Part I: Understanding String Theory

... To fully understand string theory is not a trivial endeavor. It is a synthesis of over a century of scientific advancement and draws from a wide variety of concepts familiar to physicists. String theory is often presented as a so-called grand unified theory (GUT); an attempt to describe the behavior ...

... To fully understand string theory is not a trivial endeavor. It is a synthesis of over a century of scientific advancement and draws from a wide variety of concepts familiar to physicists. String theory is often presented as a so-called grand unified theory (GUT); an attempt to describe the behavior ...

underdetermination and theory succession from the perspective of

... elementary particle physics model building is dominated by concepts which are either directly inspired by string theory, like the concept of large extra dimensions, or, like supersymmetry, gain authority from the claim that they are implied by string theory. Many recent cosmological models are also ...

... elementary particle physics model building is dominated by concepts which are either directly inspired by string theory, like the concept of large extra dimensions, or, like supersymmetry, gain authority from the claim that they are implied by string theory. Many recent cosmological models are also ...

Dimensional reasoning

... – Dimensionless equations and variable are independent of units. – Relative importance of terms can be easily estimated. – Scale (battleship or model ship) is automatically built into the dimensionless ...

... – Dimensionless equations and variable are independent of units. – Relative importance of terms can be easily estimated. – Scale (battleship or model ship) is automatically built into the dimensionless ...

The Internal and External Problems of String Theory

... that of a mathematically inspired metaphysics of nature? An adequate answer to these questions is certainly not to be expected from physics; physics does not have the methodology to answer such metatheoretical questions. These are undoubtedly questions to be answered in the context of philosophy of ...

... that of a mathematically inspired metaphysics of nature? An adequate answer to these questions is certainly not to be expected from physics; physics does not have the methodology to answer such metatheoretical questions. These are undoubtedly questions to be answered in the context of philosophy of ...

Superstring Theory and Empirical Testability - Philsci

... The consequences: Probably there does not exist any definitive catalogue of requirements for scientific theories, and especially for fundamental physical theories, which guarantees certainty with regard to an adequate description of nature. Every criterion can, in particular in isolation, be critici ...

... The consequences: Probably there does not exist any definitive catalogue of requirements for scientific theories, and especially for fundamental physical theories, which guarantees certainty with regard to an adequate description of nature. Every criterion can, in particular in isolation, be critici ...

Large Extra Dimensions - Are you sure you want to look at this?

... Aristotle thought about this idea. He concluded from physical experience that there are no physical objects described on manifolds of dimension greater than three. It was not until the 1850’s that the formalism to describe geometry of arbitrary dimension manifolds was created by Bernhard Riemann. Si ...

... Aristotle thought about this idea. He concluded from physical experience that there are no physical objects described on manifolds of dimension greater than three. It was not until the 1850’s that the formalism to describe geometry of arbitrary dimension manifolds was created by Bernhard Riemann. Si ...

F From Vibrating Strings to a Unified Theory of All Interactions

... gravity as one of the fluctuation modes of a closed string. Although it was not discovered exactly in this way, we can describe a logical path that leads to the discovery of gravity in string theory. One considers a string, similar in manyways to the vibrating strings with tension and mass that are ...

... gravity as one of the fluctuation modes of a closed string. Although it was not discovered exactly in this way, we can describe a logical path that leads to the discovery of gravity in string theory. One considers a string, similar in manyways to the vibrating strings with tension and mass that are ...

Recent Developments in String Theory

... or periodic (the fields change sign or not when transported around Σ), giving rise to fermionic or bosonic fields in space-time, respectively. It turns out that whenever the theory contains space-time fermions, it must have two dimensional supersymmetry, and this is why such string theories are call ...

... or periodic (the fields change sign or not when transported around Σ), giving rise to fermionic or bosonic fields in space-time, respectively. It turns out that whenever the theory contains space-time fermions, it must have two dimensional supersymmetry, and this is why such string theories are call ...

URL - StealthSkater

... Perhaps the most deeply entrenched common-sense notion about our World is that it is 3dimensional. It goes without saying that length, width, and breadth suffice to describe all objects in our visible universe. If we include time as another dimension, then 4 dimensions are sufficient to record all e ...

... Perhaps the most deeply entrenched common-sense notion about our World is that it is 3dimensional. It goes without saying that length, width, and breadth suffice to describe all objects in our visible universe. If we include time as another dimension, then 4 dimensions are sufficient to record all e ...

Superstring Theory

... • For the first time, physicists had a unified theory that could accommodate both Einstein’s explanation for gravity and the quantum explanation for particles and other forces. • To make the math work you needed several additional dimensions of space. Instead of a four-dimensional universe — three s ...

... • For the first time, physicists had a unified theory that could accommodate both Einstein’s explanation for gravity and the quantum explanation for particles and other forces. • To make the math work you needed several additional dimensions of space. Instead of a four-dimensional universe — three s ...

fundamental_reality\Black hole war

... In 1917, astronomer Karl Schwarzschild solved the equations of general relativity and rediscovered the dark star. Schwarzschild radius: the radius of an imaginary sphere within which light will be pulled into the dark star (or black hole.) The black hole itself is a “singularity”; ie a point in spac ...

... In 1917, astronomer Karl Schwarzschild solved the equations of general relativity and rediscovered the dark star. Schwarzschild radius: the radius of an imaginary sphere within which light will be pulled into the dark star (or black hole.) The black hole itself is a “singularity”; ie a point in spac ...

string theory: big problem for small size

... The original string theory developed in the period 1968–70 was known as bosonic string theory. The main disadvantages of this theory were: (i) it needs 26-dimensional space-time, (ii) the absence of fermions in the theory, and (iii) the existence of a particle with imaginary mass, called tachyon, ge ...

... The original string theory developed in the period 1968–70 was known as bosonic string theory. The main disadvantages of this theory were: (i) it needs 26-dimensional space-time, (ii) the absence of fermions in the theory, and (iii) the existence of a particle with imaginary mass, called tachyon, ge ...

Strings as hadrons

... that time. It was soon discovered by Yoichiro Nambu of the University of Chicago and myself (and in a slightly different form by Holger Bech Nielsen at the Niels Bohr Institute) that these amplitudes were the solution of a definite physical system that consists of extended 1D elastic strings. For th ...

... that time. It was soon discovered by Yoichiro Nambu of the University of Chicago and myself (and in a slightly different form by Holger Bech Nielsen at the Niels Bohr Institute) that these amplitudes were the solution of a definite physical system that consists of extended 1D elastic strings. For th ...

The Elegant Universe: Part 2

... NARRATOR: Obsession drives scientists to pursue the Holy Grail of physics, but are they ready for what they discover? Step into the bizarre world of the Elegant Universe right now. BRIAN GREENE: It's a little known secret but for more than half a century a dark cloud has been looming over modern sci ...

... NARRATOR: Obsession drives scientists to pursue the Holy Grail of physics, but are they ready for what they discover? Step into the bizarre world of the Elegant Universe right now. BRIAN GREENE: It's a little known secret but for more than half a century a dark cloud has been looming over modern sci ...

why do physicists think that there are extra dimensions

... a ~500 page proof that space and time are a priori however to make sense of quantum gravity, not to mention the Big Bang singularity, this cannot be true in the real theory of everything, spacetime should be emergent. ...

... a ~500 page proof that space and time are a priori however to make sense of quantum gravity, not to mention the Big Bang singularity, this cannot be true in the real theory of everything, spacetime should be emergent. ...

Ioan Muntean - International Society for the Advanced Study of

... later in string theory to add dimensions that capture interactions other than gravity. It is usually considered the conceptual starting point of string theory because it provides an answer to how the universe might have more than four dimensions.1 It is the hypothesis that the types of force in the ...

... later in string theory to add dimensions that capture interactions other than gravity. It is usually considered the conceptual starting point of string theory because it provides an answer to how the universe might have more than four dimensions.1 It is the hypothesis that the types of force in the ...

Gravity, Particle Physics and Their Unification 1 Introduction

... energy contained in the oscillations. When we view this oscillating string from far away, it looks like a pointlike object. These diﬀerent oscillatory states of the string are analogous to the diﬀerent polarization states of the particles. Note that the mass of the string state itself depends on the ...

... energy contained in the oscillations. When we view this oscillating string from far away, it looks like a pointlike object. These diﬀerent oscillatory states of the string are analogous to the diﬀerent polarization states of the particles. Note that the mass of the string state itself depends on the ...

UNSTRUNG

... Medal, considered the Nobel Prize of mathematics. It was Witten who ushered in the second string-theory revolution, which addressed a conundrum that had arisen, in part, from all those extra dimensions. They had to be curled up so that they were invisibly small, but it turned out that there were var ...

... Medal, considered the Nobel Prize of mathematics. It was Witten who ushered in the second string-theory revolution, which addressed a conundrum that had arisen, in part, from all those extra dimensions. They had to be curled up so that they were invisibly small, but it turned out that there were var ...

The dangers of non-empirical confirmation

... in the real world, but these alternatives are themselves considered credible by their supporters precisely because they themselves have “no alternative” under a different set of assumptions! As a theory of quantum gravity, an alternative to string theory is loop quantum gravity, considered the “only ...

... in the real world, but these alternatives are themselves considered credible by their supporters precisely because they themselves have “no alternative” under a different set of assumptions! As a theory of quantum gravity, an alternative to string theory is loop quantum gravity, considered the “only ...

Untitled - School of Natural Sciences

... not know the guiding underlying principle that explains the form of the equations, and there are innumerable physical quantities that we do not know how to compute from the equations. In recent years string theorists have obtained many interesting and surprising results, giving novel ways of underst ...

... not know the guiding underlying principle that explains the form of the equations, and there are innumerable physical quantities that we do not know how to compute from the equations. In recent years string theorists have obtained many interesting and surprising results, giving novel ways of underst ...

An Inflationary Model In String Theory

... that of the standard model; a positive cosmological constant and inflation. •Challenge is to find vacua that resemble the standard model and make predictions. This might well be possible. ...

... that of the standard model; a positive cosmological constant and inflation. •Challenge is to find vacua that resemble the standard model and make predictions. This might well be possible. ...

String Theory

... • The extra dimensions are hidden a la Kaluza, Klein theory (1921) • Supersymmetry is there but broken (somehow) • The fact that these aren’t observed at current scales is in no sense a theoretical problem, the natural scale for such things would be the string scale ie. around the plank scale. • If ...

... • The extra dimensions are hidden a la Kaluza, Klein theory (1921) • Supersymmetry is there but broken (somehow) • The fact that these aren’t observed at current scales is in no sense a theoretical problem, the natural scale for such things would be the string scale ie. around the plank scale. • If ...

ADVENTURES IN PHYSICS AND MATH Edward Witten From a

... confusion, but it may be that things were clearer even sooner to the senior professors, and their understanding just took a while to filter down to us students. I have gone into so much detail about this to try to explain what my interests were as a graduate student in the mid-1970's. In short, when ...

... confusion, but it may be that things were clearer even sooner to the senior professors, and their understanding just took a while to filter down to us students. I have gone into so much detail about this to try to explain what my interests were as a graduate student in the mid-1970's. In short, when ...

Solving quantum field theories via curved spacetimes

... from three colors to a larger number of colors, N. The gluons that mediate color forces in those theories are analogues of photons, which mediate electromagnetic interactions. In contrast to uncharged photons, however, the gluons are themselves colored, and their number is N 2 − 1. Thus Neff is comp ...

... from three colors to a larger number of colors, N. The gluons that mediate color forces in those theories are analogues of photons, which mediate electromagnetic interactions. In contrast to uncharged photons, however, the gluons are themselves colored, and their number is N 2 − 1. Thus Neff is comp ...

# M-theory

M-theory is a theory in physics that unifies all consistent versions of superstring theory. The existence of such a theory was first conjectured by Edward Witten at a string theory conference at the University of Southern California in the spring of 1995. Witten's announcement initiated a flurry of research activity known as the second superstring revolution.Prior to Witten's announcement, string theorists had identified five versions of superstring theory. Although these theories appeared at first to be very different, work by several physicists showed that the theories were related in intricate and nontrivial ways. In particular, physicists found that apparently distinct theories could be unified by mathematical transformations called S-duality and T-duality. Witten's conjecture was based in part on the existence of these dualities and in part on the relationship of the string theories to a field theory called eleven-dimensional supergravity.Although a complete formulation of M-theory is not known, the theory should describe two- and five-dimensional objects called branes and should be approximated by eleven-dimensional supergravity at low energies. Modern attempts to formulate M-theory are typically based on matrix theory or the AdS/CFT correspondence. According to Witten, M should stand for “magic”, “mystery”, or “membrane” according to taste, and the true meaning of the title should be decided when a more fundamental formulation of the theory is known.Investigations of the mathematical structure of M-theory have spawned important theoretical results in physics and mathematics. More speculatively, M-theory may provide a framework for developing a unified theory of all of the fundamental forces of nature. Attempts to connect M-theory to experiment typically focus on compactifying its extra dimensions to construct candidate models of our four-dimensional world, although so far none have been verified to give rise to physics as observed at, for instance, the Large Hadron Collider.