Lecture 10 | String Theory and M-Theory

(November 30, 2010) Professor Leonard Susskind continues his discussion on T-Duality; explains the theory of D-Branes; models QFT and QCD; and introduces the application of electromagnetism.
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

[@TheJoyfulPianist]

This is such a privilege. Fight tooth and nail to keep these lectures on youtube. This is a type of video that is all too rare.

[@joabrosenberg2961]

T-duality; WInding number conservation 16:00; Radius compactification 25:00; Duality equations 33:00; Gravitational field attraction and repulsion (!) 39:00; Gravity in 5 dimensions 44:00; Kalb Ramond B field 1:00:00; D-Branes (duality for closed strings) 1:03:00; Dirichle-Neuman duality 1:13:00; 2-dimensional D-Branes 1:29:00; Magnetic monopoles 1:43:00

[@petergreen5337]

❤thank you

[@saikiranalvala502]

I can't thank you enough professor susskind..thanks a lot..u are a legend..and thanks a lot stanford university for providing such a valuable material for free...can't thank enough...it has been a privilige

[@xi7837]

I really like these videos because it gives anyone the opportunity to learn physics on a high level

[@machinesofadystopianfuture4059]

I want to know what cookies he eats. I went on a cookie eating rampage after watching these lectures.

[@WildAnimalChannel]

Thank you Professor Susskind!

[@vincentbutton5926]

I really enjoy these lecture sets. D-branes... just wow!

[@bushje]

astonishing. fascinating. a privilege to watch this series. thank you!!?

[@wosz1234]

Course Ended Thank you Standford and Mr Susskind!

[@aragorn0006]

Enjoyed this lecture. The last half hour of this lecture is really good. At last I understand why there is only 8 gluons.

[@otonanoC]

Viewer 1070 here. I hung on every word. Hoping for a lecture 11!

[@davidelm5401]

Truely amazing lecture series. I love every bit of it. If I could suggest anything, consider this: A 3 brane with holes in it. Something like a 3 d fishing net (mostly empty space). Color it red. Another (blue) 3 brane just like the red one but interleaved through out. Every vertex of the red brane connects through a string to the nearest vertex of the blue brane. Some springs or spongy material (the matmoss) between the branes provides a bit of pressure. Some rules apply to allow a small bit of motion.If a cosmic ray strikes a string or a node then a wave may travel in 2 opposite directions, twisting a red string around a blue one. (translation rules, etc) As the two twists travel far apart each maintains its twist in the two fields (which is why there MUST be two (or more)) branes here.) The twists provide opposite forces (charges) which will be attracted to each other. Also each twist provides a new deformation in the 2 fields which though weak, acts exactly like gravity (there's your "5th" dimension compaction).... more?--David A. Elm

[@quantamuon]

Leonard Susskind is awesome. I Love His Work.

[@petergreen5337]

❤Thank you very much Professor and class.

[@cloffff]

@luzzie9 Theres a big difference between explaining the very basics and explaining what motivates string theory as a physical model. And be sure, the motivations for it are very significant. If theorizing about what happens near the Planck scale sounds dubious, then just stick with standard quantum field theory. String theory exists to answer ambitious questions, and they will be ambitious no matter what theory is proposed to answer them.

[@TenzinLundrup]

21:40 The momentum of an unwound string in the y direction in n/r so it's orbital angular momentum is n/r*r = n. So the more basic fact is the quantization of orbital angular momentum.

[@nicodanny2112]

There's a spectacular chapter in Brian Greene's first book Elegant Universe that gives an awesome narrative description of winding number of strings in the compact dimensions and the inability to distinguish between a world in which r>>1 and r

[@brainoutyakabrainout]

Yeah, I keep imagining straws stuck in spacetime as if the latter were a magic wavy carpet, which to us would seem like in-place cyclones that never move. So they look like that, but act like pillars.

[@WALLACE9009]

Thanks. I couldn't stop watching!

[@astralmaster1692]

Thank you stanford

[@sherlockholmeslives.1605]

This is where it takes my sheer brain power to comprehend such things! Lol! I wish I had some!!

[@kevinegan1400]

First of all a big thanks to Stanford University and Professor Susskind for making such an amazing set of truly enlightning educational videos available to the public for free. I have a few comments that come to mind after watching. 1. It might be a bit simplistic to just talk of strings as one dimensional but I know that we must walk before we can run. 2.At least one of the extra proposed dimensions might be a large dimension possibly infinite in extent. This could then be similar to the bulk space of the Ekpyrotic brane theory of Steinhardt and Turoc. 3.In some future time if humanity doesn't eome extinct then there may be some technological means of extracting a space ship from our three brane and using the bulk space as a means of traversing large interstellar distances by avoiding the effects of relativity that apply when moving through our three brane. A different approach than the Alcubierre warp drive that requires huge quantities of exotic negative energy that may well not actually exist. It is interesting how we can go from using a theory where brane are submerged in a bulk space or subspace to describe the properties of subatomic particles in the micro universe to using it to speculate on future methods of space travel in the macro universe. All very speculative of course but interesting in that some of it may well become fact.

[@PMaldeev]

From what prof. said you can't have D-branes higher than 6, for 3 dimensions are ordinary noncompactified space and strings are allowed to move freely along these directions. I guess.

[@navjot5717]

U duality is the best understood example of the link between strong coupling, integrability, and the AdS/CFT correspondence. There are two versions of SU(2) super Yang-Mills. One is the usual SYM which is well understood at strong coupling. The other is the so-called ABJM theory. (Which is where U duality and M theory actually meet) It has no superpotential and is believed to have weak-coupling dynamics similar to that of pure N=4 SYM. At first sight, the two theories seem to be completely different. However, in both theories, the dynamics of the theory is entirely determined by duality of SU(2).

[@Recaustic]

I havnt watched all of this but does it cover bosonic string theory?

[@balasubr2252]

Could we not have two dimensions of time, with different orientations? One going left, another right or one going clockwise and another anti-clockwise or one going forward and another going backward?

[@johnqpublic2718]

Bala Subramanian simply, no

[@buttegowda]

Curious : Where does 1/137 fit in string theory ? Is this number predicted by any of these equations as coupling constant between two 'particles' held by the 'spring' for the lack of better word/phrase ? I think any string/mtheory which can somehow come up with this is very important.

[@etiennealive]

Thanks for posting !

[@brendawilliams8062]

100559503 x 1001032 to a 10066.. is a lot of stretching both sides twice?

[@kevinldonnelly]

What the difference between D-Branes with photons and D-Branes with gluons, are they not both the same D3-Branes

[@sherlockholmeslives.1605]

Kevin Donnelly WHAAAT! I failed trying to read an abridged children's version of 'Black Beauty' ( 1877 ) by Anna Sewell ( 1820 - 1878 ). I absolutely f**king love being completely lost by minds and knowledge far beyond my own! Did you know that Nelson's Column in London is 169ft high? In the 1980's when I was a kid I used to watch open university and loved those brain boxes coming out with mind blowing intellectual knowledge that I couldn't grasp in the slightest bit! Is Max Tegmark the most intelligent person alive?! I have been to Oxford and Cambridge as a sight seer and to Oxford on holiday with my parents and have felt the lost contentment I could have if only I was clever! I know some key names and their dates and a bit of info about brilliant people and some poems from memory but my highest grade at school was a D in English Literature in my GCE's and I got another GCE D in English from college. I am thick and I am HAPPY!

[@frankdimeglio8216]

@@sherlockholmeslives.1605 WHY ELECTROMAGNETISM/ENERGY IS UNIFIED AND BALANCED WITH/AS WHAT IS GRAVITY: Gravity AND ELECTROMAGNETISM/ENERGY are LINKED AND BALANCED opposites, AS ELECTROMAGNETISM/ENERGY IS GRAVITY. Therefore, Einstein's equations and Maxwell's equations are unified (given the addition of a fourth spatial dimension); AS E=mc2 is DIRECTLY and fundamentally derived from F=ma; AS TIME DILATION proves that electromagnetism/ENERGY IS GRAVITY. ACCORDINGLY, Einstein's equations predict that SPACE is expanding OR contracting in and with TIME; AS ELECTROMAGNETISM/ENERGY IS GRAVITY. GREAT !!! (Very importantly, outer "space" involves full inertia; AND it is fully invisible AND black.) Gravity/acceleration involves BALANCED inertia/INERTIAL RESISTANCE, AS ELECTROMAGNETISM/ENERGY IS GRAVITY. Accordingly, the rotation of the Moon MATCHES it's revolution. "Mass"/ENERGY involves BALANCED inertia/INERTIAL RESISTANCE consistent WITH/as what is BALANCED electromagnetic/gravitational force/ENERGY, AS ELECTROMAGNETISM/ENERGY IS GRAVITY. Accordingly, objects fall at the SAME RATE (neglecting air resistance, of course); AS ELECTROMAGNETISM/ENERGY IS GRAVITY. Gravity IS ELECTROMAGNETISM/ENERGY. A PHOTON may be placed at the center of what is THE SUN (as A POINT, of course), AS the reduction of SPACE is offset by (or BALANCED with) the speed of light; AS ELECTROMAGNETISM/ENERGY IS GRAVITY. Energy has/involves GRAVITY, AND ENERGY has/involves inertia/INERTIAL RESISTANCE. THE SUN purely exemplifies time DILATION. INSTANTANEITY is FUNDAMENTAL. Time DILATION proves that electromagnetism/ENERGY IS GRAVITY, AS E=mc2 is DIRECTLY and fundamentally derived from F=ma. "Mass"/ENERGY IS GRAVITY. ELECTROMAGNETISM/ENERGY IS GRAVITY. Gravity/acceleration involves BALANCED inertia/INERTIAL RESISTANCE, AS ELECTROMAGNETISM/ENERGY IS GRAVITY. GREAT !!! The stars AND PLANETS are POINTS in the night sky. Let's compare this directly with BOTH a falling object AND the speed of light (c). Great. E=mc2 IS F=ma. Gravity/acceleration involves BALANCED inertia/INERTIAL RESISTANCE, AS ELECTROMAGNETISM/ENERGY IS GRAVITY. GRAVITATIONAL force/ENERGY IS proportional to (or BALANCED with/as) inertia/INERTIAL RESISTANCE, AS ELECTROMAGNETISM/ENERGY IS GRAVITY. Gravity IS ELECTROMAGNETISM/ENERGY. This NECESSARILY represents, INVOLVES, AND describes what is possible/potential AND actual IN BALANCE. Time DILATION proves that electromagnetism/ENERGY IS GRAVITY, AS E=mc2 is DIRECTLY and fundamentally derived from F=ma. INSTANTANEITY is FUNDAMENTAL to the FULL and proper understanding of physics/physical experience. Ultimately and truly, TIME is possible/potential AND actual IN BALANCE; AS ELECTROMAGNETISM/ENERGY IS GRAVITY. The ultimate unification of physics/physical experience combines, BALANCES, AND includes opposites, AS ELECTROMAGNETISM/ENERGY IS GRAVITY. GREAT. It ALL makes perfect sense. THINK !!! The Earth that undergoes time DILATION IS thus represented (ON BALANCE) as what is A POINT in the night sky, AS ELECTROMAGNETISM/ENERGY IS GRAVITY. (So, notice that the BLUE SKY IS no longer visible. Think.) E=mc2 IS F=ma. It is FULLY proven. Gravity IS ELECTROMAGNETISM/ENERGY. ELECTROMAGNETISM/ENERGY IS GRAVITY. Alas, the INTEGRATED EXTENSIVENESS of THOUGHT (AND description) is improved in the truly superior mind. I have truly, CLEARLY, AND MATHEMATICALLY unified physics/physical experience. OVERLAY what is THE EYE in BALANCED RELATION to/WITH what is THE EARTH. (Notice the black space of THE EYE, AND the DOME of a person's eye is ALSO visible.) THE EARTH is ALSO blue. Again, E=mc2 IS F=ma. The stars AND PLANETS are POINTS in the night sky. Time dilation proves that E=mc2 is DIRECTLY and fundamentally derived from F=ma, AS electromagnetism/ENERGY IS GRAVITY. It ALL makes perfect sense. Gravity IS ELECTROMAGNETISM/ENERGY. ELECTROMAGNETISM/ENERGY IS GRAVITY. BALANCE AND completeness go hand in hand. By Frank DiMeglio

[@Paul1239193]

he never covered M-theory

[@iphgfqweio]

No Professor, As I will go on the rubber band, I will never forget to go in the Y direction. Yours, Sigma.

[@kevinldonnelly]

What would the D-brane model of a hydrogen atom look like?

[@bohanxu6125]

I would guess it would look like two one-end-anchored strings. Each has only one anchor on the D3-Brane while the other end stretches out to "infinity". Two such one-anchor string have two different orientations so one is positive charge while the other is negative charge. They exchange two-anchor string on the D3-brane. The exchange of two-anchor string is the exchange of photon. For those two one-end-anchored string, the other ends of them stretching out, not really to infinity, but to different other 3-Brane which describe whether they are proton or electron. The D-brane models here explain here only describe the photon (QED) or WZ boson filed (QCD). This is why the charge string stretch out to "infinity". For instance, one side of this string manifest as charge that interact with the one D3-Brane that describe the photon-aspect of the string while the other side of this string connects to some other D3-Brane that describe electron-aspect of the string.

[@loren-emmerich]

Fibonacci says 1,1,2,3,5,8..etc. but then 4 must also exist (1+1+2=4) Think of a four clover.

[@peterpalumbo3644]

As to time can the two dimensions of same be time forward and time backward and all the dimensions superimposed on the space or probability space together, something like the disk area of a black hole that can also be a white hole.

[@goph999]

I am sure that I can give a lecture and saying what ever I want, and the audiance saying woow. Have you ever read about the "Emperor's New Clothes?" by HC Andersen?

[@sherlockholmeslives.1605]

goph999 I'll stick with heavier objects falling faster than lighter ones! Although they do in a vacuum. Plato's ( 429bc - 347bc ) 'Wax Tablet Hypothesis' and Aristotle's ( 384bc - 322bc ) 'Theory of Everything' are about my scientific level!

[@lauriepocock3066]

Partway through watching this series of excellent series of lectures I was thinking could dimension's really be degrees of freedom, but we saw Prof Susskind was not enamoured of that view, but after watching this last lecture I wonder if a brane could equate to levels of potential? and if so, would there be a discrete paritcle (I know it's not the right word), for all, is it 24, 12, or 9 dimensions? (are they jaffa cakes?)

[@brainoutyakabrainout]

Yeah, I'd think so too. Dimensions of potential reality should 'attach' somehow to what really happens, and then the potential is available. For there necessarily are potentials the are secondary to any of the allotted potentials on the 'real' planes operating. But if potential only, then not real until certain combinations of conditions occur. So not real prior and not real yet but can be real: else there's no capacity for what he would call 'evolving'.

[@zxrxrichter4471]

🙏

[@vilmossapi674]

Nice.

[@TheGrahamBrechin]

I'm viewer 762 :) still hanging in there Professor

[@brendawilliams8062]

Yeah, I do that too and circle back to my previously unlearned remarks.

[@nurlatifahmohdnor8939]

Page 633 tendon = A thick strand or sheet of tissue that attaches a muscle to a bone. Tendons consist of *collagen fibres and are therefore inelastic: they ensure that the force exerted by muscular contraction is transmitted to the relevant part of the body to be moved. tendon = o-tot kick = ten-dang

[@vuurdraak5650]

Thanks for all the public lectures, I will now go and watch the angular momentum of my chocolate chip cookie and try to taste the vibration of its yummy multidimensional strings melting on my tongue :)

[@Dilaton100]

Ha ha, now I`ve see all 10 of them :-D As Lenny Susskind says, You can call me g55 LOL Many happy thanks for this GREAT course

[@loren-emmerich]

E in mc2 should be part of string theory, that's what i think while having a sinus infection in my head.

[@loren-emmerich]

Is dark energie E-string theory?

[@PMaldeev]

No puns in this one INCIDENTALLY.

[@peterpalumbo3644]

The parts of 'M' Theory are gone into but no mention is made of actual M of F Theory.

[@ever_lord]

I think there is a following season there : kzbin.info/www/bejne/hIuQdp-pq75-r9E

[@davidwilkie9551]

After 6min.. the instantaneous "snapshot" = Black-body Singularity positioning-> Observation, implies the (Circular Slide Rule type) Correspondence with Superspin and the spiralling Embedding Theorm of phase-locked holography, in which the "Rubber Band" is ONE-Infinity superspiralling in 0-1-2-ness, 2D String in Theoretical unity-connection, (self-defining => Uncertainty Principle of logarithmic Factoring), alternately superimposed in 0-1-2-3-4-etc QM-TIME Supersymmetric e-Pi-i condensation vertices in vortices, compounded in time duration timing sync-duration crystallisation matrix, ..the connectivity function by i-reflection containment, and aligned in Fluxion-Integral Temporal superposition, ..tuning-probabilities of AM-FM time-timing, continuous creation connection cause-effect, = i-reflection timing-spacing modulation.., the Universal Clockwork, Holographic Principle Imagery, Polar-Cartesian self-defining infinitesimal Calculus, a self-defining projection-drawing Actuality of QM-TIMESPACE Logarithmic Time Communication In-form-ation. Ie Pictured Inflation Condensation here-now-forever continuous creation-emanation, featuring implied potential log-antilog brane, tangency horizons of spin-spiral shearing shockwave=> 2-ness sum-of-all-histories here-now-forever, Perspective. A Rose by any other name will smell as Sweet, and the Theoretical Connection cause-effect has the same multiphase-locked elemental function ->artistic arrangements in Correspondence Completeness. Math-Physics Analysis discoveries are still worth recognition by Peers, but "Everything is Theoretical" Nomenclatures require constant updating, past-future discoveries are reintegration proportioning probability quantization, superposition identification Measurement Problem, re-evaluation situation. "Don't throw the baby, (eg BBT), out with the Bathwater" of deeper repositioning In-form-ation Advances, (as in this Lecture), of Cosmological Objects.

[@EdSmiley]

I don't expect you to follow every detail... whew... :)

[@aelabassi]

what kind of cookies he eat ,i want some for finishe this luctures.

[@frankdimeglio8216]

WHY ELECTROMAGNETISM/ENERGY IS UNIFIED AND BALANCED WITH/AS WHAT IS GRAVITY: Gravity AND ELECTROMAGNETISM/ENERGY are LINKED AND BALANCED opposites, AS ELECTROMAGNETISM/ENERGY IS GRAVITY. Therefore, Einstein's equations and Maxwell's equations are unified (given the addition of a fourth spatial dimension); AS E=mc2 is DIRECTLY and fundamentally derived from F=ma; AS TIME DILATION proves that electromagnetism/ENERGY IS GRAVITY. ACCORDINGLY, Einstein's equations predict that SPACE is expanding OR contracting in and with TIME; AS ELECTROMAGNETISM/ENERGY IS GRAVITY. GREAT !!! (Very importantly, outer "space" involves full inertia; AND it is fully invisible AND black.) Gravity/acceleration involves BALANCED inertia/INERTIAL RESISTANCE, AS ELECTROMAGNETISM/ENERGY IS GRAVITY. Accordingly, the rotation of the Moon MATCHES it's revolution. "Mass"/ENERGY involves BALANCED inertia/INERTIAL RESISTANCE consistent WITH/as what is BALANCED electromagnetic/gravitational force/ENERGY, AS ELECTROMAGNETISM/ENERGY IS GRAVITY. Accordingly, objects fall at the SAME RATE (neglecting air resistance, of course); AS ELECTROMAGNETISM/ENERGY IS GRAVITY. Gravity IS ELECTROMAGNETISM/ENERGY. A PHOTON may be placed at the center of what is THE SUN (as A POINT, of course), AS the reduction of SPACE is offset by (or BALANCED with) the speed of light; AS ELECTROMAGNETISM/ENERGY IS GRAVITY. Energy has/involves GRAVITY, AND ENERGY has/involves inertia/INERTIAL RESISTANCE. THE SUN purely exemplifies time DILATION. INSTANTANEITY is FUNDAMENTAL. Time DILATION proves that electromagnetism/ENERGY IS GRAVITY, AS E=mc2 is DIRECTLY and fundamentally derived from F=ma. "Mass"/ENERGY IS GRAVITY. ELECTROMAGNETISM/ENERGY IS GRAVITY. Gravity/acceleration involves BALANCED inertia/INERTIAL RESISTANCE, AS ELECTROMAGNETISM/ENERGY IS GRAVITY. GREAT !!! The stars AND PLANETS are POINTS in the night sky. Let's compare this directly with BOTH a falling object AND the speed of light (c). Great. E=mc2 IS F=ma. Gravity/acceleration involves BALANCED inertia/INERTIAL RESISTANCE, AS ELECTROMAGNETISM/ENERGY IS GRAVITY. GRAVITATIONAL force/ENERGY IS proportional to (or BALANCED with/as) inertia/INERTIAL RESISTANCE, AS ELECTROMAGNETISM/ENERGY IS GRAVITY. Gravity IS ELECTROMAGNETISM/ENERGY. This NECESSARILY represents, INVOLVES, AND describes what is possible/potential AND actual IN BALANCE. Time DILATION proves that electromagnetism/ENERGY IS GRAVITY, AS E=mc2 is DIRECTLY and fundamentally derived from F=ma. INSTANTANEITY is FUNDAMENTAL to the FULL and proper understanding of physics/physical experience. Ultimately and truly, TIME is possible/potential AND actual IN BALANCE; AS ELECTROMAGNETISM/ENERGY IS GRAVITY. The ultimate unification of physics/physical experience combines, BALANCES, AND includes opposites, AS ELECTROMAGNETISM/ENERGY IS GRAVITY. GREAT. It ALL makes perfect sense. THINK !!! The Earth that undergoes time DILATION IS thus represented (ON BALANCE) as what is A POINT in the night sky, AS ELECTROMAGNETISM/ENERGY IS GRAVITY. (So, notice that the BLUE SKY IS no longer visible. Think.) E=mc2 IS F=ma. It is FULLY proven. Gravity IS ELECTROMAGNETISM/ENERGY. ELECTROMAGNETISM/ENERGY IS GRAVITY. Alas, the INTEGRATED EXTENSIVENESS of THOUGHT (AND description) is improved in the truly superior mind. I have truly, CLEARLY, AND MATHEMATICALLY unified physics/physical experience. OVERLAY what is THE EYE in BALANCED RELATION to/WITH what is THE EARTH. (Notice the black space of THE EYE, AND the DOME of a person's eye is ALSO visible.) THE EARTH is ALSO blue. Again, E=mc2 IS F=ma. The stars AND PLANETS are POINTS in the night sky. Time dilation proves that E=mc2 is DIRECTLY and fundamentally derived from F=ma, AS electromagnetism/ENERGY IS GRAVITY. It ALL makes perfect sense. Gravity IS ELECTROMAGNETISM/ENERGY. ELECTROMAGNETISM/ENERGY IS GRAVITY. BALANCE AND completeness go hand in hand. By Frank DiMeglio

[@rmerkle1]

Type "True Theory of Everything Quadrant Model of Reality 1" into KZbin for the Truth.

[@ivanjelenic5627]

please, I'm not listening for hours to some idiots that can barely form coherent sentences and string two logical thoughts together