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H. B. Nielsen

Publications and source records attributed to H. B. Nielsen.

At least 73 records · Page 4Linked to original sources

New Bound States of several Top-quarks bound by Higgs Exchange

It is suggested that there is a fine tuning principle remarkably arranging the top-quark Yukawa coupling to be just so as to make the mass $m_{12}$ of a bound state of 6 top + 6 anti-top quarks become very small. The value of the top Yukawa needed for Higgs and gluon etc. exchanges just binding the 12 quarks to make this mass zero is $g_t|_{m_{12}=0} =1.01 \pm 0.15$, while the experimental running top Yukawa coupling is $g_t = .94$.

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Cosmological Constant in SUGRA Models Inspired by Degenerate Vacua

It is well known that global symmetries protect local supersymmetry and a zero value for the cosmological constant in no--scale supergravity. A particular breakdown of these symmetries, which ensures the vanishing of the vacuum energy density, leads to the natural realisation of the multiple point principle (MPP). In the MPP inspired SUGRA models the cosmological constant is naturally tiny.

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Fixed point scenario in the Two Higgs Doublet Model inspired by degenerate vacua

We consider the renormalisation group flow of Higgs and Yukawa couplings within the simplest non--supersymmetric two Higgs doublet extension of the Standard Model (SM). In this model the couplings are adjusted so that the multiple point principle (MPP) assumption, which implies the existence of a large set of degenerate vacua at some high energy scale $Λ$, is realised. When the top quark Yukawa coupling at the scale $Λ$ is large, the solutions of RG equations in this MPP inspired 2 Higgs Doublet Model (2HDM) converge to quasi--fixed points. We analyse the Higgs spectrum and couplings in the quasi--fixed point scenario and compute a theoretical upper bound on the lightest Higgs boson mass. When the scale $Λ$ is low, the coupling of the SM--like Higgs scalar to the top quark can be significantly larger in the considered model than in the SM, resulting in the enhanced production of Higgs bosons at the LHC.

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Smallness of the cosmological constant and the multiple point principle

In this talk we argue that the breakdown of global symmetries in no--scale supergravity (SUGRA), which ensures the vanishing of the vacuum energy density near the physical vacuum, leads to a natural realisation of the multiple point principle (MPP). In the MPP inspired SUGRA models the cosmological constant is naturally tiny.

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Localization of Gauge Fields and Monopole Tunnelling

We study the dynamical localization of a massless gauge field on a lower-dimensional surface (2-brane). In flat space, the necessary and sufficient condition for this phenomenon is the existence of confinement in the bulk. The resulting configuration is equivalent to a dual Josephson junction. This duality leads to an interesting puzzle, as it implies that a localized massless theory, even in the Abelian case, must become confining at exponentially large distances. Through the use of topological arguments we clarify the physics behind this large-distance confinement and identify the instantons of the brane world-volume theory that are responsible for its appearance. We show that they correspond to the (condensed) bulk magnetic charges (monopoles), that occasionally tunnel through the brane and induce weak confinement of the brane theory. We consider the possible generalization of this effect to higher dimensions and discuss phenomenological bounds on the confinement of electric charges at exponentially large distances within our Universe.

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Homolumo Gap and Matrix Model

We discuss a dynamical matrix model by which probability distribution is associated with Gaussian ensembles from random matrix theory. We interpret the matrix M as a Hamiltonian representing interaction of a bosonic system with a single fermion. We show that a system of second-quantized fermions influences the ground state of the whole system by producing a gap between the highest occupied eigenvalue and the lowest unoccupied eigenvalue.

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Constrained Gauge Fields from Spontaneous Lorentz Violation

Spontaneous Lorentz violation realized through a nonlinear vector field constraint of the type $A_μA^μ=M^{2}$ ($M$ is the proposed scale for Lorentz violation) is shown to generate massless vector Goldstone bosons, gauging the starting global internal symmetries in arbitrary relativistically invariant theories. The gauge invariance appears in essence as a necessary condition for these bosons not to be superfluously restricted in degrees of freedom, apart from the constraint due to which the true vacuum in a theory is chosen by the Lorentz violation. In the Abelian symmetry case the only possible theory proves to be QED with a massless vector Goldstone boson naturally associated with the photon, while the non-Abelian symmetry case results in a conventional Yang-Mills theory. These theories, both Abelian and non-Abelian, look essentially nonlinear and contain particular Lorentz (and $CPT$) violating couplings when expressed in terms of the pure Goldstone vector modes. However, they do not lead to physical Lorentz violation due to the simultaneously generated gauge invariance.

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Proceedings to the 10th Workshop 'What Comes Beyond the Standard Models', Bled, July 17. - 27., 2007, Slovenia

Contents: 1. Finestructure Constants at the Planck Scale from Multiple Point Principle (D.L.Bennett, L.V. Laperashvili and H.B. Nielsen) 2. Random Dynamics in Starting Levels (D. Bennett, A. Kleppe in H.B. Nielsen), 3. Families of Quarks and Leptons and Their Mass Matrices from the Approach Unifying Spins and Charges: Prediction for the Fourth Family (G. Bregar, M. Breskvar, D. Lukman and N.S. Mankoc Borstnik) 4. Fermion-Fermion and Boson-Boson Amplitudes: Surprising Similarities (V.V. Dvoeglazov) 5. Antisymmetric Tensor Fields, 4-Vector Fields, Indefinite Metrics and Normalization (V.V. Dvoeglazov) 6. Quantum Gates and Quantum Algorithms with Clifford Algebra Technique (M. Gregoric and N.S. Mankoc Borstnik) 7. From the Starting Lagrange Density to the Effective Fields for Spinors in the Approach Unifying Spins and Charges (N.S. Mankoc Borstnik) 8. New Generations of Particles in the Universe (M.Yu. Khlopov) 9. A Subversive View of Modern 'Physics' (R. Mirman) 10. Mass Spectra are Inherent in Geometry: an Analysis Using the Only Conformal Group Allowing a Universe (R. Mirman) 11. Complex Action, Prearrangement for Future and Higgs Broadening (H.B. Nielsen and M. Ninomiya) 12. Discussion on Dark Matter Candidates from the Approach Unifying Spins and Charges (G. Bregar and N.S. Mankoc Borstnik) 13. Discussion Section Summary on Dark Matter Particle Properties (M.Yu. Khlopov and N.S. Mankoc Borstnik)

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Involution requirement on a boundary makes massless fermions compactified on a finite flat disk mass protected

The genuine Kaluza-Klein-like theories--with no fields in addition to gravity--have difficulties with the existence of massless spinors after the compactification of some space dimensions \cite{witten}. We proposed (Phys. Lett. B 633 (2006)771) such a boundary condition for spinors in 1+5 compactified on a flat disk that ensures masslessness of spinors in d=1+3 as well as their chiral coupling to the corresponding background gauge field (which solves equations of motion for a free field linear in the Riemann curvature). In this paper we study the same toy model: M^{(1+3)} x M^{(2)}, looking this time for an involution which transforms a space of solutions of Weyl equations in d=1+5 from the outside of the flat disk in x^5 and x^6 into its inside, allowing massless spinor of only one handedness--and accordingly assures mass protection--and of one charge--1/2--and infinitely many massive spinors of the same charge, chirally coupled to the corresponding background gauge field. We reformulate the operator of momentum so that it is Hermitean on the vector space of spinor states obeying the involution boundary condition.

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Proceedings to the 9th Workshop 'What Comes Beyond the Standard Models', Bled, September 16. - 26., 2006, Slovenia

Contents: 1. Child Universes in the Laboratory (S. Ansoldi and E.I. Guendelman) 2. Relation between Finestructure Constants at the Planck Scale from Multiple Point Principle (D.L. Bennett, L.V. Laperashvili and H.B. Nielsen) 3. On the Origin of Families of Fermions and Their Mass Matrices -- Approximate Analyses of Properties of Four Families Within Approach Unifying Spins and Charges (M. Breskvar, D. Lukman and N.S. Mankoc Borstnik) 4. Cosmoparticle Physics: Cross-disciplinary Study of Physics Beyond the Standard Model (M.Yu. Khlopov) 5. Discussion Section on 4th Generation (M.Yu. Khlopov) 6. Involution Requirement on a Boundary Makes Massless Fermions Compactified on a Finite Flat Disk Mass Protected (N.S. Mankoc Borstnik and H.B. Nielsen) 7. How Can Group Theory be Generalized so Perhaps Providing Further Information About Our Universe? (R. Mirman) 8. FutureDependent Initial Conditions from Imaginary Part in Lagrangian (H.B. Nielsen and M. Ninomiya) 9. Coupling Self-tuning to Critical Lines From Highly Compact Extra Dimensions (K. Petrov)

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Generalized dual symmetry of nonabelian theories and the freezing of α_s

The quantum Yang-Mills theory, describing a system of fields with non-dual (chromo-electric g) and dual (chromo-magnetic \tilde g) charges and revealing the generalized dual symmetry, is developed by analogy with the Zwanziger formalism in QED. The renormalization group equations (RGEs) for pure nonabelian theories are analysed for both constants, α= g^2 / 4πand \tildeα= {\tilde g}^2 / 4π. The pure SU(3) \times \widetilde{SU(3)} gauge theory is investigated as an example. We consider not only monopoles, but also dyons. The behaviour of the total SU(3) β-function is investigated in the whole region of α\equiv α_s: 0 \le α< \infty. It is shown that this β-function is antisymmetric under the interchange α\longleftrightarrow 1/αand is given by the well-known perturbative expansion not only for α\ll 1, but also for α\gg 1. Using an idea of the Maximal Abelian Projection by t' Hooft, we considered the formation of strings - the ANO flux tubes - in the Higgs model of scalar monopole (or dyon) fields. In this model we have constructed the behaviour of the β-function in the vicinity of the point α= 1, where it acquires a zero value. Considering the phase transition points at α\approx 0.4 and α\approx 2.5, we give the explanation of the freezing of α_s. The evolution of α_s^{-1}(μ) and the behaviour of V_{eff}(μ) are investigated for both, perturbative and non-perturbative regions of QCD. It was shown that the effective potential has a minimum, ensured by the dual sector of QCD. The gluon condensate F^2_0, corresponding to this minimum, is predicted: F^2_0 \approx 0.15 GeV^4, in agreement with the well-known results.

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Flipped SU(5), see-saw scale physics and degenerate vacua

We investigate the requirement of the existence of two degenerate vacua of the effective potential as a function of the Weinberg-Salam Higgs scalar field norm, as suggested by the multiple point principle, in an extension of the Standard Model including see-saw scale physics. Results are presented from an investigation of an extension of the Standard Model to the gauge symmetry group SU(3)_C\times SU(2)_L\times U(1)'\times \tilde U(1), where two groups U(1)' and \tilde U(1) originate at the see-saw scale M_{SS}, when heavy (right-handed) neutrinos appear. The consequent unification of the group SU(3)_C\times SU(2)_L\times U(1)' into the flipped SU(5) at the GUT scale leads to the group SU(5)\times \tilde U(1). We assume the position of the second minimum of the effective potential coincides with the fundamental scale, here taken to be the GUT scale. We solve the renormalization group equations in the one-loop approximation and obtain a top-quark mass of 171\pm 3 GeV and a Higgs mass of 129\pm 4 GeV, in the case when the Yukawa couplings of the neutrinos are less than half that of the top quark at the GUT scale.

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Dark matter from encapsulated atoms

We propose that dark matter consists of collections of atoms encapsulated inside pieces of an alternative vacuum, in which the Higgs field vacuum expectation value is appreciably smaller than in the usual vacuum. The alternative vacuum is supposed to have the same energy density as our own. Apart from this degeneracy of vacuum phases, we do not introduce any new physics beyond the Standard Model. The dark matter balls are estimated to have a radius of order 20 cm and a mass of order $10^{11}$ kg. However they are very difficult to observe directly, but inside dense stars may expand eating up the star and cause huge explosions (gamma ray bursts). The ratio of dark matter to ordinary baryonic matter is estimated to be of the order of the ratio of the binding energy per nucleon in helium to the difference between the binding energies per nucleon in heavy nuclei and in helium. Thus we predict approximately five times as much dark matter as ordinary baryonic matter!

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Crypto-baryonic Dark Matter

It is proposed that dark matter could consist of compressed collections of atoms (or metallic matter) encapsulated into, for example, 20 cm big pieces of a different phase. The idea is based on the assumption that there exists at least one other phase of the vacuum degenerate with the usual one. Apart from the degeneracy of the phases we only assume Standard Model physics. The other phase has a Higgs VEV appreciably smaller than in the usual electroweak vacuum. The balls making up the dark matter are very difficult to observe directly, but inside dense stars may expand eating up the star and cause huge explosions (gamma ray bursts). The ratio of dark matter to ordinary baryonic matter is expressed as a ratio of nuclear binding energies and predicted to be about 5.

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On the smallness of the cosmological constant in SUGRA models

In no--scale supergravity global symmetries protect local supersymmetry and a zero value for the cosmological constant. We consider the breakdown of these symmetries and present a minimal SUGRA model motivated by the multiple point principle, in which the total vacuum energy density is naturally tiny. In order to reproduce the observed value of the cosmological constant and preserve gauge coupling unification, an additional pair of $5+\bar{5}$--plets of superfields has to be included in the particle content of the considered model. These extra fields have masses of the order of the supersymmetry breaking scale; so they can be detected at future colliders. We also discuss the supersymmetry breakdown and possible solution of the cosmological constant problem by MPP in models with an enlarged gauge symmetry.

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Proceedings to the 8th Workshop 'What Comes Beyond the Standard Models', Bled, July 19. - 29., 2005, Slovenia

Contents: 1. Can MPP Together with Weinberg-Salam Higgs Provide Cosmological Inflation? (D.L. Bennett and H.B. Nielsen) 2. Conserved Charges in 3d Gravity With Torsion (M. Blagojevic and B. Cvetkovic) 3. Mass Matrices of Quarks and Leptons in the Approach Unifying Spins and Charges (A. Borstnik Bracic and N.S. Mankoc Borstnik) 4. Dark Matter From Encapsulated Atoms (C.D. Froggatt and H.B. Nielsen) 5. Dirac Sea for Bosons Also and SUSY for Single Particles (Y. Habara, H.B. Nielsen and M. Ninomiya) 6. Searching for Boundary Conditions in Kaluza-Klein-like Theories (D. Lukman, N.S. Mankoc Borstnik and H. B. Nielsen) 7. Second Quantization of Spinors and Clifford Algebra Objects (N.S. Mankoc Borstnik and H. B. Nielsen) 8. Are there Interesting Problems That Could Increase Understanding of Physics and Mathematics? (R. Mirman) 9. Noncommutative Nonsingular Black Holes (P. Nicolini) 10. Compactified Time and Likely Entropy -- World Inside Time Machine: Closed Time-like Curve (H.B. Nielsen and M. Ninomiya) + Astri Kleppe's Song.

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