Density matrix embedding: A strong-coupling quantum embedding theory

We extend our density matrix embedding theory (DMET) [Phys. Rev. Lett. 109 186404 (2012)] from lattice models to the full chemical Hamiltonian. DMET allows the many-body embedding of arbitrary fragments of a quantum system, even when such fragments are open systems and strongly coupled to their environment (e.g., by covalent bonds). In DMET, empirical approaches to strong coupling, such as link atoms or boundary regions, are replaced by a small, rigorous quantum bath designed to reproduce the entanglement between a fragment and its environment. We describe the theory and demonstrate its feasibility in strongly correlated hydrogen ring and grid models; these are not only beyond the scope of traditional embeddings, but even challenge conventional quantum chemistry methods themselves. We find that DMET correctly describes the notoriously difficult symmetric dissociation of a 4x3 hydrogen atom grid, even when the treated fragments are as small as single hydrogen atoms. We expect that DMET will open up new ways of treating of complex strongly coupled, strongly correlated systems in terms of their individual fragments.Comment: 5 pages, 4 figure

The Research University in Today's Society

In this topical lecture, investor and philanthropist Gerald Chan examines the role of philanthropy in the rapidly changing higher education environment. He proposes that society will be short-changed if the purpose of universities is seen as human resource rather than humanity. Dr Chan argues that the independence of universities is crucial for maintaining the balance between their dual role as engines of the economy and places of curiosity-driven research, and that a philanthropic public private partnership is vital to that. ‘Higher education is not cheap; but what is more expensive to society are the consequences of not supporting its universities… In a democratic society, governments come and go, and government funding priorities come and go, but a properly managed endowment endures.’ Dr Chan’s thought-provoking lecture ranges from pre-Enlightenment beliefs to the invention by Steve Jobs of the first Apple Macs, to demonstrate the vital role of universities to humanity

International studies in Taiwan today : a preliminary survey of the problems and prospects

International relations, as an academic study, is relatively new. It is much more developed, discussed and documented in the West, especially the US, than in other places. Within Asia, reports about international relations have begun to appear in Japan and China. This working paper is the first of its kind specifically to examine and make a survey of the study of international relations in Taiwan. The paper begins by giving an historical background, and then discusses the academic study of political science, both at the undergraduate and postgraduate levels in universities. Particular attention is paid to the activities of the Institute of International Relations, the leading institution in the country with a research focus on international relations and Chinese affairs. It ends by analysing the problems of and prospects for studying international relations in Taiwan. This analysis is placed within the context of Taiwan’s unique position in the world, its acrimonious relationship with China, its speedy process of democratisation and the recognised need among the country’s elite for a better understanding of international affairs. On the whole the study of international relations in Taiwan is distinctively policyoriented, with a specific focus on the country's relations with China and the United States, and with little theoretical interest. However, Taiwan's unique experience in world affairs offers a fertile ground for theoretical development which may contribute to an enrichment of the existing international relations scholarship

The intermediate and spin-liquid phase of the half-filled honeycomb Hubbard model

We obtain the phase-diagram of the half-filled honeycomb Hubbard model with density matrix embedding theory, to address recent controversy at intermediate couplings. We use clusters from 2-12 sites and lattices at the thermodynamic limit. We identify a paramagnetic insulating state, with possible hexagonal cluster order, competitive with the antiferromagnetic phase at intermediate coupling. However, its stability is strongly cluster and lattice size dependent, explaining controver- sies in earlier work. Our results support the paramagnetic insulator as being a metastable, rather than a true, intermediate phase, in the thermodynamic limit

Automated construction of molecular active spaces from atomic valence orbitals

We introduce the atomic valence active space (AVAS), a simple and well-defined automated technique for constructing active orbital spaces for use in multiconfiguration and multireference (MR) electronic structure calculations. Concretely, the technique constructs active molecular orbitals capable of describing all relevant electronic configurations emerging from a targeted set of atomic valence orbitals (e.g., the metal d orbitals in a coordination complex). This is achieved via a linear transformation of the occupied and unoccupied orbital spaces from an easily obtainable single-reference wave function (such as from a Hartree–Fock or Kohn–Sham calculations) based on projectors to targeted atomic valence orbitals. We discuss the premises, theory, and implementation of the idea, and several of its variations are tested. To investigate the performance and accuracy, we calculate the excitation energies for various transition-metal complexes in typical application scenarios. Additionally, we follow the homolytic bond breaking process of a Fenton reaction along its reaction coordinate. While the described AVAS technique is not a universal solution to the active space problem, its premises are fulfilled in many application scenarios of transition-metal chemistry and bond dissociation processes. In these cases the technique makes MR calculations easier to execute, easier to reproduce by any user, and simplifies the determination of the appropriate size of the active space required for accurate results

Transparency Confined to the Courthouse: A Critical Analysis of Criminal Lawyer\u27s Assn., C.B.C. and National Post

The Supreme Court of Canada constitutionalized the open court principle under section 2(b) of the Canadian Charter of Rights and Freedoms in its groundbreaking ruling in Edmonton Journal (1989). The Court’s holding was premised on three propositions: (1) the courts play an important role in our democratic society; (2) freedom of expression protects listeners as well as speakers; and (3) most individuals are dependent on the press to learn of what is transpiring in the courts. Taken together, these propositions suggested a broad conception of section 2(b) that could act as the primary guarantor of transparency in our democracy, not just within the courthouse but beyond. In 2010, however, the Supreme Court decided three cases that together rejected this vision. This paper reviews these three decisions and examines the manner in which they reined in the robust conception of section 2(b) that once seemed within reach

Remedial Minimalism under Section 24(1) of the Charter: Bjelland, Khadr and Nasogaluak

Three recent judgments of the Supreme Court of Canada signal a departure from the broad and generous manner in which the Court has previously interpreted and applied section 24(1) of the Charter. In each of R. v. Bjelland, Canada (Prime Minister) v. Khadr and R. v. Nasogaluak, the Supreme Court agreed with the trial judge’s finding of a breach of Charter rights but overturned the trial judge’s choice of remedy under section 24(1) in order to grant a more limited remedy in its place. In doing so, the Court shifted the analytical focus away from the promotion of remedial efficacy and toward the minimization of the burdens imposed by the remedy on government. This article reviews each of these judgments and examines the extent to which they are consistent with previous section 24(1) jurisprudence and the purpose of the Charter’s broadest remedial provision

Remedial Minimalism under Section 24(1) of the Charter: Bjelland, Khadr and Nasogaluak

Three recent judgments of the Supreme Court of Canada signal a departure from the broad and generous manner in which the Court has previously interpreted and applied section 24(1) of the Charter. In each of R. v. Bjelland, Canada (Prime Minister) v. Khadr and R. v. Nasogaluak, the Supreme Court agreed with the trial judge’s finding of a breach of Charter rights but overturned the trial judge’s choice of remedy under section 24(1) in order to grant a more limited remedy in its place. In doing so, the Court shifted the analytical focus away from the promotion of remedial efficacy and toward the minimization of the burdens imposed by the remedy on government. This article reviews each of these judgments and examines the extent to which they are consistent with previous section 24(1) jurisprudence and the purpose of the Charter’s broadest remedial provision

Text Message Privacy: Who Else Is Reading This?

Who talks on the phone anymore? Many of us perhaps. But we do so far less than we did 10 to 15 years ago. And we are increasingly relying on text conversations — whether through Short Message Service (“SMS”) messaging, e-mail or some other “app” — as our primary mode of communication. A 2014 Gallup poll found that Americans under the age of 50 text more than they talk on their cell phones. Canadians are unlikely to be much different, and the numbers have almost certainly moved further in the direction of texting over the last four years