The stochastic gravitational-wave background from massive black hole binary systems: implications for observations with Pulsar Timing Arrays

Massive black hole binary systems, with masses in the range ~10^4-10^10 \msun, are among the primary sources of gravitational waves in the frequency window ~10^-9 Hz - 0.1 Hz. Pulsar Timing Arrays (PTAs) and the Laser Interferometer Space Antenna (LISA) are the observational means by which we will be able to observe gravitational radiation from these systems. We carry out a systematic study of the generation of the stochastic gravitational-wave background from the cosmic population of massive black hole binaries. We consider a wide variety of assembly scenarios and we estimate the range of signal strength in the frequency band accessible to PTAs. We show that, taking into account the uncertainties surrounding the actual key model parameters, the amplitude lies in the interval h_c(f = 10^-8 Hz)~5x10^-16 - 8x10^-15. The most optimistic predictions place the signal level at a factor of ~3 below the current sensitivity of Pulsar Timing Arrays, but within the detection range of the complete Parkes PTA for a wide variety of models, and of the future Square-Kilometer-Array PTA for all the models considered here. We also show that at frequencies >10^-8 Hz the frequency dependency of the generated background follows a power-law significantly steeper than f^-2/3, that has been considered so far. Finally we show that LISA observations of individual resolvable massive black hole binaries are complementary and orthogonal to PTA observations of a stochastic background from the whole population in the Universe. In fact, the detection of gravitational radiation in both frequency windows will enable us to fully characterise the cosmic history of massive black holes.Comment: 21 pages, 14 figures, minor revisions, accepted for publication in MNRA

Venous obstruction of the thigh

A case of femoral vein thrombosis is described by 3D spiral CT

Localization of effective actions in open superstring field theory: small Hilbert space

We consider the algebraic effective couplings for open superstring massless modes in the framework of the $A_\infty$ theory in the small Hilbert space. Focusing on quartic algebraic couplings, we reduce the effective action of the $A_\infty$ theory to the Berkovits one where we have already shown that such couplings are fully computed from contributions at the boundary of moduli space, when the massless fields under consideration are appropriately charged under an ${\cal N}\!=\!2$ $R$-symmetry. Here we offer a proof of localization which is in the small Hilbert space. We also discuss the flat directions of the obtained quartic potentials and give evidence for the existence of exactly marginal deformations in the $D3/D(-1)$ system in the framework of string field theory.Comment: 34 pages, no figures. V2: Improved presentation, typos correcte

Localization of effective actions in open superstring field theory

We consider the construction of the algebraic part of D-branes tree-level effective action from Berkovits open superstring field theory. Applying this construction to the quartic potential of massless fields carrying a specific worldsheet charge, we show that the full contribution to the potential localizes at the boundary of moduli space, reducing to elementary two-point functions. As examples of this general mechanism, we show how the Yang-Mills quartic potential and the instanton effective action of a $Dp/D(p-4)$ system are reproducedComment: 30 pages (incl appendix). No figure

Rating and ranking firms with fuzzy expert systems: the case of Camuzzi

In this paper we present a real-life application of a fuzzy expert system aimed at rating and ranking firms. Unlike standard DCF models, it integrates financial, strategic and business determinants and processes both quantitative and qualitative variables. Twenty-one value drivers are defined, concerning the target firm (strategic assets in place and expected financial performance), the acquisition (synergies, quality of management) and the sector (intensity of competition, entry barriers). Their combination via “if-then” rules leads to the definition of an output represented by a real number in the interval [0,1]. Such a number expresses the value-generating power of the target firm inclusive of synergies with the bidder (Strategic Enterprise Value). The system may be used for rating and ranking firms operating in the same sector. A regression analysis using hostile takeovers multiples may be employed to translate the score into price. The real-life case refers to Camuzzi (a natural gas distributor), acquired by Enel, the Italian ex monopolist of electric energy.Corporate finance, firm, rating, ranking, expert system, fuzzy, evaluation

Project valuation and investment decisions: CAPM versus arbitrage

This paper shows that (i) project valuation via disequilibrium NPV+CAPM contradicts valuation via arbitrage pricing, (ii) standard CAPM-minded decision makers may fail to profit from arbitrage opportunities, (iii) standard CAPM-based valuation violates value additivity. As a consequence, the standard use of CAPM for project valuation and decision making should be reconsidered.Investment, valuation, CAPM, arbitrage, disequilibrium NPV

Correct or incorrect application of CAPM? Correct or incorrect decisions with CAPM?

This paper focuses on inconsistencies arising from the use of NPV and CAPM for capital budgeting. It shows that (i) CAPM capital budgeting decision-making based on disequilibrium NPV is deductively inferred by the Capital Asset Pricing Model, (ii) the use of the disequilibrium NPV is widespread in finance both as a decision rule and as a valuation tool, (iii) the disequilibrium NPV does not guarantee additivity nor consistency with arbitrage pricing, so that it is unreliable for valuation, (iv) Magni’s (2002, 2007a, forthcoming) criticism of the NPV criterion refers to the disequilibrium NPV, and De Reyck’s (2005) project valuation method, on the basis of which Magni’s criticism to NPV is objected, leaves decision makers open to arbitrage losses and incorrect decisions.Corporate finance; investment analysis; Net Present Value; Capital Asset Pricing Model; disequilibrium; decision; valuation; nonadditivity; arbitrage

A Sum&Discount method for appraising firms:An illustrative example

This paper presents a new way of valuing firms and measuring residual income. The method, originally introduced in Magni (2000a, 2000b, 2000c, 2001), is here renamed lost-capital paradigm. In order to enhance comprehension the presentation relies on a very simple numerical example which shows that the new paradigm of residual income enjoys a property of abnormal earnings aggregation, according to which the NPV (and therefore the market value) of the firm does not change if each residual income changes, as long as the (uncapitalized) sum of all residual incomes do not change. While radically different from the standard residual income, the difference between the two notions is equal to the interest accrued on the past cumulated standard residual incomes, which has interesting implications for incentive compensation.Firm valuation, residual income, lost capital, Discount&Sum, Sum&Discount, incentive compensation

Rating and ranking firms with fuzzy expert systems: the case of Camuzzi

In this paper we present a real-life application of a fuzzy expert system aimed at rating and ranking firms. Unlike standard DCF models, it integrates financial, strategic and business determinants and processes both quantitative and qualitative variables. Twenty-one value drivers are defined, concerning the target firm (strategic assets in place and expected financial performance), the acquisition (synergies, quality of management) and the sector (intensity of competition, entry barriers). Their combination via “if-then” rules leads to the definition of an output represented by a real number in the interval [0,1]. Such a number expresses the valuegenerating power of the target firm inclusive of synergies with the bidder (Strategic Enterprise Value). The system may be used for rating and ranking firms operating in the same sector. A regression analysis using hostile takeovers multiples may be employed to translate the score into price. The real-life case refers to Camuzzi (a natural gas distributor), acquired by Enel, the Italian ex monopolist of electric energy.Corporate finance, firm, rating, ranking, expert system, fuzzy logic, evaluation

An alternative approach to firms’ evaluation: expert systems and fuzzy logic

Discounted Cash Flow techniques are the generally accepted methods for valuing firms. Such methods do not provide explicit acknowledgment of the value determinants and overlook their interrelations. This paper proposes a different method of firm valuation based on fuzzy logic and expert systems. It does represent a conceptual transposition of Discounted Cash Flow techniques but, unlike the latter, it takes explicit account of quantitative and qualitative variables and their mutual integration. Financial, strategic and business aspects are considered by focusing on twenty-nine value drivers that are combined together via “if-then” rules. The output of the system is a real number in the interval [0,1], which represents the value-creation power of the firm. To corroborate the model a sensitivity analysis is conducted. The system may be used for rating and ranking firms as well as for assessing the impact of managers’ decisions on value creation and as a tool of corporate governance.Firms’ evaluation, fuzzy logic, expert system, rating, acquisition, sensitivity analysis