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

Life after Vu: Manner of Computer Searches and Search Protocols

Computers have been an indispensable part of our lives for at least two decades. Given the extent of our dependency on computers and the vast amounts of information that they contain, it was inevitable that they would become the focal point of criminal investigations. The unique privacy concerns raised by computers create special challenges for search and seizure law under section 8 of the Charter. In recent years, the Supreme Court of Canada has decided several important cases dealing with the search and seizure of computers under section 8. Most recently, in R. v. Vu, the Court held that the police cannot search the contents of a computer upon executing a search warrant on the place in which the computer is found unless the warrant specifically authorizes the search of that computer. The Court also made some useful comments concerning the regulation of the manner of computer searches, including: (i) the manner of computer searches will generally be reviewed after the fact if and when a Charter challenge is brought; and (ii) in certain cases, it may be appropriate to impose search protocols (i.e., ex ante conditions spelled out in the warrant to limit the scope of the search). This paper seeks to build on the Court’s statements and imagine the post-Vu world of computer search and seizure law. The paper first summarizes Vu and the propositions for which it stands. It next takes up Vu’s invitation to carefully examine the manner of computer searches and draws on lower court decisions in an attempt to tease out some general principles to guide ex post review. It the n analyzes the issue of search protocols and when it might be appropriate — and, indeed, constitutionally required — for authorizing justices to impose such protocols before computer searches are conducted

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

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

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

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