P. Olesen

University of Copenhagen, Physics, Faculty Member

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Papers by P. Olesen

Infrared equivalence of strongly and weakly coupled gauge theories

Nuclear Physics B, 1976

Correlations in semi-inclusive cross-sections

Il Nuovo Cimento A, 1972

We consider cross-sections for semi-inclusive experiments of the type a ÷ b -+ C(pl) _L ... _~_ e... more

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Comparison of forward dispersion relations with experiments at 8, 10 and 12 GeV

Physics Letters, 1965

ABSTRACT

Integrable version of Burgers equation in magnetohydrodynamics

Physical review. E, Statistical, nonlinear, and soft matter physics, 2003

It is pointed out that for the case of (compressible) magnetohydrodynamics (MHD) with the fields ... more It is pointed out that for the case of (compressible) magnetohydrodynamics (MHD) with the fields v(y)(y,t) and Bx(y,t), one can have equations of the Burgers type which are integrable. We discuss the solutions. It turns out that the propagation of the nonlinear effects is governed by the initial velocity (as in Burgers case) as well as by the initial Alfvén velocity. Many results previously obtained for the Burgers equation can be transferred to the MHD case. We also discuss equipartition v(y)=+/-Bx. It is shown that an initial localized small scale magnetic field will end up in fields moving to the left and the right, thus transporting energy from smaller to larger distances.

Three-dimensional lattice gauge theory and strings

Nuclear Physics B, 1984

ABSTRACT We consider SU(2) lattice gauge theory in three dimensions. The Wilson loops are found t... more

$Research paper thumbnail of TheN/D method and the diffraction picture—II$

TheN/D method and the diffraction picture—II

Recent results in SU (2) gauge theory

A relation between self interaction and mutual interaction

ABSTRACT

$Research paper thumbnail of TheN/D method and the diffraction picture$

TheN/D method and the diffraction picture

Phase transition in Wilson loop correlator from AdS/CFT correspondence

A previous calculation of the phase transition in the Wilson loop correlator in the zero temperat... more A previous calculation of the phase transition in the Wilson loop correlator in the zero temperature AdS/CFT correspondence is extended to the case where the loops are concentric circles of unequal radii. This phase transition occurs due to the instability of the classical string stretched between the loops. We compute the string action and its expansion in the distance h between the loops for small h. We also find that the connected minimal surface is subleading or does not even exist when h = 0 and the radii are considerably different. This feature has no analogue in flat space.

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Strings and QCD

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The partial wave amplitude for high-energy pion-pion scattering

Nuclear Physics, 1964

... 22a), since the integrals obtain the main contribution from values of v&amp;#x27; near v,... more ... 22a), since the integrals obtain the main contribution from values of v&amp;#x27; near v, in which case the factor ALI)(v&amp;#x27;)AI) (v) is almost zero. Using eq. (22) one can write eq. (25) as [Ri(v)]2 = V+1 1 1 v fO v&amp;#x27; N.01)(v&amp;#x27;)Ri(V), . (26 ) v Nl(l)(v) Re A(v) no v&amp;#x27;+1 v&amp;#x27;(v&amp;#x27;v) 648 P. OLESEN It is easily ...

$Research paper thumbnail of The N/D method and the diffraction picture—II$

The N/D method and the diffraction picture—II

Nuovo Cimento Della Societa Italiana Di Fisica A-nuclei Particles and Fields - NUOVO CIMENTO A-NUCL PART F, 1965

A W--dressed Electroweak String

We give plausibility arguments for the existence of a $W$--dressed electroweak string for the \ws... more We give plausibility arguments for the existence of a $W$--dressed electroweak string for the \ws ~model with $\th_W = 0$. This string is a $Z$--string which in the core has a finite energy contribution from $W$--condensation induced by the anomalous magnetic moment in the \ym field. The solution which has minimum energy at $r=0$ interpolates between the unbroken $(r=0)$ and the broken $(r \ra \infty) \ SU(2) \times U_y(1)$ phase.

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On the comparison of forward pion-nucleon dispersion relations with experiments

Nuovo Cimento Della Societa Italiana Di Fisica A-nuclei Particles and Fields - NUOVO CIMENTO A-NUCL PART F, 1966

Summary In a previous paper it was shown that it is possible to construct some tests of forward ... more Summary In a previous paper it was shown that it is possible to construct some tests of forward dispersion relations which are independent of the high-energy behaviour of the total cross-sections. The present paper contains an investigation of the dependence of these tests on the threshold parameters (f 2 and the scattering lengths). It is well known that the threshold parameters are not very well determined experimentally. Therefore, in order that our tests are reliable, it is necessary that they are practically independent of the threshold parameters. It turns out that there exist two tests of the forward dispersion relations which are practically independent of the actual values of the threshold parameters. This result yields the most critical test of forward dispersion relations (i.e. essentially local commutativity, Lorentz invariance and unitarity) proposed up to now. In the spirit of the previous work it is then shown that the two threshold parametersf 2 andT S (m) can be de...

Primordial Magnetic Fields and Their Development

In this talk I discuss the non-linear development of magnetic fields in the early universe. I ver... more In this talk I discuss the non-linear development of magnetic fields in the early universe. I very briefly mention a number of particle physics mechanisms for generating magnetic fields in the early universe, but the emphasis is on a review of the field theoretic aspects of the developments of these fields, mainly on the occurence of inverse cascades, i.e. generation of order from disorder in the sense of transfer of energy from smaller to larger scales. In this connection it is also briefly reviewed how the Silk effect (photon diffusion) is counteracted by the inverse cascade.

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Remarks on the heavy quark potential in the supergravity approach

Journal of High Energy Physics, 1998

We point out certain unexpected features of the planar QCD 3 confining potential, as computed fro... more We point out certain unexpected features of the planar QCD 3 confining potential, as computed from a classical worldsheet action in an AdS metric via the Maldacena conjecture. We show that there is no Lüscher c/R term in the static-quark potential, which is contrary to both the prediction of various effective string models, and the results of some recent lattice Monte Carlo studies. It is also noted that the glueball masses extracted from classical supergravity tend to finite, coupling-independent constants in the strong coupling limit, even as the string tension tends to infinity in the same limit; this is a counter-intuitive result.

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Worldsheet fluctuations and the heavy quark potential in the AdS/CFT approach

Journal of High Energy Physics, 1999

ABSTRACT We consider contributions to the heavy quark potential, in the AdS/CFT approach to SU(N)... more ABSTRACT We consider contributions to the heavy quark potential, in the AdS/CFT approach to SU(N) gauge theory, which arise from first order fluctuations of the associated worldsheet in anti-deSitter space. The gaussian fluctuations occur around a classical worldsheet configuration resembling an infinite square well, with the bottom of the well lying at the AdS horizon. The eigenvalues of the corresponding Laplacian operators can be shown numerically to be very close to those in flat space. We find that two of the transverse world sheet fields become massive, which may have implications for the existence of a L{\&quot;u}scher term in the heavy quark potential. It is also suggested that these massive degrees of freedom may relate to extrinsic curvature in an effective D=4 string theory. Comment: 16 pages, 3 figures, Latex2e. Added some remarks on the incompatibility of the AdS/CFT and the lattice regulators, and on the appropriate boundary conditions

A dual quark prison

Physics Letters B, 1974

ABSTRACT

Infrared stability of the Yang-Mills theory in the zero-instanton sector

Physics Letters B, 1977

Abstracting the decoupling theorem of Appelqmst and Carazzone from perturbation theory we show th... more

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