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String theory has the peculiar property that quantum formulas were discovered before any classical formulas and that the quantum formulas are unusually beautiful. It has always been perplexingly hard to find an underlying classical theory via whose quantization string theory could be effectively understood. Nowadays, in the light of quantum duality symmetries and the unification of the different string theories in M theory, we are beginning to suspect a relation between quantum and classical physics quite different from what we have had before. The matrix model may be pointing the way, but we have not yet grasped its implications.
No abstract is provided for this article.
Three subjects are considered here: a self-dual non-critical string that appears in Type IIB superstring theory at points in ${\rm K3}$ moduli space where the Type IIA theory has extended gauge symmetry; a conformal field theory singularity at such points which may signal quantum effects that persist even at weak coupling; and the rich dynamics of the real world under compactification, which may be relevant to some attempts to explain the vanishing of the cosmological constant.
The temperature and field dependence of the magnetic susceptibility of [PhenH2] [MnCl5] have been determined over the range 300 K to 1.43 K. The complex behaves as a simple Curie paramagnet over this temperature interval with no evidence of either significant intermolecular exchange, single ion zero field splitting or spin-orbit effects in the magnetic behavior. These results are considered in terms of the known electronic and molecular structure of the complex.
U(1) gauge theory on ${\bf R}^4$ is known to possess an electric-magnetic duality symmetry that inverts the coupling constant and extends to an action of $SL(2,{\bf Z})$. In this paper, the duality is studied on a general four-manifold and it is shown that the partition function is not a modular-invariant function but transforms as a modular form. This result plays an essential role in determining a new low-energy interaction that arises when N=2 supersymmetric Yang-Mills theory is formulated on a four-manifold; the determination of this interaction gives a new test of the solution of the model and would enter in computations of the Donaldson invariants of four-manifolds with $b_2^+\leq 1$. Certain other aspects of abelian duality, relevant to matters such as the dependence of Donaldson invariants on the second Stieffel-Whitney class, are also analyzed.
No abstract is provided for this article.
We determine the general coupling of an arbitrary number of massless pin (0, 1 2 ) multiplets to N = 2 supergravity. We find that the matter coupling has a natural description in the language of the supersymmetric non-linear sigma model, where the sigma model is based on a quaternionic manifold. This implies that the matter self-couplings that are allowed in global N = 2 supersymmetry are forbidden in supergravity, and vice versa.
No abstract is provided for this article.
No abstract is provided for this article.
No abstract is provided for this article.
Share Icon Share Twitter Facebook Reddit LinkedIn Reprints and Permissions Cite Icon Cite Search Site Citation Guy Faucher, Edward Witten; Quark history. Physics Today 1 March 1981; 34 (3): 80–81. https://doi.org/10.1063/1.2914488 Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentPhysics Today Search Advanced Search
It has been argued based on electric-magnetic duality and other ingredients that the Jones polynomial of a knot in three dimensions can be computed by counting the solutions of certain gauge theory equations in four dimensions. Here, we attempt to verify this directly by analyzing the equations and counting their solutions, without reference to any quantum dualities. After suitably perturbing the equations to make their behavior more generic, we are able to get a fairly clear understanding of how the Jones polynomial emerges. The main ingredient in the argument is a link between the four-dimensional gauge theory equations in question and conformal blocks for degenerate representations of the Virasoro algebra in two dimensions. Along the way we get a better understanding of how our subject is related to a variety of new and old topics in mathematical physics, ranging from the Bethe ansatz for the Gaudin spin chain to the $M$-theory description of BPS monopoles and the relation between Chern-Simons gauge theory and Virasoro conformal blocks.
We propose that the ten-dimensional E 8 × E 8 heterotic string is related to an eleven-dimensional theory on the orbifold R 10 × S1/Z 2 in the same way that the Type IIA string in ten dimensions is related to R 10 × S1 . This in particular determines the strong coupling behavior of the ten-dimensional E 8 × E 8 theory. It also leads to a plausible scenario whereby duality between SO(32) heterotic and Type I superstrings follows from the classical symmetries of the eleven-dimensional world, just as the SL(2, Z) duality of the ten-dimensional Type IIB theory follows from eleven-dimensional diffeomorphism invariance.
No abstract is provided for this article.
We re-examine the black hole solutions in classical theories of dilaton gravity in two dimensions. We consider an arbitrary dilaton potential such that there are black hole solutions asymptotic at infinity to the nearly $\mathrm{AdS}_2$ solutions of JT gravity, and such that the black hole energy and entropy are bounded below. We show that if there is a black hole solution with negative specific heat at some temperature $T$, then at the same temperature there is a black hole solution with lower free energy and positive specific heat. As the temperature is increased from 0 to infinity, the black hole energy and entropy increase monotonically but not necessarily continuously; there can be first order phase transitions, similar to the Hawking-Page transition. These theories can also have solutions corresponding to closed universes.
An attempt is made to resolve certain discrepancies between instatons, the quark model and the 1/N expansion. It is argued that the most attractive resolution of these discrepancies is the possibility that quantum corrections cause the instanton gas to disappear in QCD. A two-dimensional model is described in which it can be seen explicitly that such a disappearance takes place. (This model has been investigated independently by D'Adda, Di Vecchia, and Lüscher.)
There are hints of a novel object (Planet 9) with a mass $5-10$ $M_\oplus$ in the outer Solar System, at a distance of order 500 AU. If it is a relatively conventional planet, it can be found in telescopic searches. Alternatively, it has been suggested that this body might be a primordial black hole (PBH). In that case, conventional searches will fail. A possible alternative is to probe the gravitational field of this object using small, laser-launched spacecraft, like the ones envisioned in the Breakthrough Starshot project. With a velocity of order $.001~c$, such spacecraft can reach Planet 9 roughly a decade after launch and can discover it if they can report timing measurements accurate to $10^{-5}$ seconds back to Earth.
