing ones, i.e. it's an inelastic collision. A string with an excited high enough higher harmonic will even be heavy enough to form a black hole. Does that mean that every time two particles collide there should be a small amplitude for them to form one or more black holes of a few Planck masses? Of course, the black holes would have to be virtual unless the collision energy is very high. So maybe at low energies the highly excited string states interfere destructively when integrating over the different possible durations that the strings are joined, and so the outgoing particles have probability 1 to be in the first excited state? He didn't show the details of how to arrive at the Veneziano amplitude and so I can't tell whether that only says something about elastic collisions or also about inelastic ones where the outgoing particles have different rest masses from the ingoing ones.

[@frun]

I think that particles are a collective phenomena (for example vortex tube rings) in 3D space

[@peterpalumbo3644]

With Regards To below, higgs particle decays into two bottom quarks not top quark. Decay into photons has also been observed,

[@BPHAbishekP]

top quark decay is most probable as higgs particle decay into particles with huge mass

[@BuckMcH]

He was sloppy on the math but still I have enjoyed the series.

[@harrycraig2077]

BuckMcH I agreee

[@angelmorales2241]

Mire ha mi y tengo halgo ke exponer sobre Hoyente local y su fuersa meno cuando duerme y fuersa mas al sentire descubierto (esto tiene Apellido o X conponente ) un ofisina de ufolojia se puede denunsiar primer caso y cual Pais

[@csmcmillion]

@arsal09 May he live long and Popper!

[@shannonmortenson2254]

First , let’s just get that I am crazy out of the way. I need to know more about M-string theory. Like every living thing has cells , every person and every animal has a face but why not trees bushes snow clouds fire water . Well these particles who make a face , I think they are pulling out of the cell Quarks. My wolf wand about 50 people I’ve met that can see these things in M theory and we are not scientists or mathematicians, but we know what we are seein so we need help with this and maybe we can help each other

[@saikiranalvala502]

18:00

[@harrycraig2077]

Interesting but confusing

[@djehutisundaka7998]

He never mentions the fact that 's' and 't' stand for 'space' and 'time'. The s-channel and the t-channel represent particle transformations through space and time which he shows to exhibit symmetry. From a relativistic perspective, this should not be a surprise. He never explains the conclusion of harmonic oscillators being the physical description of it all but rather simply begins with it. String theory simply defines particles by their oscillations thereby reducing them to being one-dimensional strings. There is no observable justification for this and seems to naturally result in a world that requires hidden superpartner particles, imperceivable compactified dimensions, and other unknowable features to make up for an unjustifiable conclusion.

[@setcohomology6979]

You explain everything except string theory

[@slyy4096]

String theory needed Feynman before physics of it became just maths

[@peterpalumbo3644]

Brookhaven National Lab says CERN has found that the Higgs Boson decays into the Top Quark, This may help explain how particles put on mass.

[@dizznizz314]

NO

[@ugaugauga488]

It's sad to see such powerful minds go insane! Math has turned them into patients!

[@Iberedmas]

Before you teach be sure what you are doing!!

[@slyy4096]

people who can not build or trade or anthing valuable, teach it