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Unitary state

About: Unitary state is a(n) research topic. Over the lifetime, 4651 publication(s) have been published within this topic receiving 72606 citation(s).
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Journal ArticleDOI
Abstract: Any finite group of linear transformations on n variables leaves invariant a positive definite Hermitian form, and can therefore be expressed, after a suitable change of variables, as a group of unitary transformations (5, p. 257). Such a group may be thought of as a group of congruent transformations, keeping the origin fixed, in a unitary space Un of n dimensions, in which the points are specified by complex vectors with n components, and the distance between two points is the norm of the difference between their corresponding vectors.

1,197 citations

Journal ArticleDOI

1,119 citations

Journal ArticleDOI
S. Okubo1Institutions (1)
15 Jun 1963-Physics Letters

697 citations

01 Jan 1997-
Abstract: Presents a theory of domestic politics, showing how it affects international outcomes. In developing this rational choice theory, the text argues that any explanation that treats states as unitary actors is misleading. It describes all states as polyarchic, where decision-making power is shared between two or more actors (such as legislature and executive). A model is constructed based on two-level game theory, reflecting the political activity at both the domestic and international levels. The model is illustrated by the question of co-operation between nations.

671 citations

Journal ArticleDOI
13 Jan 2011-Physical Review B
Abstract: Quantum many-body systems divide into a variety of phases with very different physical properties. The questions of what kinds of phases exist and how to identify them seem hard, especially for strongly interacting systems. Here we make an attempt to answer these questions for gapped interacting quantum spin systems whose ground states are short-range correlated. Based on the local unitary equivalence relation between short-range-correlated states in the same phase, we classify possible quantum phases for one-dimensional (1D) matrix product states, which represent well the class of 1D gapped ground states. We find that in the absence of any symmetry all states are equivalent to trivial product states, which means that there is no topological order in 1D. However, if a certain symmetry is required, many phases exist with different symmetry-protected topological orders. The symmetric local unitary equivalence relation also allows us to obtain some simple results for quantum phases in higher dimensions when some symmetries are present.

607 citations

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Topic's top 5 most impactful authors

Shao-Ming Fei

38 papers, 228 citations

Kh. D. Ikramov

14 papers, 22 citations

Scott N. Walck

12 papers, 81 citations

David W. Lyons

12 papers, 83 citations

Yoshifumi Nakata

8 papers, 102 citations