Bound-state Picture Research Articles

The dark universe: Primordial black hole ⇋ dark graviton gas connection

We study the possible correspondence between 5-dimensional primordial black holes and massive 5-dimensional KK gravitons as dark matter candidate within the recently proposed dark dimension scenario that addresses the cosmological hierarchy problem. First, we show that in the local universe a population of 5-dimensional black holes with MBH∼7×1013g would be practically indistinguishable from a KK tower of dark gravitons with mDM∼50keV. Second, we connect the mass increase of 5-dimensional black holes and the related temperature decrease with the cooling of the tower of massive spin-2 KK excitations of the graviton. The dark gravitons are produced at a mass ∼1−50GeV and the bulk of their mass shifts down to roughly 1−100keV today. The cooling of the system proceeds via decay to lighter gravitons without losing much total mass density, resembling the intra-tower decays that characterize the cosmological evolution of the dynamical dark matter framework. We associate the intra-tower decays of the graviton gas with the black hole growth through accretion. We also discuss that the primordial black hole ⇋ dark graviton gas connection can be nicely explained by the bound state picture of black holes in terms of gravitons.

String theory in with mixed flux: semiclassical and 1-loop phase in the S-matrix

We present a semiclassical derivation of the tree-level and 1-loop dressing phases in the massive sector of string theory on supplemented by Ramond–Ramond and Neveu–Schwarz–Neveu–Schwarz 3-form fluxes. In analogy with the case, we use the dressing method to obtain scattering solutions for dyonic giant magnons which allows us to determine the semiclassical bound-state S-matrix and its 1-loop correction. We also find that the 1-loop correction to the dyonic giant magnon energy vanishes. Looking at the relation between the bound-state picture and elementary magnons in terms of the fusion procedure we deduce the elementary dressing phases. In both the semiclassical and 1-loop cases we find agreement with recent proposals from finite-gap equations and unitarity cut methods. Further, we find consistency with the finite-gap picture by determining the resolvent for the dyonic giant magnon from the semiclassical bosonic scattering data.

Giant magnon solution and dispersion relation in string theory in [formula omitted] with mixed flux

We address the question of the exact form of the dispersion relation for light-cone string excitations in string theory in AdS3×S3×T4 with mixed R–R and NS–NS 3-form fluxes. The analogy with string theory in AdS5×S5 suggests that in addition to the data provided by the perturbative near-BMN expansion and symmetry algebra considerations there is another source of information for the dispersion relation – the semiclassical giant magnon solution. In earlier work in arXiv:1303.1037 and arXiv:1304.4099 we found that the symmetry algebra constraints, which are consistent with a perturbative expansion, do not completely determine the form of the dispersion relation. The aim of the present paper is to fix the dispersion relation by constructing a generalisation of the known dyonic giant magnon soliton on S3 to the presence of a non-zero NS–NS flux described by a WZ term in the string action (with coefficient q). We find that the angular momentum of this soliton gets shifted by a term linear in world-sheet momentum p. We also discuss the symmetry algebra of the string light-cone S-matrix and show that the exact dispersion relation, which should have the correct perturbative BMN and semiclassical giant magnon limits, should also contain such a linear momentum term. The simplicity of the resulting bound-state picture provides a strong argument in favour of this dispersion relation.

Spin dynamics in the electron-doped Kondo insulatorYb1−xZrxB12(x=0.2)

Electron doping of the Kondo insulator ${\text{YbB}}_{12}$ has been achieved by substitution of tetravalent Zr in the newly synthesized ${\text{Yb}}_{0.8}{\text{Zr}}_{0.2}{\text{B}}_{12}$ solid solution. Neutron-scattering measurements of the spin dynamics are reported, together with electrical resistivity and ac magnetic-susceptibility data. Zr doping transforms the spin-gap spectral response into a pseudogap shape and makes its temperature evolution much smoother than in the ${\text{Yb}}_{1\ensuremath{-}x}{\text{Lu}}_{x}{\text{B}}_{12}$ family studied previously. The results obtained are discussed in connection with the local bound-state picture for the Kondo insulator.

Strong and radiative decays of the scalarsf0(980)anda0(980)in a hadronic molecule approach

We analyze the electromagnetic and strong decay properties of the light scalars ${a}_{0}(980)$ and ${f}_{0}(980)$ within a hadronic molecule interpretation. Both scalars are discussed within a covariant and gauge invariant model which also allows for finite size effects due to their spatially extended structure in the $K\overline{K}$-bound state picture. Allowing for ${f}_{0}\mathrm{\text{\ensuremath{-}}}{a}_{0}$ mixing we also study its influence on the radiative decays ${f}_{0}/{a}_{0}\ensuremath{\rightarrow}\ensuremath{\gamma}\ensuremath{\gamma}$, ${f}_{0}/{a}_{0}\ensuremath{\rightarrow}\ensuremath{\gamma}\ensuremath{\omega}$, and ${f}_{0}/{a}_{0}\ensuremath{\rightarrow}\ensuremath{\gamma}\ensuremath{\rho}$ as well as the $\ensuremath{\phi}$ production of the ${f}_{0}$ and ${a}_{0}$. Furthermore, we apply our formalism to describe the strong ${f}_{0}\ensuremath{\rightarrow}\ensuremath{\pi}\ensuremath{\pi}$ and ${a}_{0}\ensuremath{\rightarrow}\ensuremath{\pi}\ensuremath{\eta}$ decay properties.

Restricted and unrestricted Hartree-Fock calculations of conductance for a quantum point contact

Very short quantum wires (quantum contacts) exhibit a conductance structure at a value of conductance close to $0.7 \times 2e^2/h$. It is believed that the structure arises due to the electron-electron interaction, and it is also related to electron spin. However details of the mechanism of the structure are not quite clear. Previously we approached the problem within the restricted Hartree-Fock approximation. This calculation demonstrated a structure similar to that observed experimentally. In the present work we perform restricted and unrestricted Hartree-Fock calculations to analyze the validity of the approximations. We also consider dependence of the effect on the electron density in leads. The unrestricted Hartree-Fock method allows us to analyze trapping of the single electron within the contact. Such trapping would result in the Kondo model for the ``0.7 structure''. The present calculation confirms the spin-dependent bound state picture and does not confirm the Kondo model scenario.

Radiative decays of excited Lambda Q baryons in the bound state picture.

It is shown that, in the bound state picture, the ${\ensuremath{\Lambda}}_{c}(2593)\ensuremath{\rightarrow}{\ensuremath{\Lambda}}_{c}\ensuremath{\gamma}$ and ${\ensuremath{\Lambda}}_{c}(2625)\ensuremath{\rightarrow}{\ensuremath{\Lambda}}_{c}\ensuremath{\gamma}$ decays are severely suppressed. On the other hand, for their bottom counterparts, which are predicted to have masses of 5900 and 5926 MeV, respectively, they may have significant radiative branching ratios. The ${\ensuremath{\Lambda}}_{b}(5926)\ensuremath{\rightarrow}{\ensuremath{\Lambda}}_{b}\ensuremath{\gamma}$ mode possibly dominates over the strong decay mode, while the ${\ensuremath{\Lambda}}_{b}(5900)$ resonance lies below the strong decay threshold and can only decay radiatively. The isospin allowed ${\ensuremath{\Lambda}}_{Q}^{**}\ensuremath{\rightarrow}{\ensuremath{\Sigma}}_{Q}\ensuremath{\gamma}$ mode is expected to be small.

Charmed strange pentaquarks in the large Nc limit.

The properties of pentaquarks containing a heavy antiquark and strange quarks are studied in the bound state picture. In the flavor SU(3) limit, there are many pentaquark states with the same binding energy. When the SU(3) symmetry-breaking effects are included, however, three states become particularly stable due to a ``Gell-Mann--Okubo mechanism.'' They are the Q\ifmmode\bar\else\textasciimacron\fi{}suud and Q\ifmmode\bar\else\textasciimacron\fi{}sudd states discussed by Lipkin, and a previously unstudied Q\ifmmode\bar\else\textasciimacron\fi{}ssud state. These states will have ${\mathit{J}}^{\mathit{P}}$=1/${2}^{+}$ and their masses are estimated. These states, if they exist, may be seen in experiments in the near future. \textcopyright{} 1996 The American Physical Society.

Excited heavy baryons in the bound state picture.

The orbitally excited heavy quark baryons are studied in the Callan Klebanov bound state model with heavy spin symmetry. First, a compact description of the large $N_c$, infinite heavy quark mass bound state wavefunctions and the collective quantization is given. In order to study the kinematical corrections due to finite masses we motivate an approximate Schrodinger-like equation for the bound state. The effective potential in this equation is compared with the quadratic approximation (spherical harmonic oscillator) to it. This oscillator approximation is seen to be not very accurate. It is noted that the present experimental information cannot be even qualitatively understood with the usual light sector chiral Lagrangian containing only light pseudoscalar mesons. The addition of light vector mesons helps to overcome this problem.

The decay B-bar0--> pi +l- nu to probe Vbu.

The semileptonic B decay, B-bar /sup 0/..--> pi../sup +/l/sup -/..nu.., is studied in a nonrelativistic picture by treating the pion correctly as a quasi-Nambu-Goldstone boson. The branching ratio is much larger than the value predicted by a two-body bound-state picture for the pion. This decay at the UPSILON(4S) peak in e/sup +/e/sup -/ annihilation will be one of the best suited processes to determine the Kobayashi-Maskawa mixing-matrix element V/sub b//sub u/.

Formula omitted] is not larger than [formula omitted]: determination of the B decay constant from the B ∗-B mass difference

The B meson decay constant ƒ B is determined from the recent experimental measurement of the B ∗-B mass difference. The estimate is made in the one-gluon exchange approximation to the hyperfine splitting in the nonrelativistic two-body bound state picture. If the QCD running coupling α S relevant to bū(d̄) binding is set equal to unity, ƒ B is (89±3±7) MeV. if α S is equated to a value consistent with the K ∗-K mass splitting, ƒ B is (53±2±4) MeV. Both are within the range of values predicted by the previous phenomenological analysis and MIT bag model calculations.

Composite W bosons and the ϱ-parameter in weak interactions

The ratio of the neutral to charged current Fermi constant ϱ is considered in models in which the weak bosons are bound states of two spin 1 2 constituents. Due to electromagnetic effects ϱ differs slightly from one. We estimate the magnitude of this effect adopting a nonrelativistic bound state picture of the W bosons. One obtains Δϱ = ϱ − 1 ∼ 0.01–0.04, dependending on the potential which confines the W constituents. Finally, we comment on the mass of color-exotic W bosons which appear in some models.

Magnetic behavior of cubic laves phase RMn 2 ( rmR = Gd, DyandHo) compounds

Magnetization studies have been carried out on the cubic Laves phase (C15) type) intermetallic compounds GdMn 2, DyMn 2 and HoMn 2 at various applied fields in the temperature range 4.2 to 300 K. All compounds show evidence of magnetic ordering at low temperatures. A peak in the magnetization versus temperature curve is observed in zero field cooled samples of GdMn 2 and DyMn 2 but not in HoMn 2. This is taken to imply ferrimagnetic ordering between the rare earth and Mn moments. The Mn moment is estimated to be approximately 2μ B in GdMn 2. It appears that Mn carried no localized moment in HoMn 2. An anomaly in magnetization of GdMn 2 is observed around 95 K. The Mn moment appears to decrease in RMn 2 compounds while crossing the rare earth series from Gd to Ho. No Mn moment is known in hexagonal Laves phases (C14 type) compounds ErMn 2 and TmMn 2. A virtual bound state picture of Mn-3d electrons is suggested to explain the structure change and the Mn moment collapse in the RMn 2 compounds.

New approach to the theory of coupled πNN-NN systems: (II). Further elaborations and relativistic extensions

We continue our investigation into the theory of coupled πNN-NN systems in succession of an earlier work, in which practical equations and unitarity have been established for all the pertinent amplitudes. First, the equivalence of our theory with that of Mizutani and Koltun is proved. Then, the question of whether theories which adopt the bound-state picture are appropriate for the description of systems of pions and nucleons is carefully discussed. We also show how the equations should be modified when we include the non-pole contribution to the πN P 11 channel. Finally, we extend our equations to include relativity and show how to arrive at numerically solvable equations, with relativistic invariance guaranteed. In the NN sector, these equations contain the two time orderings of the OPEP in a correct manner.

Resistivity and magnetoresistance anisotropy associated with s, p impurities in ferromagnetic Ni and Co

The authors have measured the electrical resistivity between 4.2K and 300K, and the longitudinal and transverse magnetoresistance at 4.2K, of several dilute Co and Ni based alloys containing various s, p impurities such as Sn and Sb. The deviations from Matthiessen's rule (DMR) derived from the resistivity data have been analysed in terms of the two current model of Campbell et al. (1968) and values for alpha (the ratio of spin up to spin down resistivities at the impurity site), mu (the same ratio at host sites) and D (the coefficient of the spin mixing term) estimated. The bulk of these data yield alpha approximately=1 for these impurities, as expected on the basis of a simple virtual bound state picture. The magnetoresistance data also yield values of alpha close to 1, but there are systematic differences between experiment and the predictions of the two current model.

Radiative decays of 2++ and 1++ mesons

Radiative decays of tensor and axial mesons are considered in the framework of a previously proposed scheme, where the basic currents ofSU4 are dominated by vector mesons and exhibit a quark structure asymptotically. Agreement is found with previousSU3 estimates. The decay rates for ψ′ → γχ1,2 also agree with experiments and nonrelativistic estimates. Conversely, the χ1,2 → γJ/ψ widths have been found smaller by about a factor of two than those obtained in the n.r. bound-state picture. Our results are also compared with those previously obtained for the χ0-meson.

Interacting virtual state approach to magnetically ordered state of transition metals

A new theory of the magnetically ordered state in transition metal based on a localized virtual bound state picture is proposed. Applications to the spin density wave state of Cr and the antiferromagnetic-to-ferromagnetic transition in FeRh are presented.

A dynamical treatment of radiative transitions in the charmonium picture

A dynamical scheme is proposed to resolve the problem of radiative transitions among the new particles within the quark-antiquark bound state picture. Contrary to the conventional treatments, here the proton is not coupled to the free quarks but is taken to be dominated by the spectrum of mesons which enter the off-mass shell hadronic vertices. The hadronic couplings are, in turn, calculated through the overlaps of their wave functions. The over-all normalization for the strength of hadronic couplings is obtained by requiring the elastic form factor at zero momentum to be one. The resulting values for the radiative widths are considerably smaller than the conventionally calculated ones and are in agreement with experiment.

The structure functions of regge recurrences and dual light-cone behaviour

We present spin-averaged deep inelastic structure functions of particles on a Regge trajectory in terms of the structure function of its lowest-lying member. They are extracted from a dual-model ansatz for Compton scattering off two particles which leads to canonical scaling. Part of the result is confirmed in the Bethe-Salpeter bound-state picture. We discuss the implications of our results for deep inelastic e+e+ annihilation where inclusive resonance production plays an important role.

Study of infra-red divergent terms in the bound-state picture

The infra-red divergent terms of the vertex function and the self-energy function within the renormalization program are studied in the way they depend upon the external potential. The structural dependence of the potential is treated insome detail. The observable photon mass due to the presence of the potential is explicity calculated in two-dimensional quantum electrodynamics.