Simulating Hamiltonian dynamics using many-qudit Hamiltonians and local unitary control

When can a quantum system of finite dimension be used to simulate another quantum system of finite dimension? What restricts the capacity of one system to simulate another? In this paper we complete the program of studying what simulations can be done with entangling many-qudit Hamiltonians and local unitary control. By entangling we mean that every qudit is coupled to every other qudit, at least indirectly. We demonstrate that the only class of finite-dimensional entangling Hamiltonians that aren't universal for simulation is the class of entangling Hamiltonians on qubits whose Pauli operator expansion contains only terms coupling an odd number of systems, as identified by Bremner et. al. [Phys. Rev. A, 69, 012313 (2004)]. We show that in all other cases entangling many-qudit Hamiltonians are universal for simulation

Beyond Metaphysics:Gianni Vattimo and the meaning of hermeneutics for political theory

This article examines Gianni Vattimo’s contribution to the recent ontological turn in political theory. Drawing on Nietzsche and Heidegger, Vattimo offers a ‘philosophy of history’ in which strong metaphysical claims are presented as gradually being weakened, but in which the irrationalism he thinks characteristic of many anti-foundationalist theorists is also avoided. This philosophy is said to provide for new understandings of ethical and political life which have the acceptance of pluralism as their aim. The article argues that Vattimo’s attempt to identify a position beyond metaphysics on the one hand and relativism on the other is unsuccessful, and that he ought to join in with the thoroughgoing anti-foundationalism that marks the work of writers such as Rorty and Derrida. It suggests further that awareness of our historical situation need not weaken the confidence with which our beliefs are held, and does not support any particular political programme. </jats:p

Applications of PB-210/RA-226 and PO-210/PB-210 disequilibria in the study of marine geochemical processes

Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution November, 1975The distribution of Pb-210 and Po-210 in dissolved (0.4 micron) phases has been measured at ten stations in the tropical and eastern North Atlantic and at two stations in the Pacific. Both radionuclides occur principally in the dissolved phase. Unsupported Pb-210 activities, maintained by flux from the atmosphere, are present in the surface mixed layer and penetrate into the thermocline to depths of about 500 m. Dissolved Po-210 is ordinarily present in the mixed layer at less than equilibrium concentrations, suggesting rapid biological removal of this nuclide. Particulate matter is enriched in Po-210, with Po-210/Pb-210 activity ratios greater than 1.0, similar to those reported for phytoplankton. Box-model calculations yield a 2-y residence time for Pb-210 and a 0.6-y residence time for Po-210 in the mixed layer. These residence times are considerably longer than the time calculated for turnover of particles in the mixed layer (about 0.1 y). At depths of 100-300 m, Po-210 maxima occur and unsupported Po-210 is frequently present. Calculations indicate that at least 50% of the Po-210 removed from the mixed layer is recycled within the thermocline. Similar calculations for Pb-210 suggest much lower recycling efficiencies. Comparison of the Pb-210 distribution with the reported distribution of Ra-226 at nearby GEOSECS. stations has confirmed the widespread existence of a Pb-210/Ra-226 disequilibrium in the deep sea. Vertical profiles of particulate Pb-210 were used to test the hypothesis that Pb-210 is removed from deepwater by in situ scavenging. With the exception of one profile taken near the Mid-Atlantic Ridge, significant vertical gradients in particulate Pb-210 concentration were not observed, and it is necessary to invoke exceptionally high particle sinking velocities (>10 m/d) to account for the inferred Pb-210 flux. It is proposed that an additional sink for Pb-210 in the deep sea must be sought. Estimates of the dissolved Pb-210/Ra-226 activity ratio at depths greater than 1,000 m range from 0.2 to 0.8 and reveal a systematic increase, in both vertical and horizontal directions, with increasing distance from the sea floor. This observation implies rapid scavenging of Pb-210 at the sediment-water interface and is consistent with a horizontal eddy diffusivity of 3-6 x 107 cm2/s. The more reactive element Po, on the other hand, shows evidence of rapid in situ scavenging. In filtered sea water, Po-210 is deficient, on the average, by ca. 10% relative to Pb-210; a corresponding enrichment is found in the particulate phase. Total inventories of Pb-210 and Po-210 over the entire water column, however, show no significant departure from secular equilibrium, and reliable estimates of particle sinking rates cannot be made.Prepared under National Science Foundation Grant GA-41061 and U.S.A.E.C. Contract AT(11-1)

Deconstructing the ivory tower: identifying challenges of university-industry ecosystem partnerships

Collaboration between industry and academia necessitates the management of entrepreneurial dynamics within ecosystem contexts. However, such partnerships perpetuate numerous challenges that, without effective management, can impact upon the ecosystem as a whole. Limited research to date has addressed the challenges affecting these university-industry partnerships and ascertained their impact upon ecosystem management. This study identifies the challenges pervading university-industry partnerships across entrepreneurial ecosystems, with a view that through an exposition of such challenges, more specific strategies could be implemented to address them. Questionnaires were distributed to key ecosystem stakeholders, requesting their perceptions of the key challenges affecting their collaborative relationships. Empirical data was analysed utilising fuzzy-set qualitative comparative analysis to deduce the configurational nature of the conditions. Results reveal mutually exclusive solutions grounded upon distinct combinations of conditions, constituting distinct pathways to ineffective ecosystem management. Theoretical and practical implications are discussed, as well as acknowledged limitations of this study and suggestions for future research

Coarse embeddings of graphs into Hilbert space

In this paper, we study coarse embeddings of graphs into Hilbert space. For a graph &Gamma expressible as an infinite union of coarsely embeddable subgraphs, &Gammai, we prove that if the nerve of the covering of &Gamma by the &Gammai is a tree and any nonempty intersections of the subgraphs have universally bounded diameter then &Gamma is coarsely embeddable into a Hilbert space