13,292 research outputs found

    The merger boom: an overview

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    Consolidation and merger of corporations ; Corporations ; Public policy

    Are hostile takeovers different?

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    Consolidation and merger of corporations ; Corporations ; Stockholders

    The Eighteenth Century

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    This chapter has four sections: 1. Prose and General; 2. The Novel; 3. Poetry; 4. Drama. Section 1 is by Steven Lynn; section 2 is by Elles Smallegoor; section 3 is by David Shuttleton; section 4 is by Marjean Purinton

    A model for projectile fragmentation

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    A model for projectile fragmentation is developed whose origin can be traced back to the Bevalac era. The model positions itself between the phenomenological EPAX parametrization and transport models like "Heavy Ion Phase Space Exploration" (HIPSE) model and antisymmetrised molecular dynamics (AMD) model. A very simple impact parameter dependence of input temperature is incorporated in the model which helps to analyze the more peripheral collisions. The model is applied to calculate the charge, isotopic distributions, average number of intermediate mass fragments and the average size of largest cluster at different Z_{bound} of different projectile fragmentation reactions at different energies.Comment: Talk given by Gargi Chaudhuri at the 11th International Conference on Nucleus-Nucleus Collisions (NN2012), San Antonio, Texas, USA, May 27-June 1, 2012. 10 pages, 7 figure

    Quantum Monte Carlo Calculations of Light Nuclei Using Chiral Potentials

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    We present the first Green's function Monte Carlo calculations of light nuclei with nuclear interactions derived from chiral effective field theory up to next-to-next-to-leading order. Up to this order, the interactions can be constructed in a local form and are therefore amenable to quantum Monte Carlo calculations. We demonstrate a systematic improvement with each order for the binding energies of A=3A=3 and A=4A=4 systems. We also carry out the first few-body tests to study perturbative expansions of chiral potentials at different orders, finding that higher-order corrections are more perturbative for softer interactions. Our results confirm the necessity of a three-body force for correct reproduction of experimental binding energies and radii, and pave the way for studying few- and many-nucleon systems using quantum Monte Carlo methods with chiral interactions.Comment: 5 pages, 3 figures, 4 tables. Updated references. Cosmetic changes to figures, tables, and equations; added a sentence clarifying the correspondence between our real-space cutoffs and momentum-space cutoffs. Other sentences were reworded for clarit

    Signatures of few-body resonances in finite volume

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    We study systems of bosons and fermions in finite periodic boxes and show how the existence and properties of few-body resonances can be extracted from studying the volume dependence of the calculated energy spectra. Using a plane-wave-based discrete variable representation to conveniently implement periodic boundary conditions, we establish that avoided level crossings occur in the spectra of up to four particles and can be linked to the existence of multi-body resonances. To benchmark our method we use two-body calculations, where resonance properties can be determined with other methods, as well as a three-boson model interaction known to generate a three-boson resonance state. Finding good agreement for these cases, we then predict three-body and four-body resonances for models using a shifted Gaussian potential. Our results establish few-body finite-volume calculations as a new tool to study few-body resonances. In particular, the approach can be used to study few-neutron systems, where such states have been conjectured to exist.Comment: 13 pages, 10 figures, 2 tables, published versio

    Is a Trineutron Resonance Lower in Energy than a Tetraneutron Resonance?

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    We present quantum Monte Carlo calculations of few-neutron systems confined in external potentials based on local chiral interactions at next-to-next-to-leading order in chiral effective field theory. The energy and radial densities for these systems are calculated in different external Woods-Saxon potentials. We assume that their extrapolation to zero external-potential depth provides a quantitative estimate of three- and four-neutron resonances. The validity of this assumption is demonstrated by benchmarking with an exact diagonalization in the two-body case. We find that the extrapolated trineutron resonance, as well as the energy for shallow well depths, is lower than the tetraneutron resonance energy. This suggests that a three-neutron resonance exists below a four-neutron resonance in nature and is potentially measurable. To confirm that the relative ordering of three- and four-neutron resonances is not an artifact of the external confinement, we test that the odd-even staggering in the helium isotopic chain is reproduced within this approach. Finally, we discuss similarities between our results and ultracold Fermi gases.Comment: 6 pages, 5 figures, version compatible with published lette

    Chiral Three-Nucleon Interactions in Light Nuclei, Neutron-α\alpha Scattering, and Neutron Matter

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    We present quantum Monte Carlo calculations of light nuclei, neutron-α\alpha scattering, and neutron matter using local two- and three-nucleon (3N3N) interactions derived from chiral effective field theory up to next-to-next-to-leading order (N2^2LO). The two undetermined 3N3N low-energy couplings are fit to the 4^4He binding energy and, for the first time, to the spin-orbit splitting in the neutron-α\alpha PP-wave phase shifts. Furthermore, we investigate different choices of local 3N3N-operator structures and find that chiral interactions at N2^2LO are able to simultaneously reproduce the properties of A=3,4,5A=3,4,5 systems and of neutron matter, in contrast to commonly used phenomenological 3N3N interactions.Comment: 5 pages, 3 figures, 1 table - updated version: small wording changes, one reference chang
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