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  • 1.
    Hansson, Johan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Moderna Fysiken på 15 Minuter2017Bok (Övrig (populärvetenskap, debatt, mm))
  • 2.
    Hansson, Johan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Quantivity?2017Rapport (Refereegranskat)
  • 3.
    Hansson, Johan
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Francois, Stephane
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Testing Quantum Gravity2017Ingår i: International Journal of Modern Physics D, ISSN 0218-2718, Vol. 26, 1743003Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The search for a theory of quantum gravity is the most fundamental problem in all of theoretical physics, but there are as yet no experimental results at all to guide this endeavor. What seems to be needed is a pragmatic way to test if gravitation really occurs between quantum objects or not. In this paper, we suggest such a potential way out of this deadlock, utilizing macroscopic quantum systems; superfluid helium, gaseous Bose–Einstein condensates and “macroscopic” molecules. It turns out that true quantum gravity effects — here defined as observable gravitational interactions between truly quantum objects — could and should be seen (if they occur in nature) using existing technology. A falsification of the low-energy limit in the accessible weak-field regime would also falsify the full theory of quantum gravity, making it enter the realm of testable, potentially falsifiable theories, i.e. becoming real physics after almost a century of pure theorizing. If weak-field gravity between quantum objects is shown to be absent (in the regime where the approximation should apply), we know that gravity then is a strictly classical phenomenon absent at the quantum level.Read More: http://www.worldscientific.com/doi/abs/10.1142/S0218271817430039

  • 4.
    Hansson, Johan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Black Holes: Anybody out there?2016Ingår i: Electronic Journal of Theoretical Physics, ISSN 1729-5254, E-ISSN 1729-5254, Vol. 13, nr 35, 91-94 s.Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Using analytical results from both general relativity and quantum mechanics weshow that physical black holes probably do not exist. This would actually be a boon totheoretical physics, for example as:i) General relativity would then be globally valid in the (classical) physical universe, due to itsnon-singular nature.ii) The black hole information paradox would vanish.iii) No event horizon would mean no Hawking radiation, resolving the causal paradox that foran outside observer it takes an infinite time for the black hole to form whereas it evaporates infinite time.Astrophysical applications that seem to require black holes (quasars/AGNs, some binarysystems, stellar motions near the center of our galaxy, etc) can still be fulfilled by compactbut non-singular masses, M..

  • 5.
    Hansson, Johan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    No-Go of Quantized General Relativity2016Ingår i: Advanced Studies in Theoretical Physics, ISSN 1313-1311, E-ISSN 1314-7609, Vol. 10, nr 8, 415-420 s.Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In this article we show: i) The impossibility of actively “quantizing” general relativity. ii) That the key to quantum gravity - a theory for “deducing” the macroscopic theory of general relativity - is to explain, from a fundamental microscopic theory, why the inertial mass is proportional to the gravitational mass, mi=mg = const, in the classical limit

  • 6.
    Hansson, Johan
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Francois, Stephane
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Testing Quantum Gravity2016Rapport (Refereegranskat)
  • 7.
    Hansson, Johan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Black Holes: Anybody out there?2015Rapport (Refereegranskat)
    Abstract [en]

    Using analytical results from both general relativity and quantummechanics we show that physical black holes probably do not exist.This would actually be a boon to theoretical physics, for example as:i) General relativity would then be globally valid in the (classical)physical universe, due to its non-singular nature.ii) The black hole information paradox would vanish.iii) No event horizon would mean no Hawking radiation, resolving thecausal paradox that for an outside observer it takes an innite timefor the black hole to form whereas it evaporates in nite time.Astrophysical applications that seem to require black holes (quasars/AGNs,stellar motions near the center of our galaxy, etc) can still be fullledby compact but non-singular masses, M.

  • 8.
    Hansson, Johan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    No-Go of Quantized General Relativity2015Rapport (Refereegranskat)
  • 9.
    Hansson, Johan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    "Quantum machine" to solve quantum "measurement problem"?2015Ingår i: Advanced Studies in Theoretical Physics, ISSN 1313-1311, E-ISSN 1314-7609, Vol. 9, nr 5, 233-236 s.Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Recently a study of the rst superposed mechanical quantum object(\machine") visible to the naked eye was published [1]. However, as weshow, it turns out that if the object would actually be observed, i.e.would interact with an optical photon, the quantum behavior shouldvanish. This, the actual observation, has long been suspected in manyinterpretations of quantum mechanics to be what makes the transitionquantum ! classical, but so far it has not been available for direct ex-perimental study in a mechanical system. We show how any interaction,even a purely quantum one, of sucient strength can constitute a physi-cal \measurement" - essentially the emergence of an eectively classicalobject - active observation thus being a sucient but not necessary cri-terion. So it seems we have in this case of the \quantum machine" aunique possibility to study, and possibly solve, the long-standing \mea-surement problem" of quantum mechanics.

  • 10.
    Hansson, Johan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    The 10 Biggest Unsolved Problems in Physics2015Rapport (Refereegranskat)
  • 11.
    Hansson, Johan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    The 10 Biggest Unsolved Problems in Physics2015Ingår i: International Journal of Modern Physics and Applications, ISSN 2381-6945, Vol. 1, nr 1, 12-16 s.Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In 1900, the British physicist Lord Kelvin declared: “There is nothing new to discover in physics. All that remains is to more accurately measure its quantities.” In the same year quantum physics was born and three decades later it, and Einstein’s theory of relativity, had completely revolutionized and transformed physics. Today, hardly anyone would dare say that our knowledge of the universe, and everything in it, is almost complete. On the contrary, every new discovery appears to open a Pandora’s Box of larger and deeper issues. I have selected some of today’s biggest unsolved riddles in physics. Just like Moses, I stop arbitrarily at 10. Here follow these “Ten Com...plications” with a brief explanation/justification. They may be seen as a roadmap for future important work.

  • 12.
    Hansson, Johan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Microscopic gravity?2014Rapport (Refereegranskat)
  • 13.
    Hansson, Johan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Physical Origin of Elementary Particle Masses2014Ingår i: Electronic Journal of Theoretical Physics, ISSN 1729-5254, E-ISSN 1729-5254, Vol. 11, nr 30, 87-100 s.Artikel i tidskrift (Refereegranskat)
  • 14.
    Hansson, Johan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    “Quantum machine” to solve quantum “measurement problem”?2014Rapport (Refereegranskat)
  • 15.
    Hansson, Johan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Physical Origin of Elementary Particle Masses2013Rapport (Refereegranskat)
  • 16.
    Hansson, Johan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    On the Origin of Elementary Particle Masses2012Rapport (Refereegranskat)
  • 17.
    Hansson, Johan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Reality or locality?: Proposed test to decide how nature breaks Bell's inequality2012Ingår i: Physics Research International, ISSN 2090-2220, E-ISSN 2090-2239, Vol. 2012, 352543Artikel i tidskrift (Refereegranskat)
  • 18.
    Hansson, Johan
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Ponga, Anna
    LTU.
    Pulsars: Cosmic permanent “neutromagnets”?2011Ingår i: ISRN Astronomy and Astrophysics, ISSN 2090-4738, E-ISSN 2090-4746, Vol. 2011, nr Article ID 378493Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We argue that pulsars may be spin-polarized neutron stars, that is, cosmic permanent magnets. This would simply explain several observational facts about pulsars, including the “beacon effect” itself, that is, the static/stable misalignment of rotational and magnetic axes, the extreme temporal stability of the pulses, and the existence of an upper limit for the magnetic field strength, coinciding with the one observed in “magnetars.” Although our model admittedly is speculative, this latter fact seems to us unlikely to be pure coincidence.

  • 19.
    Hansson, Johan
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Lindkvist, Jesper
    Inhomogeneous structure formation may alleviate need for accelerating universe2010Ingår i: The Open Astronomy Journal, ISSN 1874-3811, E-ISSN 1874-3811, Vol. 3, 145-149 s.Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    When taking the real, inhomogeneous and anisotropic matter distribution in the semi-local universe into account, there may be no need to postulate an accelerating expansion of the universe despite recent type Ia supernova data. Local curvatures must be integrated (over all space) to obtain the global curvature of the universe, which seems to be very close to zero from cosmic microwave background data. As gravitational structure formation creates bound regions of positive curvature, the regions in between become negatively curved in order to comply with a vanishing global curvature. The actual dynamics of the universe is altered due to the self-induced inhomogeneities, again more prominently so as structure formation progresses. Furthermore, this negative curvature will increase as a function of time as structure formation proceeds, which mimics the effect of "dark energy" with negative pressure. Hence, the "acceleration" may be merely a mirage. We make a qualitative and semi-quantitative analysis, for pedagogical reasons using newtonian gravity corrected for special relativistic effects (which works surprisingly well) to corroborate and illustrate/visualize these statements. This article may be seen as an attempt to communicate to a larger number of people the necessity of starting to take seriously the real, observed inhomogeneous distribution and the nonlinearities of nonperturbative general relativity, and their impact on the dynamics and behavior of the cosmos instead of allowing an oversimplified cosmological model to generate a consensus world-view of a cosmos allegedly dominated by mysterious dark energy.

  • 20.
    Hansson, Johan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Newtonian quantum gravity2010Ingår i: Physics essays, ISSN 0836-1398, Vol. 23, nr 1, 53-56 s.Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A Newtonian approach to quantum gravity is studied. At least for weak gravitational fields, it should be a valid approximation. Such an approach can be used to point out problems and prospects inherent in a more exact theory of quantum gravity, yet to be discovered. Newtonian quantum gravity, e.g., shows promise for prohibiting black holes altogether (which would eliminate singularities and also solve the black hole information paradox), gives gravitational radiation even in the spherically symmetric case, and supports nonlocality (quantum entanglement). Its predictions should also be testable at length scales well above the "Planck scale" by high-precision experiments feasible with existing technology.

  • 21.
    Hansson, Johan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Nonlinear gauge interactions: a possible solution to the "measurement problem" in quantum mechanics2010Ingår i: Physics essays, ISSN 0836-1398, Vol. 23, nr 2, 237-241 s.Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Two fundamental and unsolved problems in physics are as follows: (i) the resolution of the "measurement problem" in quantum mechanics and (ii) the quantization of strongly nonlinear (non-Abelian) gauge theories. The aim of this paper is to suggest that these two problems might be linked and that a mutual simultaneous solution to both might exist. We propose that the mechanism responsible for the "collapse of the wave function" in quantum mechanics is the nonlinearities already present in the theory via non-Abelian gauge interactions. Unlike all other models of spontaneous collapse, our proposal is, to the best of our knowledge, the only one that does not introduce any new elements into the theory. A possible experimental test of the model would be to compare the coherence lengths-here defined as the distance over which the quantum mechanical superposition is still valid-e.g., electrons and photons in a double-slit experiment. The electrons should have a finite coherence length, while photons should have a much longer coherence length (in principle infinite, if gravity-a very weak effect indeed unless we approach the Planck scale-is ignored).

  • 22.
    Hansson, Johan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    The "Proton Spin Crisis" - a Quantum Query2010Ingår i: Progress in Physics, ISSN 1555-5534, E-ISSN 1555-5615, Vol. 3, 51-52 s.Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The "proton spin crisis" was introduced in the late 1980s, when the EMC-experiment revealed that little or nothing of a proton's spin seemed to be carried by its quarks. The main objective of this paper is to point out that it is wrong to assume that the proton spin, as measured by completely di erent experimental setups, should be the same in all circumstances, an assumption explicitly made in all present theoretical treatments of the "crisis". As spin is a genuine quantum property, without any objective existence outside its measuring apparatus context, proper account of quantum mechanical measurement theory must be taken.

  • 23.
    Hansson, Johan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Aspects of nonrelativistic quantum gravity2009Ingår i: Brazilian journal of physics, ISSN 0103-9733, E-ISSN 1678-4448, Vol. 39, nr 4, 707-710 s.Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A nonrelativistic approach to quantum gravity is studied. At least for weak gravitational fields it should be a valid approximation. Such an approach can be used to point out problems and prospects inherent in a more exact theory of quantum gravity, yet to be discovered. Nonrelativistic quantum gravity, e.g., shows promise for prohibiting black holes altogether (which would eliminate singularities and also solve the black hole information paradox), gives gravitational radiation even in the spherically symmetric case, and supports non-locality (quantum entanglement). Its predictions should also be testable at length scales well above the "Planck scale", by high-precision experiments feasible with existing technology.

  • 24.
    Hansson, Johan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Big Bang på 15 minuter - Stora skrällen2008Ingår i: Allt om Vetenskap, ISSN 1652-3318, nr 4, 104-108 s.Artikel i tidskrift (Övrig (populärvetenskap, debatt, mm))
  • 25.
    Hansson, Johan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Kosmologin på 15 minuter - Läran om allt2008Ingår i: Allt om Vetenskap, ISSN 1652-3318, nr 1, 104-108 s.Artikel i tidskrift (Övrig (populärvetenskap, debatt, mm))
  • 26.
    Hansson, Johan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Kvantgravitationen på 15 minuter - Den gäckande teorin2008Ingår i: Allt om Vetenskap, ISSN 1652-3318, nr 3, 104-108 s.Artikel i tidskrift (Övrig (populärvetenskap, debatt, mm))
  • 27.
    Hansson, Johan
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Zernell, Lasse
    Allt om Vetenskap.
    Preonstjärnor - Äntligen något nytt på himlen2008Ingår i: Allt om Vetenskap, ISSN 1652-3318, nr 8, 82-89 s.Artikel i tidskrift (Övrig (populärvetenskap, debatt, mm))
  • 28.
    Hansson, Johan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Strängteorin på 15 minuter - Teorin om allt... eller inget?2008Ingår i: Allt om Vetenskap, ISSN 1652-3318, nr 2, 104-108 s.Artikel i tidskrift (Övrig (populärvetenskap, debatt, mm))
  • 29.
    Hansson, Johan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Svarta hål på 15 minuter - Fysikens slut?2008Ingår i: Allt om Vetenskap, ISSN 1652-3318, nr 5, 104-108 s.Artikel i tidskrift (Övrig (populärvetenskap, debatt, mm))
  • 30.
    Hansson, Johan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    A hierarchy of cosmic compact objects: without black holes2007Ingår i: Acta Physica Polonica B, ISSN 0587-4254, E-ISSN 1509-5770, Vol. 38, nr 1, 91-100 s.Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We make the case for the existence of a, hitherto unknown and unobserved, hierarchy of ever more compact cosmic objects in the universe. This hypothesis is based on i) the assumption of "elementary" particle sub-constituents on several levels below the presently known, inspired by Glashow's "blooming desert", ii) the existence of nearly scale-invariant density fluctuations in the early universe, e.g. as predicted by inflationary models, iii) our own previous theoretical work showing that a class of objects considerably more compact than previously thought possible in astrophysics can exist. We also give several independent arguments strongly pointing towards the non-existence of black holes. Some brief suggestions on observational signals due to the hierarchy, both in collected astronomical data and in possible future observations, concludes the paper.

  • 31.
    Hansson, Johan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Kaosteorin på 15 minuter - Världen är inget urverk2007Ingår i: Allt om Vetenskap, ISSN 1652-3318, nr 11, 104-108 s.Artikel i tidskrift (Övrig (populärvetenskap, debatt, mm))
  • 32.
    Hansson, Johan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Kvantfysiken på 15 minuter: världen är (o)sannolik2007Ingår i: Allt om Vetenskap, ISSN 1652-3318, nr 9, 106-109 s.Artikel i tidskrift (Övrig (populärvetenskap, debatt, mm))
  • 33. Sandin, Fredrik
    et al.
    Hansson, Johan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Observational legacy of preon stars: probing new physics beyond the CERN LHC2007Ingår i: Physical Review D. Particles and fields, ISSN 0556-2821, E-ISSN 1089-4918, Vol. 76, nr 12Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We discuss possible ways to observationally detect the superdense cosmic objects composed of hypothetical subconstituent fermions beneath the quark/lepton level, recently proposed by us. The characteristic mass and size of such objects depend on the compositeness scale, and their huge density cannot arise within a context of quarks and leptons alone. Their eventual observation would therefore be a direct vindication of physics beyond the standard model of particle physics, possibly far beyond the reach of the Large Hadron Collider (LHC), in a relatively simple and inexpensive manner. If relic objects of this type exist, they can possibly be detected by present and future x-ray observatories, high-frequency gravitational wave detectors, and seismological detectors. To have a realistic detection rate, i.e., to be observable, they must necessarily constitute a significant fraction of cold dark matter.

  • 34.
    Hansson, Johan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Partikelfysiken på 15 minuter - Vad är fundamentalt?2007Ingår i: Allt om Vetenskap, ISSN 1652-3318, Vol. 12, 104-108 s.Artikel i tidskrift (Övrig (populärvetenskap, debatt, mm))
  • 35.
    Hansson, Johan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Relativitetsteorin på 15 minuter: allt är inte alls relativt2007Ingår i: Allt om Vetenskap, ISSN 1652-3318, nr 10, 106-109 s.Artikel i tidskrift (Övrig (populärvetenskap, debatt, mm))
  • 36. Sandin, Fredrik
    et al.
    Hansson, Johan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    The observational legacy of preon stars: probing new physics beyond the LHC2007Rapport (Övrigt vetenskapligt)
    Abstract [en]

    We discuss possible ways to observationally detect the superdense cosmic objects composed of hypothetical sub-constituent fermions beneath the quark/lepton level, recently proposed by us. The characteristic mass and size of such objects depend on the compositeness scale, and their huge density cannot arise within a context of quarks and leptons alone. Their eventual observation would therefore be a direct vindication of physics beyond the standard model of particle physics, possibly far beyond the reach of the Large Hadron Collider (LHC), in a relatively simple and inexpensive manner. If relic objects of this type exist, they can possibly be detected by present and future x-ray observatories, high-frequency gravitational wave detectors, and seismological detectors. To have a realistic detection rate, i.e., to be observable, they must necessarily constitute a significant fraction of cold dark matter.

  • 37.
    Hansson, Johan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Newtonian Quantum Gravity2006Rapport (Övrigt vetenskapligt)
  • 38.
    Hansson, Johan
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Sandin, Fredrik
    Preon stars: a new class of cosmic compact objects2005Ingår i: Physics Letters B, ISSN 0370-2693, E-ISSN 1873-2445, Vol. 616, nr 1-2, 1-7 s.Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In the context of the standard model of particle physics, there is a definite upper limit to the density of stable compact stars. However, if a more fundamental level of elementary particles exists, in the form of preons, stability may be re-established beyond this limiting density. We show that a degenerate gas of interacting fermionic preons does allow for stable compact stars, with densities far beyond that in neutron stars and quark stars. In keeping with tradition, we call these objects "preon stars", even though they are small and light compared to white dwarfs and neutron stars. We briefly note the potential importance of preon stars in astrophysics, e.g., as a candidate for cold dark matter and sources of ultra-high energy cosmic rays, and a means for observing them.

  • 39.
    Hansson, Johan
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Sandin, Fredrik
    Preonstjärnor - en ny sorts himlakropp?2005Ingår i: Populär astronomi, ISSN 1650-7177, Vol. 4, nr 8, 8-13 s.Artikel i tidskrift (Övrig (populärvetenskap, debatt, mm))
  • 40.
    Hansson, Johan
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Sandin, Fredrik
    Stor som en kula men tyngre än jorden: Svenska forskare kan ha upptäckt de första kompakta objekten i universum på sjuttio år2005Ingår i: Forskning & Framsteg, ISSN 0015-7937, nr 7, 40-43 s.Artikel i tidskrift (Övrig (populärvetenskap, debatt, mm))
  • 41.
    Hansson, Johan
    et al.
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Olevik, David
    Türk, Christian
    Luleå tekniska universitet.
    Wiklund, Hanna
    Luleå tekniska universitet.
    Comment on "Measurement of quantum states of neutrons in the Earth's gravitational field"2003Ingår i: Physical Review D. Particles and fields, ISSN 0556-2821, E-ISSN 1089-4918, Vol. 68, nr 10, 1087011-13 s.Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    In the paper by Nesvizhevsky et al. [Phys. Rev. D 67, 102002 (2003)], it is argued that the lowest quantum state of neutrons in the Earth's gravitational field has been experimentally identified. While this is most likely correct, it is imperative to investigate all alternative explanations of the result in order to close all loopholes, as it is the first experiment ever claimed to have observed gravitational quantum states. Here we show that geometrical effects in the experimental setup can mimic the results attributed to gravity. Modifications of the experimental setup to close these possible loopholes are suggested.

  • 42.
    Hansson, Johan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Reply to comment on 'A Simple explanation of the nonappearance of physical gluons and quarks'2003Ingår i: Canadian journal of physics (Print), ISSN 0008-4204, E-ISSN 1208-6045, Vol. 81, 893-894 s.Artikel i tidskrift (Övrigt vetenskapligt)
    Abstract [en]

    This is the reply to a comment by Andreas Aste on a previous article of mine in Can.J.Phys. The counter-arguments used by Aste utilize a mathematical limit without physical meaning. We still contend that in QCD, the particles ``gluons'' and ``quarks'' are merely artifacts of an approximation method (the perturbative expansion) and are simply absent in the exact theory.

  • 43.
    Hansson, Johan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    The 'Proton spin crisis': A Quantum query2003Rapport (Övrigt vetenskapligt)
    Abstract [en]

    The "proton spin crisis" was introduced in the late 1980s, when the EMC-experiment revealed that little or nothing of a proton's spin seemed to be carried by its quarks. The main objective of this paper is to point out that it is wrong to assume that the proton spin, measured by completely different experimental setups, should be the same in all circumstances.

  • 44.
    Hansson, Johan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    A simple explanation of the nonappearance of physical gluons and quarks2002Ingår i: Canadian journal of physics (Print), ISSN 0008-4204, E-ISSN 1208-6045, Vol. 80, nr 9, 1093-1097 s.Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    We show that the nonappearance of gluons and quarks as physical particles is a rigorous and automatic result of the full, i.e., nonperturbative, nonabelian nature of the color interaction in quantum chromodynamics (QCD). This makes it, in general, impossible to describe the color field as a collection of elementary quanta (gluons). Neither can a quark be an elementary quantum of the quark field, as the color field of which it is the source is itself a source, making isolated noninteracting quarks, crucial for a physical particle interpretation, impossible. In geometrical language, the impossibility of quarks and gluons as physical elementary particles arises due to the fact that the color Yang-Mills space does not have a constant trivial curvature. In QCD, the particles "gluons" and "quarks" are merely artifacts of an approximation method (the perturbative expansion) and are simply absent in the exact theory. This also coincides with the empirical, experimental evidence

  • 45.
    Dugne, Jean-Jacques
    et al.
    Laboratoire de Physique Corpusculaire, Université Blaise Pascal Clermont-Ferrand.
    Fredriksson, Sverker
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Hansson, Johan
    Preon trinity: a schematic model of leptons, quarks and heavy vector bosons2002Ingår i: Europhysics letters, ISSN 0295-5075, E-ISSN 1286-4854, Vol. 60, nr 2, 188-194 s.Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Quarks, leptons and heavy vector bosons are suggested to be composed of stable spin- (1/2) preons, existing in three flavours, combined according to simple rules. Straightforward consequences of an SU(3) preon-flavour symmetry are the conservation of three lepton numbers, oscillations and decays between some neutrinos, and the mixing of the d and s quarks, as well as of the vector fields W0 and B0. We find a relation between the Cabibbo and Weinberg mixing angles, and predict new (heavy) leptons, quarks and vector bosons, some of which might be observable at the Fermilab Tevatron and the future CERN LHC. A heavy neutrino might even be visible in existing data from the CERN LEP facility.

  • 46.
    Hansson, Johan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    A possible experimental test to decide if quantum mechanical randomness is due to deterministic chaos in the underlying dynamics2000Rapport (Övrigt vetenskapligt)
    Abstract [en]

    A simple experiment using radioactive decay is proposed to test the possibility of a determinsistic, but chaotic, origin of quantum mechanical randomness.

  • 47.
    Hansson, Johan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    A simple solution to color confinement2000Rapport (Övrigt vetenskapligt)
    Abstract [en]

    We show that color confinement is a direct result of the nonabelian, i.e. nonlinear, nature of the color interaction in quantum chromodynamics. This makes it in general impossible to describe the color field as a collection of elementary quanta (gluons). A quark cannot be an elementary quanta of the quark field, as the color field of which it is the source is itself a source hence making isolated (noninteracting) quarks impossible. In geometrical language, the impossibility of quarks and gluons as physical particles arises due to the fact that the color Yang-Mills space does not have a constant trivial curvature.

  • 48.
    Hansson, Johan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Nonlinear gauge interactions: a solution to the 'measurement problem' in quantum mechanics?2000Rapport (Övrigt vetenskapligt)
    Abstract [en]

    We propose that the mechanism responsible for the ``collapse of the wave function" (or "decoherence" in its broadest meaning) in quantum mechanics is the nonlinearities already present in the theory via nonabelian gauge interactions. Unlike all other models of spontaneous collapse, our proposal is, to the best of our knowledge, the only one which does not introduce any new elements into the theory. Indeed, unless the gauge interaction nonlinearities are not used for exactly this purpose, one must then explain why the violation of the superposition principle which they introduce does not destroy quantum mechanics. A possible experimental test of the model would be to compare the coherence lengths for, e.g., electrons and photons in a double-slit experiment. The electrons should have a finite coherence length, while photons should have a much longer (in principle infinite) coherence length.

  • 49.
    Anselmino, M.
    et al.
    Dipertemento di Fisica Teoria, Universita di Torino and INFS.
    Boglione, M.
    Department of Physics and Astronomy, Vrije Universitet Amsterdam.
    Hansson, Johan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Murgia, F.
    Institute Nazionale Fisica Nucleare, Seizone di Cagliari.
    Predictions for single spin asymmetries in ℓ parrow -> π X and γ * parrow -> π X2000Ingår i: European Physical Journal C, ISSN 1434-6044, E-ISSN 1434-6052, Vol. 13, nr 3, 519-526 s.Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Predictions for the single transverse spin asymmetry AN in semi-inclusive DIS processes are given; non-negligible values of AN may arise from spin effects in the fragmentation of a polarized quark into a final hadron with a transverse momentum ěc k⊥ with respect to the jet axis, the so-called Collins effect. The elementary single spin asymmetry of the fragmenting quark has been fixed in a previous paper, by fitting data on parrow p -> π X, and by assuming that the QCD factorization theorem holds also when transverse momenta are taken into account. The predictions given here are based on the assumption that the Collins effect is the only cause of the observed single spin asymmetries in parrow p -> π X. Eventual spin and ěc k⊥ dependences in the quark distribution functions, the so-called Sivers effect, are also discussed.

  • 50. Fredriksson, Sverker
    et al.
    Enström, Daniel
    Hansson, Johan
    Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik, Materialvetenskap.
    Ekelin, Svante
    Kungliga tekniska högskolan, KTH.
    Nicolaidis, A.
    Is dark matter made up of massive quark objects?1999Ingår i: Dark matter in astrophysics and particle physics 1998: proceedings of the Second International Conference on Dark Matter in Astrophysics and Particle Physics / [ed] Hans Volker Klapdor-Kleingrothaus ; L. Baudis, Bristol: IOP Publishing Ltd , 1999, 651-658 s.Konferensbidrag (Refereegranskat)
    Abstract [en]

    We suggest that dark matter is made up of massive quark objects that have survived from the Big Bang, representing the ground state of "baryonic'' matter. Hence, there was no overall phase transition of the original quark matter, but only a split-up into smaller objects. We speculate that normal hadronic matter comes about through enforced phase transitions when such objects merge or collide, which also gives rise to the cosmic gamma-ray bursts.

12 1 - 50 av 69
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