Instanton theory for bosons in disordered speckle potential

We study the tail of the spectrum for non-interacting bosons in a blue-detuned random speckle potential. Using an instanton approach we derive the asymptotic behavior of the density of states in d dimensions. The leading corrections resulting from fluctuations around the saddle point solution are obtained by means of the Gel'fand-Yaglom method generalized to functional determinants with zero modes. We find a good agreement with the results of numerical simulations in one dimension. The effect of weak repulsive interactions in the Lifshitz tail is also discussed.Comment: 12 pages, 3 figures, revtex

Enterprise Risk Management, Corporate Governance And Systemic Risk: Some Research Perspectives

The general goal of Enterprise Risk Management (ERM) processes is to generate economic value through the coverage of firm business risk, on the one hand, and by exploiting the positive side of uncertainty conditions, on the other hand. The increasing attention attributed to ERM in the creation of economic value has led to even greater interactions between risk management mechanisms and the corporate governance system. In other words, in the last two decades, the relationships between corporate governance and ERM increased since the ERM processes have been considered more and more as critical drivers to combine strategic objectives with relative low volatility of company performance. The basic idea is that a good corporate governance system must deal about specific risks along with their interactions and, at the same time, the firm’s business risk as a whole. Moreover, an efficient and effective ERM system provides clear information about linkages between strategic opportunities and risk exposure and offers tools able to manage in an optimal way the negative side of business risk (or downside risk) as wellas its positive side (or upside risk). Accordingly, extant studies concerning the relationships between ERM and corporate governance have been focusing on a micro-level of analyses (i.e., the individual organization) and, specifically, on a firm’s benefits that stem from the adoption of proper ERM processes that are consistent with corporate governance goals and are able to sustain the increase of economic value while maintaining a bearable business risk over time. From our initial analyses, a gap in literature arises. We argue that the interdependence between ERM and corporate governance may be analyzed from a broader point of view as well (i.e., the firm and its task environment composed by its suppliers, customers, and partners). In particular, our research idea is to enlarge traditional studies about interrelations between corporate governance and ERM taking into account whether such interrelations could be a driver of risk transfer from the focal organization to other organizations that belong to its task environment. Moreover, this study aims to deepen the mechanisms by which the transfer of risk from a focal organization to its task environment may foster the emergence of systemic risk, i.e., a macro risk coming from domino and/or network effects. Therefore, our paper aims to find new research areas by combining micro and macro issues tied to corporate governance, ERM and systemic risk. The starting point of our work is the three following assumptions: 1) The compliance of a firm to ERM processes as well as to corporate governance rules implies the reduction as much as possible of firm business risk; 2) The reduction of the firm business risk leads to externalizing the firm business risk through risk-sharing mechanisms; 3) The risk-sharing may arise like a driver of systemic risk especially in those industries featured by strong network interrelations. Starting from the above assumptions, the paper goal is to open a new research area which combines four academic fields (ERM, corporate governance, corporate finance, and macro-finance). So far, our initial findings tell us that the following research questions arise: RQ1: What are the conditions under which the transfer of business risk towards organizations that belong to a firm task environment is likely to become a source of systemic risk in a specific industry? RQ2: How does the capital structure of a focal firm affect its propensity to transfer business risk not only to commercial but also to financial stakeholders included in firm task environment? RQ3: How does the transfer of business risk influence the capital cost of the focal firm as well as of the organizations that absorbed such risk

Positive or negative voting premium: what happened to private benefits in Italy?

A large body of research deals with voting premium as a proxy of private benefit of control. Almost all of them find positive voting premium, in particular in Italy. Therefore appears interesting to ask what is the current status of private benefits of control in Italy in the last decade (2007-2017). Surprisingly, we show three major findings: i) reduction of non-voting share in the Italian scenario; ii) prevalence of negative voting rights premium more than positive ones, thus conflicting with the assumption and the observations by other researchers; iii) limits of the voting premium method. Our aim is that this study, despite its limitations, may encourage further researches focused on the analysis of the improvement and the change in the Italian corporate governance. The article points out that interesting evidence already exists, although still much remains to do in the future

Wave function correlations and the AC conductivity of disordered wires beyond the Mott-Berezinskii law

In one-dimensional disordered wires electronic states are localized at any energy. Correlations of the states at close positive energies and the AC conductivity $\sigma(\omega)$ in the limit of small frequency are described by the Mott-Berezinskii theory. We revisit the instanton approach to the statistics of wave functions and AC transport valid in the tails of the spectrum (large negative energies). Applying our recent results on functional determinants, we calculate exactly the integral over gaussian fluctuations around the exact two-instanton saddle point. We derive correlators of wave functions at different energies beyond the leading order in the energy difference. This allows us to calculate corrections to the Mott-Berezinskii law (the leading small frequency asymptotic behavior of $\sigma(\omega)$) which approximate the exact result in a broad range of $\omega$. We compare our results with the ones obtained for positive energies.Comment: 7 pages, 3 figure

Why does the Jeans Swindle work?

When measuring the mass profile of any given cosmological structure through internal kinematics, the distant background density is always ignored. This trick is often refereed to as the "Jeans Swindle". Without this trick a divergent term from the background density renders the mass profile undefined, however, this trick has no formal justification. We show that when one includes the expansion of the Universe in the Jeans equation, a term appears which exactly cancels the divergent term from the background. We thereby establish a formal justification for using the Jeans Swindle.Comment: 5 pages, 2 figures, Accepted for publication in MNRAS Letter

Atom-molecule theory of broad Feshbach resonances

We derive the atom-molecule theory for an atomic gas near a broad Feshbach resonance, where the energy dependence of the atom-molecule coupling becomes crucial for understanding experimental results. We show how our many-body theory incorporates the two-atom physics exactly. In particular, we calculate the magnetic moment of a two-component gas of ^{6}Li atoms for a wide range of magnetic fields near the broad Feshbach resonance at about 834 Gauss. We find excellent agreement with the experiment of Jochim et al. [Phys. Rev. Lett. 91, 240402 (2003)].Comment: 4 pages, 2 figure

Crossover temperature of Bose-Einstein condensation in an atomic Fermi gas

We show that in an atomic Fermi gas near a Feshbach resonance the crossover between a Bose-Einstein condensate of diatomic molecules and a Bose-Einstein condensate of Cooper pairs occurs at positive detuning, i.e., when the molecular energy level lies in the two-atom continuum. We determine the crossover temperature as a function of the applied magnetic field and find excellent agreement with the experiment of Regal et al. [Phys. Rev. Lett. 92, 040403 (2004)] that has recently observed this crossover temperature.Comment: 4 pages, 2 figure

Components Qualification for a Possible use in the Mu2e Calorimeter Waveform Digitizers

The Mu2e experiment at Fermilab searches for the charged flavor violating conversion of a muon into an electron in the Coulomb field of a nucleus. The detector consists of a straw tube tracker and a CSI crystal electromagnetic calorimeter, both housed in a superconducting solenoid. Both the front-end and the digital electronics, located inside the cryostat, will be operated in vacuum under a 1 T magnetic field, having to sustain the high flux of neutrons and ionizing particles coming from the muons stopping target. These harsh experimental conditions make the design of the calorimeter waveform digitizer quite challenging. All the selected commercial devices must be tested individually and qualified for radiation hardness and operation in high magnetic field. At the moment the expected particles flux and spectra at the digitizers location are not completely simulated and we are using initial rough estimates to select the components for the first prototype. We are gaining experience in the qualification procedures using the selected components but the choice will be frozen only when dose and neutron flux simulations will be completed. The experimental results of the first qualification campaign are presented.Comment: TWEPP 2016 - Topical Workshop on Electronics for Particle Physics, 26-30 September 2016, Karlsruhe Institute of Technology (KIT