Excited heavy tetraquarks with hidden charm

The masses of the excited heavy tetraquarks with hidden charm are calculated within the relativistic diquark-antidiquark picture. The dynamics of the light quark in a heavy-light diquark is treated completely relativistically. The diquark structure is taken into account by calculating the diquark-gluon form factor. New experimental data on charmonium-like states above open charm threshold are discussed. The obtained results indicate that X(3872), Y(4260), Y(4360), Z(4248), Z(4433) and Y(4660) could be tetraquark states with hidden charm.Comment: 11 page

Liquidity, technological opportunities, and the stage distribution of venture capital investments

This paper explores the determinants of the stage distribution of European venture capital investments from 1990 to 2011. Consistent with liquidity risk theory, we find that the likelihood of investing in earlier stages increases relative to all private equity investments during liquidity crisis years. While liquidity is the main driver of acquisition investments and, to some extent, of expansion financings, technological opportunities are overall the main driver of early and late stage venture capital investments. In contrast to the dotcom crash, the recent financial crisis negatively affected the relative likelihood of expansion investments, but not of early and late stage investments

Challenges of open innovation: the paradox of firm investment in open-source software

Open innovation is a powerful framework encompassing the generation, capture, and employment of intellectual property at the firm level. We identify three fundamental challenges for firms in applying the concept of open innovation: finding creative ways to exploit internal innovation, incorporating external innovation into internal development, and motivating outsiders to supply an ongoing stream of external innovations. This latter challenge involves a paradox, why would firms spend money on R&D efforts if the results of these efforts are available to rival firms? To explore these challenges, we examine the activity of firms in opensource software to support their innovation strategies. Firms involved in open-source software often make investments that will be shared with real and potential rivals. We identify four strategies firms employ – pooled R&D/product development, spinouts, selling complements and attracting donated complements – and discuss how they address the three key challenges of open innovation. We conclude with suggestions for how similar strategies may apply in other industries and offer some possible avenues for future research on open innovation

Masses of light tetraquarks and scalar mesons in the relativistic quark model

Masses of the ground state light tetraquarks are dynamically calculated in the framework of the relativistic diquark-antidiquark picture. The internal structure of the diquark is taken into account by calculating the form factor of the diquark-gluon interaction in terms of the overlap integral of the diquark wave functions. It is found that scalar mesons with masses below 1 GeV: f_0(600) (\sigma), K^*_0(800) (\kappa), f_0(980) and a_0(980) agree well with the light tetraquark interpretation.Comment: 9 pages, Report-no adde

SU(2) WZW Theory at Higher Genera

We compute, by free field techniques, the scalar product of the SU(2) Chern-Simons states on genus > 1 surfaces. The result is a finite-dimensional integral over positions of ``screening charges'' and one complex modular parameter. It uses an effective description of the CS states closely related to the one worked out by Bertram. The scalar product formula allows to express the higher genus partition functions of the WZW conformal field theory by finite-dimensional integrals. It should provide the hermitian metric preserved by the Knizhnik-Zamolodchikov-Bernard connection describing the variations of the CS states under the change of the complex structure of the surface.Comment: 44 pages, IHES/P/94/10, Latex fil

Odderon and Pomeron from the Vacuum Correlator Method

Glueball masses with J<=7 are computed both for C=+1 and C=-1 using the string Hamiltonian derived in the framework of the Vacuum Correlator Method. No fitting parameters are used, and masses are expressed in terms of string tension $\sigma$ and effective value of $\alpha_s$. We extend the calculations done for J<=3 using the same Hamiltonian, which provided glueball masses in good agreement with existing lattice data, to higher mass states. It is shown that 3^{--}, 5^{--} and 7^{--} states lie on the odderon trajectories with the intercept around or below 0.14. Another odderon trajectory with 3g glueballs of Y-shape, corresponds to 11% higher masses and low intercept. These findings are in agreement with recent experimental data, setting limits on the odderon contribution to the exclusive $\gamma p$ reactions.Comment: 16 pages. Journal version. To be published in Phys.Lett.

A purely algebraic construction of a gauge and renormalization group invariant scalar glueball operator

This paper presents a complete algebraic proof of the renormalizability of the gauge invariant $d=4$ operator $F_{\mu\nu}^2(x)$ to all orders of perturbation theory in pure Yang-Mills gauge theory, whereby working in the Landau gauge. This renormalization is far from being trivial as mixing occurs with other $d=4$ gauge variant operators, which we identify explicitly. We determine the mixing matrix $Z$ to all orders in perturbation theory by using only algebraic arguments and consequently we can uncover a renormalization group invariant by using the anomalous dimension matrix $\Gamma$ derived from $Z$. We also present a future plan for calculating the mass of the lightest scalar glueball with the help of the framework we have set up.Comment: 17 page

Attentive Learning of Sequential Handwriting Movements: A Neural Network Model

Defense Advanced research Projects Agency and the Office of Naval Research (N00014-95-1-0409, N00014-92-J-1309); National Science Foundation (IRI-97-20333); National Institutes of Health (I-R29-DC02952-01)

Damping scales of neutralino cold dark matter

The lightest supersymmetric particle, most likely the neutralino, might account for a large fraction of dark matter in the Universe. We show that the primordial spectrum of density fluctuations in neutralino cold dark matter (CDM) has a sharp cut-off due to two damping mechanisms: collisional damping during the kinetic decoupling of the neutralinos at about 30 MeV (for typical neutralino and sfermion masses) and free streaming after last scattering of neutralinos. The last scattering temperature is lower than the kinetic decoupling temperature by one order of magnitude. The cut-off in the primordial spectrum defines a minimal mass for CDM objects in hierarchical structure formation. For typical neutralino and sfermion masses the first gravitationally bound neutralino clouds have to have masses above 10^(-7) solar masses.Comment: 13 pages, 5 figures; typos corrected; accepted by Physical Review

The spatio-relational nature of urban innovation systems: Universities, knowledge intensive business service firms, and collaborative networks

The need to better identify the spatio-relational nature of urban innovation systems and spaces is increasingly acknowledged. The aim of this paper, therefore, is to provide an enhanced understanding of the knowledge networks existing between urban Knowledge Intensive Business Services firms (KIBS) and universities, which are often key components of such systems and spaces. Drawing on an analysis of urban KIBS firms and universities in the UK, it is found that the nature of firms, the location in which they are based, and the research intensity of their university partners are important determinants of the spatiality and localisation of the networks they form. The results show that the smallest urban KIBS firms have the highest propensity to engage in local links with universities, suggesting that they rely most significantly on their own urban innovation system for collaborative network ties. Keywords : innovation systems; urban innovation spaces; knowledge-based development; proximity; networks; KIBS; universities