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  • 101.
    Berggren, Karl-Fredrik
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska högskolan.
    Hur står det till med SFS?2011Ingår i: Fysikaktuellt, ISSN 0283-9148, nr 4, s. 5-5Artikel i tidskrift (Övrig (populärvetenskap, debatt, mm))
  • 102.
    Berggren, Karl-Fredrik
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik.
    International evaluation of the Swedish polar research organization2008Rapport (Övrigt vetenskapligt)
    Abstract [en]

      

  • 103.
    Berggren, Karl-Fredrik
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska högskolan.
    Jakten på liv i universum2013Ingår i: Fysikaktuellt, ISSN 0283-9148, nr 4, s. 26-26Artikel, recension (Övrig (populärvetenskap, debatt, mm))
  • 104.
    Berggren, Karl-Fredrik
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska högskolan.
    NSC during 20 years2009Konferensbidrag (Övrigt vetenskapligt)
  • 105.
    Berggren, Karl-Fredrik
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska högskolan.
    Parallella världar - Fysikaktuellt nr 22012Övrigt (Övrig (populärvetenskap, debatt, mm))
  • 106.
    Berggren, Karl-Fredrik
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik.
    Promoveringsskrift våren 20072007Övrigt (Övrig (populärvetenskap, debatt, mm))
  • 107.
    Berggren, Karl-Fredrik
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska högskolan.
    Signerat: Nya krafter vid rodret2012Ingår i: Fysikaktuellt, ISSN 0283-9148, nr 4, s. 3-3Artikel i tidskrift (Övrig (populärvetenskap, debatt, mm))
  • 108.
    Berggren, Karl-Fredrik
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska högskolan.
    Signerat; Välkommen till år 20102010Ingår i: Fysikaktuellt, ISSN 0283-9148, nr 1, s. 3-3Artikel i tidskrift (Övrig (populärvetenskap, debatt, mm))
  • 109.
    Berggren, Karl-Fredrik
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska högskolan.
    Slow physics2012Ingår i: Fysikaktuellt, ISSN 0283-9148, nr 3, s. 3-3Artikel i tidskrift (Övrig (populärvetenskap, debatt, mm))
  • 110.
    Berggren, Karl-Fredrik
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska högskolan.
    Spännande program på Nordiska Fysikdagarna2011Ingår i: Fysikaktuellt, ISSN 0283-9148, nr 2, s. 21-21Artikel i tidskrift (Övrig (populärvetenskap, debatt, mm))
  • 111.
    Berggren, Karl-Fredrik
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik.
    The story of Cray number nine2008Övrigt (Övrig (populärvetenskap, debatt, mm))
    Abstract [en]

      

  • 112.
    Berggren, Karl-Fredrik
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska högskolan.
    Åsikter om infrastruktursatsningarna2012Ingår i: Fysikaktuellt, ISSN 0283-9148, nr 3, s. 5-5Artikel i tidskrift (Övrig (populärvetenskap, debatt, mm))
  • 113.
    Berggren, Karl-Fredrik
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska högskolan.
    Maksimov, Dmitrii N.
    L.V. Kirensky Institute of Physics.
    Sadreev, Almas F.
    Linköpings universitet, Institutionen för fysik, kemi och biologi. Linköpings universitet, Tekniska högskolan.
    Höhmann, Ruven
    AG Quantenchaos.
    Kuhl, Ulrich
    AG Quantenchaos.
    Stöckmann, Hans-Jürgen
    AG Quantenchaos.
    Quantum stress in chaotic billiards2008Ingår i: Physical Review E. Statistical, Nonlinear, and Soft Matter Physics: Statistical Physics, Plasmas, Fluids, and Related Interdisciplinary Topics, ISSN 1063-651X, E-ISSN 1095-3787, Vol. 77, nr 066209Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    This paper reports on a joint theoretical and experimental study of the Pauli quantum-mechanical stress tensor T(x,y) for open two-dimensional chaotic billiards. In the case of a finite current flow through the system the interior wave function is expressed as =u+iv. With the assumption that u and v are Gaussian random fields we derive analytic expressions for the statistical distributions for the quantum stress tensor components T. The Gaussian random field model is tested for a Sinai billiard with two opposite leads by analyzing the scattering wave functions obtained numerically from the corresponding Schrödinger equation. Two-dimensional quantum billiards may be emulated from planar microwave analogs. Hence we report on microwave measurements for an open two-dimensional cavity and how the quantum stress tensor analog is extracted from the recorded electric field. The agreement with the theoretical predictions for the distributions for T(x,y) is quite satisfactory for small net currents. However, a distinct difference between experiments and theory is observed at higher net flow, which could be explained using a Gaussian random field, where the net current was taken into account by an additional plane wave with a preferential direction and amplitude.

  • 114.
    Berggren, Karl-Fredrik
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik.
    Albrow, Michael
    Fermi National Lab.
    Grenier, Isabelle
    CEA U Paris VII.
    Bedell, Kevin
    Boston College.
    Schwalm, Dirk
    Max Planck Institute for Nuclear Physics.
    Focusing on Quality; Panel 3: Physics, Theoretical Physics2008Rapport (Övrigt vetenskapligt)
    Abstract [en]

      

  • 115.
    Berggren, Karl-Fredrik
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik.
    Carlile, Colin
    Carlsson, Patrik
    Lunds universitet.
    Sverige rustar för neutronkamp2007Ingår i: Fysikaktuellt, ISSN 0283-9148, nr 3, s. 14-15Artikel i tidskrift (Övrig (populärvetenskap, debatt, mm))
    Abstract [sv]

       

  • 116.
    Berggren, Karl-Fredrik
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska högskolan.
    Cederwall, Martin
    Chalmers.
    Forssell-Aronsson, Eva
    Sahlgrenska akademin.
    Fredriksson, Billy
    Vetenskapsrådets ämnesråd för naturvetenskap och teknik.
    Goksör, Mattias
    Göteborgs universtitet.
    Häggström, Olle
    Chalmers.
    Lundström, Ingemar
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad Fysik. Linköpings universitet, Tekniska högskolan.
    Mårtensson, Ann-Sofie
    Högskolan i Borås.
    Sandelius, Anna Stina
    Göteborgs universitet.
    Wennberg, Ann-Marie
    Sahlgrenska universitetssjukhuset.
    Stärk matematiken och naturvetenskapen i nya gymnasiet2010Ingår i: NyTeknikArtikel i tidskrift (Övrig (populärvetenskap, debatt, mm))
  • 117.
    Berggren, Karl-Fredrik
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska högskolan.
    Fors, Cecilia
    Fysikersamfundet 90 år2010Ingår i: Fysikaktuellt, ISSN 0283-9148, nr 2, s. 12-12Artikel i tidskrift (Övrig (populärvetenskap, debatt, mm))
  • 118.
    Berggren, Karl-Fredrik
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska högskolan.
    Gunnarsson, Svante
    Linköpings universitet, Institutionen för systemteknik, Reglerteknik. Linköpings universitet, Tekniska högskolan.
    Svensson, Tomas
    Linköpings universitet, Institutionen för systemteknik. Linköpings universitet, Tekniska högskolan.
    Wiklund, Ingela
    Linköpings universitet, Tekniska högskolan.
    The Development of the Applied Physics and Electrical Engineering (Y) Programme at Linköping University through Participation in the CDIO Initiative2005Ingår i: Proceedings of the 8th UICEE Annual Conference on Engineering Education, 2005, s. 321-324Konferensbidrag (Refereegranskat)
  • 119.
    Berggren, Karl-Fredrik
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska högskolan.
    Hallonsten, Olof
    Göteborgs universitet.
    Timeline of major events2012Ingår i: In pursuit of a promise: Perspectives on the political process to establish the European Spallation Source (ESS) in Lund, Sweden / [ed] Olof Hallonsten, Arkiv förlag & tidskrift, 2012, s. 21-30Kapitel i bok, del av antologi (Övrigt vetenskapligt)
    Abstract [en]

    On 28 May 2009, at a closed meeting in Brussels, ministers and state secretaries of education and science from several EU countries decided to build the European Spallation Source (ESS) in Lund, Sweden. Or did they?It is common for big European science projects to be surrounded by secrecy and political deceit, but the ESS is extraordinary in its elusiveness. There is a remarkable lack of concrete economic, political, technical and scientific underpinnings to the project  but a boasting certainty in the promises of future paybacks.The ESS is an accelerator-based neutron spallation facility that will cost billions of Euros to build and run. It is expected to bring new knowledge in several fields including materials science, energy research, and the life sciences. But its financing is not yet certain, and future returns hard to predict. How then could the decision to build ESS occur? Why was there so little organized resistance?This book places the ESS project in its political and scientific context. It links the decisions taken to the history of Big Science in Europe and in Sweden. It looks at the dynamic political processes of establishing this megaproject in a small town in the south of Sweden. The eight chapters start from a paradoxical state of affairs: The ESS is not funded, and not formally decided in any binding agreements  yet it is treated as a future reality, locally and nationally, loaded with promises of scientific, economic and social returns.The book makes a much-needed first contribution to the analysis of the ESS project and its political, environmental, and social ramifications. It should be read by scholars of science and technology studies, politicians and the interested general public.

  • 120.
    Berggren, Karl-Fredrik
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska högskolan.
    Irina I., Yakimenko
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska högskolan.
    Basic Modeling of Openness, Quantum States and Transport in Two- and Three-Dimensional Ballistic Cavities2010Ingår i: Journal of Siberian Federal University. Mathematics & Physics, Vol. 3, s. 280-288Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A basic model for particle states and current flow in open quantum dots/billiards are investigated. The model is unconventional and extends the use of complex potentials first introduced in phenomenological nuclear inelastic scattering theory (the optical model). Attached leads/source drain are represented by complex potentials. Probability densities and currents flows for open 2D quantum dots/billiards are calculated and the results are compared with microwave measurements used to emulate the dot. We also apply the model to a recangular enclosure and report on helical flows guided by nodal lines and disc-like accumulations of flow lines. The model is of conceptual as well as practical and educational interest.

  • 121.
    Berggren, Karl-Fredrik
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik.
    Jaksch, Peter
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik.
    Yakymenko, Iryna
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik.
    Effects of electron interactions at crossings of Zeeman-split subbands in quantum wires2005Ingår i: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 71, nr 11, s. 115303-1-115303-5, artikel-id 115303Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Recent experimental studies of Zeeman-split one-dimensional subbands in ballistic quantum wires in an in-plane magnetic field show that additional nonquantized conductance structures occur as subbands cross at low electron densities [A. C. Graham et al., Phys. Rev.Lett. 91, 136404 (2003)]. These structures are called 0.7 analogs. We analyze the experimental transconductance data within the Kohn-Sham spin-density-functional method, including exchange and correlation effects for an infinite split-gate quantum wire in a parallel, in-plane magnetic field B∥. Energy levels are found to rearrange abruptly as they cross due to polarization effects driven by exchange and Coulomb interactions. Experimental qualitative features are explained well by this model. ©2005 The American Physical Society.

  • 122.
    Berggren, Karl-Fredrik
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik.
    Larsson, Johan
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi.
    Bengtsson, Olof
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi.
    Electrical Resonance Circuits as Analogs to Quantum Mechanical Billiards2006Ingår i: Acta Physica Polonica. A, ISSN 0587-4246, E-ISSN 1898-794X, Vol. 109, s. 33-42Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We propose that a two-dimensional electric network may be used for fundamental studies of wave function properties, transport, and related statistics. Using Kirchhoff 's current law and the jw-method we find that the network is analogous to a discretized Schrodinger equation for quantum billiards and clots. Thus the complex electric potentials play the role of quantum rnechanical wave functions.

  • 123.
    Berggren, Karl-Fredrik
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska högskolan.
    Ljung, P.
    Siemens Corporate Research.
    Nature of streamlines for Berry-type wave functions in open 3D cavities2009Ingår i: MATHEMATICAL MODELING OF WAVE PHENOMENA, American Institute of Physics (AIP), 2009, Vol. 1106, s. 253-259Konferensbidrag (Refereegranskat)
    Abstract [en]

    We explore preliminary a 3D wave cavity in which the interior complex wave functions are of Berry-type. Streamlines and novel disc-like features are uncovered by means of selective and interactive visualization.

  • 124.
    Berggren, Karl-Fredrik
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik.
    Ljung, Patric
    Siemens Corporate Research, USA.
    Nature of Streamlines for Berry-type Wave Functions in Open 3D Cavities2008Ingår i: Radio Science and Communications Mathematical Modelling of Wave Phenomena,2008, 2008, s. 41-42Konferensbidrag (Refereegranskat)
    Abstract [en]

      

  • 125.
    Berggren, Karl-Fredrik
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska högskolan.
    Malm, M
    Wärnsby, M
    Sjöberg, M
    ESS - European Spallation Source – tillstånd för miljö och utveckling2009Konferensbidrag (Övrigt vetenskapligt)
  • 126.
    Berggren, Karl-Fredrik
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska högskolan.
    Matic, Aleksandar
    Chalmers tekniska högskola, Göteborg.
    Science at the ESS: a brief outline2012Ingår i: In Pursuit of a Promise: Perspectives on the political process to establish the European Spallation Source (ESS) in Lund, Sweden / [ed] Olof Hallonsten, Arkiv förlag & tidskrift, 2012, s. 31-47Kapitel i bok, del av antologi (Övrigt vetenskapligt)
    Abstract [en]

    On 28 May 2009, at a closed meeting in Brussels, ministers and state secretaries of education and science from several EU countries decided to build the European Spallation Source (ESS) in Lund, Sweden. Or did they?It is common for big European science projects to be surrounded by secrecy and political deceit, but the ESS is extraordinary in its elusiveness. There is a remarkable lack of concrete economic, political, technical and scientific underpinnings to the project  but a boasting certainty in the promises of future paybacks.The ESS is an accelerator-based neutron spallation facility that will cost billions of Euros to build and run. It is expected to bring new knowledge in several fields including materials science, energy research, and the life sciences. But its financing is not yet certain, and future returns hard to predict. How then could the decision to build ESS occur? Why was there so little organized resistance?This book places the ESS project in its political and scientific context. It links the decisions taken to the history of Big Science in Europe and in Sweden. It looks at the dynamic political processes of establishing this megaproject in a small town in the south of Sweden. The eight chapters start from a paradoxical state of affairs: The ESS is not funded, and not formally decided in any binding agreements  yet it is treated as a future reality, locally and nationally, loaded with promises of scientific, economic and social returns.The book makes a much-needed first contribution to the analysis of the ESS project and its political, environmental, and social ramifications. It should be read by scholars of science and technology studies, politicians and the interested general public.

  • 127.
    Berggren, Karl-Fredrik
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik.
    Ouchterlony, T
    Linkoping Univ, Dept Phys & Measurement Technol, S-58183 Linkoping, Sweden.
    Chaos in a quantum dot with spin-orbit coupling2001Ingår i: Foundations of physics, ISSN 0015-9018, E-ISSN 1572-9516, Vol. 31, nr 2, s. 233-242Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Level statistics are nodal point distribution in a rectangular semiconductor quantum dot are studies for different degrees of spin-orbit coupling. The chaotic features occurring from the spin-orbit coupling have no classical counterpart. Using experimental values of GaSb/InAs/GaSb semiconductor quantum wells we find that level repulsion can lead to the semi-Poisson distribution for nearest level separations. Nodal lines and nodal points are also investigated. Comparison is made with nodal point distributions for fully chaotic states.

  • 128.
    Berggren, Karl-Fredrik
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik.
    Pepper, M
    Linkoping Univ, Dept Phys & Measurement Technol, S-58183 Linkoping, Sweden Cavendish Lab, Semicond Phys Grp, Cambridge CB3 0HE, England Toshiba Res Europe, Cambridge Res Lab, Cambridge CB4 0WE, England TeraView Ltd, Cambridge CB4 0WE, England.
    New directions with fewer dimensions2002Ingår i: Physics world, ISSN 0953-8585, Vol. 15, nr 10, s. 37-42Artikel i tidskrift (Refereegranskat)
  • 129.
    Berggren, Karl-Fredrik
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska högskolan.
    Pepper, Michael
    University College London.
    Electrons in one dimension2010Ingår i: Philosophical Transactions. Series A: Mathematical, physical, and engineering science, ISSN 1364-503X, E-ISSN 1471-2962, Vol. 368, s. 1141-1162Artikel, forskningsöversikt (Refereegranskat)
    Abstract [en]

    In this article, we present a summary of the current status of the study of the transport of electrons confined to one dimension in very low disorder GaAs–AlGaAs heterostructures. By means of suitably located gates and application of a voltage to ‘electrostatically squeeze’ the electronic wave functions, it is possible to produce a controllable size quantization and a transition from two-dimensional transport. If the length of the electron channel is sufficiently short, then transport is ballistic and the quantized subbands each have a conductance equal to the fundamental quantum value 2e2/h, where the factor of 2 arises from the spin degeneracy. This mode of conduction is discussed, and it is shown that a number of many-body effects can be observed. These effects are discussed as in the spin-incoherent regime, which is entered when the separation of the electrons is increased and the exchange energy is less than kT. Finally, results are presented in the regime where the confinement potential is decreased and the electron configuration relaxes to minimize the electron–electron repulsion to move towards a two-dimensional array. It is shown that the ground state is no longer a line determined by the size quantization alone, but becomes two distinct rows arising from minimization of the electrostatic energy and is the precursor of a two-dimensional Wigner lattice.

  • 130.
    Berggren, Karl-Fredrik
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska högskolan.
    Persson, Bengt
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Bioinformatik. Linköpings universitet, Tekniska högskolan.
    20 years in HPC 1989-20092009Övrigt (Övrig (populärvetenskap, debatt, mm))
  • 131.
    Berggren, Karl-Fredrik
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik.
    Petersen, H.K.
    Thiede, J.
    Rapport - International evaluation of the Swedish organization of polar research (Swedish Research Council)2007Övrigt (Övrig (populärvetenskap, debatt, mm))
    Abstract [en]

        

  • 132.
    Berggren, Karl-Fredrik
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik.
    Sadreev, A.F.
    Kirensky Institute of Physics, 660036, Krasnoyarsk, Russian Federation.
    Starikov, Anton
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi.
    Quantum chaos among nodal points and streamlines at ballistic electron transport through open quantum dots2001Ingår i: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 12, nr 4, s. 562-565Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    We trace signatures of quantum chaos in the distribution of nodal points and streamlines for coherent electron transport through different types of quantum dots (chaotic and regular). We have calculated normalized distribution functions for the nearest distances between nodal points and found that this distribution may be used as a signature of quantum chaos for electron transport in open systems. Different chaotic billiards show the same characteristic distribution function for nodal points. This signature of quantum chaos is well reproduced using well known approaches for chaotic wavefunctions. We have also investigated the quantum flows which display some remarkable features.

  • 133.
    Berggren, Karl-Fredrik
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik.
    Sadreev, Almas
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi.
    Starikov, Anton
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi.
    Crossover from regular to irregular behavior in current flow through open billiards2002Ingår i: Physical Review E - Statistical, Nonlinear, and Soft Matter Physics, ISSN 1539-3755, Vol. 66, nr 1Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We discuss signatures of quantum chaos in terms of distributions of nodal points, saddle points, and streamlines for coherent electron transport through two-dimensional billiards, which are either nominally integrable or chaotic. As typical examples of the two cases we select rectangular and Sinai billiards. We have numerically evaluted distribution functions for nearest distances between nodal points and found that there is a generic form for open chaotic billiards through which a net current is passed. We have also evaluated the distribution functions for nodal points with specific vorticity (winding number) as well as for saddle points. The distributions may be used as signatures of quantum chaos in open systems. All distributions are well reproduced using random complex linear combinations of nearly monochromatic states in nominally closed billiards. In the case of rectangular billiards with simple sharp-cornered leads the distributions have characteristic features related to order among the nodal points. A flaring or rounding of the contact regions may, however, induce a crossover to nodal point distributions and current flow typical for quantum chaos. For an irregular arrangement of nodal points, as for example in the Sinai billiard, the quantum flow lines become very complex and volatile, recalling chaos among classical trajectories. Similarities with percolation are pointed out. ©2002 The American Physical Society.

  • 134.
    Berggren, Karl-Fredrik
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska fakulteten.
    Tellander, Felix
    Lund Univ, Sweden.
    Yakymenko, Iryna
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska fakulteten.
    Basic modelling of transport in 2D wave-mechanical nanodots and billiards with balanced gain and loss mediated by complex potentials2018Ingår i: Journal of Physics: Condensed Matter, ISSN 0953-8984, E-ISSN 1361-648X, Vol. 30, nr 20, artikel-id 204003Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Non-Hermitian quantum mechanics with parity-time (PT) symmetry is presently gaining great interest, especially within the fields of photonics and optics. Here, we give a brief overview of low-dimensional semiconductor nanodevices using the example of a quantum dot with input and output leads, which are mimicked by imaginary potentials for gain and loss, and how wave functions, particle flow, coalescence of levels and associated breaking of PT symmetry may be analysed within such a framework. Special attention is given to the presence of exceptional points and symmetry breaking. Related features for musical string instruments and wolf-notes are outlined briefly with suggestions for further experiments.

  • 135.
    Berggren, Karl-Fredrik
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik.
    Yakimenko, II
    Effects of exchange and electron correlation on conductance and nanomagnetism in ballistic semiconductor quantum point contacts2002Ingår i: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 66, nr 8Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The spontaneous magnetization of a quantum point contact (QPC) formed between two large quantum dots by a lateral confinement of a high-mobility two-dimensional electron gas is studied for a realistic GaAs/AlxGa1-xAs heterostructure. The model of the device incorporates the contributions from a patterned gate, doping, surface states, and mirror charges. To explore the magnetic properties, the Kohn-Sham local spin-density formalism is used with exchange and correlation potentials that allows for local spin polarization. Exchange is the dominant mechanism behind local magnetization within the QPC, while the correlation part is less prominent. However, the correlation potential gives rise to an important correction in the QPC potential. Below the first conduction plateau we thus find a magnetized regime corresponding approximately to a single electron spin. Using an approximate separable saddle potential we compute the conductance and recover the so-called similar to0.7 (2e(2)/h) conduction anomaly plus an additional anomaly at similar to0.4 (2e(2)/h) below which the magnetization collapses.

  • 136.
    Berggren, Karl-Fredrik
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik.
    Yakimenko, I.I.
    Bychkov, A.M.
    Centre for Quantum Computation, Clarendon Laboratory, Oxford OX1 3PU, United Kingdom, Moscow State Engineering Physics Institute, Technical University, 115409 Moscow, Russian Federation.
    On the role of electron exchange and correlation in semiconductor quantum dots2001Ingår i: Nanotechnology, ISSN 0957-4484, E-ISSN 1361-6528, Vol. 12, nr 4, s. 529-532Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    Spontaneous magnetization of single and coupled quantum dots formed by lateral confinement of a high-mobility two-dimensional electron gas is studied for a realistic GaAs/AlGaAs heterostructure. The modelling of the device takes into account contributions from a patterned gate, doping, surface states, and mirror charges. To explore the magnetic properties we use the Kohn-Sham local spin-density formalism including the contributions from electron correlation and exchange. We show by explicit calculations that the exchange is the dominant mechanism driving a spontaneous magnetization of a dot. The correlation potential reduces the amount of level splitting and usually affects the electron content in the dot at a given gate voltage. These effects are, however, small and may be neglected under present circumstances. Single dots with up to 50 electrons have been studied.

  • 137.
    Berggren, Karl-Fredrik
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska högskolan.
    Yakimenko, Irina
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska högskolan.
    Basic Modeling of Openess, Quantum States and Transport in Two- and Three-Dimensional Ballistic Cavities2009Ingår i: Basic Modeling of Openess, Quantum States and Transport in Two- and Three-Dimensional Ballistic Cavities, 2009Konferensbidrag (Refereegranskat)
  • 138.
    Berggren, Karl-Fredrik
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska högskolan.
    Yakimenko, Irina
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska högskolan.
    Hakanen, Jani
    Ericsson AB.
    Modeling of open quantum dots and wave billiards using imaginary potentials for the source and the sink2010Ingår i: New Journal of Physics, ISSN 1367-2630, E-ISSN 1367-2630, Vol. 12, nr 073005Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A heuristic model for particle states and current flow in open ballistictwo-dimensional (2D) quantum dots/wave billiards is proposed. The modelmakes use of complex potentials first introduced in phenomenological nuclearinelastic scattering theory (the optical model). Here we assume that externalinput and output leads connecting the system to the source and the drain regionsmay be represented by complex potentials. In this way, a current may be set upbetween the two ‘pseudo-leads’. Probability densities and current flows for anopen quantum dot are analyzed here numerically and the results are comparedwith the microwave measurements used to emulate the system. The model isof conceptual as well as practical interest. In addition to quantum billiards, itmay be used as a tool per se to analyze transport in classical wave analogues,such as microwave resonators, acoustic resonators, effects of leakage on suchsystems, etc.

  • 139.
    Berggren, Karl-Fredrik
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska högskolan.
    Yakymenko, Irina I.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska högskolan.
    “Correlation and disorder effects on electron transport in modulation-doped semiconductor quantum point contacts” (invited)2013Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    ABSTRACT We simulate effects of electron localization and quantum correlations in realistic GaAs/AlGaAs quantum point contacts (QPCs) in the presence of randomly distributed donors (1) using spin-relaxed density functional theory (DFT/LSDA). Two different configurations of gates defining the QPCs were studied: a split gate and a top gate in addition to the split gate. In both cases we recover the conventional fluctuation-free parabolic electrostatic potential when the distance between the donor layer and the 2D electron gas exceeds 70 nm.  Hence we also find ballistic phenomena such as integer conductance steps as well as the 0.7 anomaly. The electrostatic potential changes dramatically,however, when the random donors are placed closer to the 2D gas. Electron localization is then increased and conductance fluctuations and resonance peaks appear. At the same time the usual conductance steps vanish. By charging asymmetrically the split gates voltage we have found that conductance fluctuations caused by random donors are shifted while the anomalies caused by interaction effects may remain.  Resonance peaks in the conductance derive from localized states inside within the QPC. The nature of electron localization has been discussed in our previous study (2) where we stress the crucial role of confinement potential on the formation of electron localization. In the present study we have shown that electron localization may be caused by randomly distributed donors and play an important role in electron transport, especially near the pinch-off regime. The results of our numerical simulations agree with recent experimental studies (3). 

     

    (1) J.A. Nixon, J.H. Davies, and H.U Baranger, Phys. Rev. B 43, 12638 (1991) 

    (2) I. I. Yakimenko, V. S. Tsykunov and K.-F. Berggren, J. Phys. Condens. Matter 25, 072201 (2013)

    (3) L.W. Smith, K. J. Thomas, M. Pepper, D. A. Ritchie, I. Farrer, J.P. Griffiths, G.A.C. Jones,  J. of Phys.: Conf. Series  376, 012018,  (2012)

  • 140.
    Berggren, Karl-Fredrik
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik.
    Yakymenko, Iryna
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik.
    Electron transport and Nanomagnetism2008Ingår i: Nordforsk Network in Nanospintronics Theory and Simulations,2008, 2008Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

     Electron states, local magnetization and conductance in realistic quantum point contacts (QPCs) with different geometry and applied gate voltages will be discussed for a model GaAs/AlGaAs device. Using the local spin density approximation (LSDA) we recover ferromagnetic spatially split solutions in the pinch-off regime as well as antisymmetric solutions that occur with increasing voltage. These kind of spin states, which may appear in a repeated fashion in the few electron regime, are precursors to an extended ferromagnetic state that may be associated with the 0.7 (2e2/h) conductance anomaly. As the length of the QPC increases, so does the spin polarization and the difference in conductance between up-spin and down-spin electrons, resulting in movement of 0.7 anomaly towards the value of 0.5 (2e2/h). Due to the strong ferromagnetic spin polarization in a long QPC it will effectively work as a spin filter which may be useful for spintronics application. 

  • 141.
    Berggren, Karl-Fredrik
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik.
    Yakymenko, Iryna
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik.
    Nature of electron states and symmetry breaking in quantum point contacts according to the local spin density approximation2008Ingår i: Journal of Physics: Condensed Matter, ISSN 0953-8984, E-ISSN 1361-648X, Vol. 20, nr 16Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Electron states and local magnetization in quantum point contacts (QPCs) with different geometries and applied gate voltages are examined for a model GaAs/AlGaAs device. Using the local spin density approximation (LSDA) we recover ferromagnetic spatially split solutions in the pinch-off regime as well as antisymmetric solutions that occur with decreasing gate voltage. These kinds of spin states, which may appear in a repeated fashion in the few-electron regime, are precursors to an extended ferromagnetic state that may be associated with the 0.7 conductance anomaly. We briefly comment on some recent experiments indicating the presence of bound states (Yoon et al 2007 Phys. Rev. Lett. 99 136805). We have not found any indication of such states but suggest that the accumulations of spin and charge at the two ends of a QPC and associated singlet and triplet states are relevant in this context. © 2008 IOP Publishing Ltd.

  • 142.
    Berggren, Karl-Fredrik
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik.
    Yakymenko, Iryna
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik.
    Quantum cellular automata - Theory, experimentation and prospects2006Ingår i: Quantum Cellular Automata: theory, experimentation and prospects / [ed] Macucci, Massimo, London: Imperial College Press , 2006, s. -300Kapitel i bok, del av antologi (Övrigt vetenskapligt)
    Abstract [en]

    The Quantum Cellular Automaton (QCA) concept represents an attempt to break away from the traditional three-terminal device paradigm that has dominated digital computation. Since its early formulation in 1993 at Notre Dame University, the QCA idea has received significant attention and several physical implementations have been proposed. This book provides a comprehensive discussion of the simulation approaches and the experimental work that have been undertaken on the fabrication of devices capable of demonstrating the fundamentals of QCA action. Complementary views of future perspectives for QCA technology are presented, highlighting a process of realistic simulation and of targeted experiments that can be assumed as a model for the evaluation of future device proposals.Show more Show less

  • 143.
    Berggren, Karl-Fredrik
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik.
    Yakymenko, Iryna
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik.
    Simulation of the time-dependent behavior of QCA circuits2006Ingår i: Quantum Cellular Automata: Theory, Experimentation and Prospects / [ed] Macucci, Massimo, London: Imperial Press , 2006, s. -300Kapitel i bok, del av antologi (Övrigt vetenskapligt)
    Abstract [en]

    The Quantum Cellular Automaton (QCA) concept represents an attempt to break away from the traditional three-terminal device paradigm that has dominated digital computation. Since its early formulation in 1993 at Notre Dame University, the QCA idea has received significant attention and several physical implementations have been proposed. This book provides a comprehensive discussion of the simulation approaches and the experimental work that have been undertaken on the fabrication of devices capable of demonstrating the fundamentals of QCA action. Complementary views of future perspectives for QCA technology are presented, highlighting a process of realistic simulation and of targeted experiments that can be assumed as a model for the evaluation of future device proposals.

  • 144.
    Berggren, Magnus
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad Fysik. Linköpings universitet, Tekniska högskolan.
    Bergman, Peder
    Linköpings universitet, Institutionen för fysik, kemi och biologi. Linköpings universitet, Tekniska högskolan.
    Fagerström, Jan
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska högskolan.
    Inganäs, Olle
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad Fysik. Linköpings universitet, Tekniska högskolan.
    Andersson, Mats
    Chalmers Tekniska Högskola.
    Weman, Helge
    Linköpings universitet, Institutionen för fysik, kemi och biologi. Linköpings universitet, Tekniska högskolan.
    Granström, Magnus
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Tillämpad Fysik. Linköpings universitet, Tekniska högskolan.
    Stafström, Sven
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska högskolan.
    Wennerström, O
    Chalmers Tekniska Högskola.
    Hjertberg, T
    Chalmers Tekniska Högskola.
    Controlling inter-chain and intra-chain excitations of a poly(thiophene) derivative in thin films1999Ingår i: Chemical Physics Letters, ISSN 0009-2614, E-ISSN 1873-4448, Vol. 304, nr 1-2, s. 84-90Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The decay of photoexcitations in polythiophene chains has been studied in solid solutions of the polymer from room temperature to 4 K. A strong blue shift of the emission spectrum is observed in the polymer blend, as compared to the homopolymer. Dispersion of the polythiophene suppresses the non-radiative processes, which are suggested to be correlated to close contacts of polymer chains. Quantum chemistry modeling of the excited state distributed on two chains corroborate this conclusion.

  • 145.
    Bergman, Anders
    et al.
    Uppsala University.
    Burkert, Till
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik.
    Sanyal, Biplab
    Uppsala University.
    Frota-Pessôa, Sonia
    Universidade de Saõ Paulo.
    Nordström, Lars
    Uppsala University.
    Ruban, Andrei V.
    Royal Institute of Technology.
    Simak, Sergey
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik.
    Eriksson, Olle
    Uppsala University.
    Magnetic properties of Fe /Co(001) superlattices from first- principles theory2006Ingår i: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 74, s. 174409-1-174409-7Artikel i tidskrift (Refereegranskat)
  • 146.
    Bergman, Peder
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial.
    Pozina, Galia
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial.
    Monemar, Bo
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial.
    Dalfors, J.
    Sernelius, Bo
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik.
    Holtz, Per-Olof
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial.
    Amano, H.
    Akasaki, I.
    Radiative recombination in InGaN/GaN multiple quantum well2000Ingår i: ICSCRM 99,1999, 2000, s. 1571-Konferensbidrag (Refereegranskat)
  • 147.
    Beyer, Jan
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Funktionella elektroniska material. Linköpings universitet, Tekniska högskolan.
    Buyanova, Irina
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Funktionella elektroniska material. Linköpings universitet, Tekniska högskolan.
    Sernelius, Bo E.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska högskolan.
    Suraprapapich, S
    Department of Electrical and Computer Engineering, University of California at San Diego, La Jolla, USA .
    Tu, C. W.
    Department of Electrical and Computer Engineering, University of California, San Diego, La Jolla, California, USA .
    Chen, Weimin
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Funktionella elektroniska material. Linköpings universitet, Tekniska högskolan.
    Strong suppression of spin generation at a Fano resonance in a semiconductor nanostructure2012Manuskript (preprint) (Övrigt vetenskapligt)
    Abstract [en]

    We observe remarkable, complete suppression of spin generation under optical excitation in a thin InAs/GaAs wetting layer close to the light-hole excitonic resonance, leading to zero electron spin polarization as monitored by adjacent InAs quantum dots. The suppression is attributed to efficient spin relaxation/scattering at the Fano resonance between the light-hole exciton states and the heavy-hole continuum of the wetting layer. The complete suppression is found to remain effective up to temperatures exceeding 100 K.

  • 148.
    Beyer, Jan
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Funktionella elektroniska material. Linköpings universitet, Tekniska högskolan.
    Puttisong, Yuttapoom
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska högskolan.
    Buyanova, Irina
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Funktionella elektroniska material. Linköpings universitet, Tekniska högskolan.
    Suraprapapich, S.
    Department of Electrical and Computer Engineering, University of California, La Jolla, California 92093, USA.
    Tu, C. W.
    Department of Electrical and Computer Engineering, University of California, San Diego, La Jolla, California, USA .
    Chen, Weimin
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Funktionella elektroniska material. Linköpings universitet, Tekniska högskolan.
    Temperature dependence of dynamic nuclear polarization and its effect on electron spin relaxation and dephasing in InAs/GaAs quantum dots2012Ingår i: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 100, nr 14, s. 143105-Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Electron spin dephasing and relaxation due to hyperfine interaction with nuclear spins is studied in an InAs/GaAs quantum dot ensemble as a function of temperature up to 85 K, in an applied longitudinal magnetic field. The extent of hyperfineinduced dephasing is found to decrease, whereas dynamic nuclear polarization increases with increasing temperature. We attribute both effects to an accelerating electron spin relaxation through phonon-assisted electron-nuclear spin flip-flops driven by hyperfine interactions, which could become the dominating contribution to electron spin depolarization at high temperatures.

  • 149.
    Bingham, Robert
    et al.
    STFC Rutherford Appleton Lab, NJ USA .
    Eliasson, Bengt
    Ruhr University of Bochum, Germany .
    Mendonca, Tito
    IST Lisbon, Portugal .
    Stenflo, Lennart
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska högskolan.
    Biographical-Item: Padma Kant Shukla 1950-2013 Obituary in JOURNAL OF PLASMA PHYSICS, vol 79, issue , pp 119-1192013Övrigt (Övrigt vetenskapligt)
    Abstract [en]

    n/a

  • 150.
    Bingham, Robert
    et al.
    Rutherford Appleton Lab, England .
    Eliasson, Bengt
    Ruhr University of Bochum, Germany .
    Tito Mendonca, Jose
    Institute Super Tecn, Portugal .
    Stenflo, Lennart
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska högskolan.
    Ion acceleration by Alfven waves on auroral field lines2013Ingår i: Physica Scripta, ISSN 0031-8949, E-ISSN 1402-4896, Vol. 87, nr 5Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Observations of ion acceleration along auroral field lines at the boundary of the plasma sheet and tail lobe of the Earth show that the energy of the ions increases with decreasing density. The observations can be explained by ion acceleration through Landau resonance with kinetic Alfven waves (KAWs) such that k(A) . v(i) = omega(A), where k(A) is the wave vector, v(i) is the ion resonance velocity and omega(A) is the Alfven wave frequency. The ion resonance velocities are proportional to the Alfven velocity which increases with decreasing density. This is in agreement with the data if the process is occurring at the plasma sheet tail lobe boundary. A quasi-linear theory of ion acceleration by KAWs is presented. These ions propagate both down towards and away from the Earth. The paths of the Freja and Polar satellites indicate that the acceleration takes place between the two satellites, between 1Re and 5Re. The downward propagating ions develop a horseshoe-type of distribution which has a positive slope in the perpendicular direction. This type of distribution can produce intense lower hybrid wave activity, which is also observed. Finally, the filamentation of shear Alfven waves is considered. It may be responsible for large-scale density striations.

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