arXiv subjects
Publications and source records attributed to Ulf H. Danielsson.
In this paper we investigate how various equivalences between effective field theories of $N=2$ SUSY Yang-Mills theory with matter can be understood through Higgs breaking, i.e. by giving expectation values to squarks. We give explicit expressions for the flat directions for a wide class of examples.
We find low energy equivalences between $N=2$ supersymmetric gauge theories with different simple gauge groups with and without matter. We give a construction of equivalences based on subgroups and find all examples with maximal simple subgroups. This is used to solve some theories with exceptional gauge groups $G_2$ and $F_4$. We are also able to solve an $E_6$ theory on a codimension one submanifold of its moduli space.
In this paper we study the polarization tensor of photons in a QED plasma in the presence of a magnetic field. We do it both at vanishing and at finite temperature. We use two different methods to compute the polarization tensor components $Π^{μν}$ within the one-loop approximation. The first starts from the effective Lagrangian of the system and relates $Π^{μν}$ to the thermodynamic quantities. The second makes use of the electron propagator in an external magnetic field. In this second approach we use an imaginary time formalism. These methods give consistent results in the first non-vanishing order in the photon 4-momentum. Beyond this limit the first method is not applicable and the introduction of the second can not be avoided. We give some physical interpretations of our results.
We write down the weak-coupling limit of N=2 supersymmetric Yang-Mills theory with arbitrary gauge group \( G \). We find the weak-coupling monodromies represented in terms of \( Sp(2r,\bzeta ) \) matrices depending on paths closed up to Weyl transformations in the Cartan space of complex dimension r, the rank of the group. There is a one to one relation between Weyl orbits of these paths and elements of a generalized braid group defined from \( G \). We check that these weak-coupling monodromies behave correctly in limits of the moduli space corresponding to restrictions to subgroups. In the case of $SO(2r+1)$ we write down the complex curve representing the solution of the theory. We show that the curve has the correct monodromies.
This is a writeup of a talk given at the Oskar Klein Centenery Symposium, Stockholm, September 19-21, 1994. It is an essay on the black hole information paradox and its connection with thermodynamics and the foundations of quantum mechanics.
In this paper, correlation functions of tachyons in the two-dimensional black-hole are studied. The results are shown to be consistent with the prediction of the deformed matrix model.
In this paper the $c=1$ string theory is studied from the point of view of topological field theories. Calculations are done for arbitrary genus. A change in the prescription is proposed, which reproduces the results of the $1/x^2$ deformed matrix model. It is proposed that the deformed matrix model is related to a D-series Landau-Ginzburg superpotential.
The $1/x^{2}$ deformed $c=1$ matrix model is studied at finite radius and non-zero cosmological constant. Calculational techniques are presented and illustrated in some examples. Furthermore, a new kind of $R \rightarrow 1/R$ duality is discovered which mixes different genus.
In this paper the $c=1$ matrix model deformed by a $1/x^{2}$ piece is discussed. Tachyon correlation functions are calculated up to genus two using methods similar to those for the undeformed case. The possible connection with the two dimensional black hole is also considered. In particular, restrictions on naked singularities imposed by the matrix model are found.
The purpose of this paper is to analyse, in the light of information theory and with the arsenal of (elementary) quantum mechanics (EPR correlations, copying machines, teleportation, mixing produced in sub-systems owing to a trace operation, etc.) the scenarios available on the market to resolve the so-called black-hole information paradox. We shall conclude that the only plausible ones are those where either the unitary evolution of quantum mechanics is given up, in which information leaks continuously in the course of black-hole evaporation through non-local processes, or those in which the world is polluted by an infinite number of meta-stable remnants.
A quantum version of 2D super dilaton gravity containing a black hole is constructed for $N>8$. A previous disagreement as to whether this is possible or not is resolved.
In this work the quantum theory of two dimensional dilaton black holes is studied using the Wheeler De Witt equation. The solutions correspond to wave functions of the black hole. It is found that for an observer inside the horizon, there are uncertainty relations for the black hole mass and a parameter in the metric determining the Hawking flux. Only for a particular value of this parameter, can both be known with arbitrary accuracy. In the generic case there is instead a relation which is very similar to the so called string uncertainty relation.
This thesis is a study of two dimensional noncritical string theory. The main tool which is used, is the matrix model. Introductions to both the Liouville model and its matrix model formulation are included. In particular the special states are discussed. Some calculations of partition functions on genus one using field theory techniques are given. Nonperturbative issues and string theory at finite radius are discussed. Zero momentum correlation functions are calculated using the matrix model. One important result is a set of recursion relations. The treatment is extended to nonzero momentum. The main result is a clear identification of the special states. Some comments on the Wheeler de Witt equation is given. The matrix model $W_{\infty}$ algebra is introduced. This organizes the previous results. In particular, a simple derivation of the genus zero tachyon correlation functions is given. The results are then extended to higher genus. It is seen how a deformation of the algebra is responsible for much of the higher genus structure. Some very explicit formulae are derived. Then the Liouville and matrix model calculations are compared followed by some general conclusions.
We use the W-infinity symmetry of c=1 quantum gravity to compute matrix model special state correlation functions. The results are compared, and found to agree, with expectations from the Liouville model.