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We develop some formalism which is very general Feynman path integral in the case of the action which is allowed to be complex. The major point is that the effect of the imaginary part of the action (mainly) is to determine which solution…

General Physics · Physics 2009-10-13 Holger B. Nielsen , Masaao Ninomiya

We review a work by M.Ninomiya and myself about a model for the initial state - i.e. which solution to the equations of motions - that is being realized. The to be realized solution is suggeted to be the one for which a certain number…

Popular Physics · Physics 2009-04-12 Holger B. Nielsen

We want to unify usual equation of motion laws of nature with "laws" about initial conditions, second law of thermodynamics, cosmology. By introducing an imaginary part -- of a similar form but different parameters as the usual real part --…

High Energy Physics - Phenomenology · Physics 2007-05-23 Holger B. Nielsen , Masao Ninomiya

In quantum theory its action is usually taken to be real, but we can consider another theory whose action is complex. In addition, in the Feynman path integral, the time integration is usually performed over the period between the initial…

Quantum Physics · Physics 2018-02-02 Keiichi Nagao , Holger Bech Nielsen

It is shown that the transactional interpretation of quantum mechanics being referred back to Feynman-Wheeler's time reversal symmetric radiation theory has reminiscences to our complex action model. In this complex action model the initial…

General Physics · Physics 2010-08-04 Holger B. Nielsen , Masao Ninomiya

This paper implements in a simple but rigorous fashion a model of particle interaction involving all paths within a quantum system, both for configuration space and for spin. The model, which we call the space of all paths, leads to a…

Quantum Physics · Physics 2011-06-15 Warren Leffler

We study a complex action theory (CAT) whose path runs over not only past but also future. We show that if we regard a matrix element defined in terms of the future state at time $T_B$ and the past state at time $T_A$ as an expectation…

Quantum Physics · Physics 2019-01-25 Keiichi Nagao , Holger Bech Nielsen

It is the purpose of the present article to collect arguments for, that there should exist in fact -- although not necessarily yet found -- some law, which imply an adjustment to special features to occur in the future. In our own "complex…

General Physics · Physics 2015-03-31 Holger Bech Nielsen

In a special representation of complex action theory that we call ``future-included'', we study a harmonic oscillator model defined with a non-normal Hamiltonian $\hat{H}$, in which a mass $m$ and an angular frequency $\omega$ are taken to…

Quantum Physics · Physics 2019-06-19 Keiichi Nagao , Holger Bech Nielsen

It was recently noted that the on-shell Einstein-Hilbert action with York-Gibbons-Hawking boundary term has an imaginary part, proportional to the area of the codimension-2 surfaces on which the boundary normal becomes null. We discuss the…

General Relativity and Quantum Cosmology · Physics 2013-09-13 Norbert Bodendorfer , Yasha Neiman

The present work contains a review of some of the work we have done on complex action or non-Hermitian Hamiltonian theory, especially the result that the anti-Hermitian part of the Hamiltonian functions by determining the actual solution to…

Quantum Physics · Physics 2023-03-09 Holger Bech Nielsen , Keiichi Nagao

Imaginary time is often used in quantum tunnelling calculations. This article advocates a conceptually sounder alternative: complex lapse. In the ``3+1'' action for the Einstein gravitational field minimally coupled to a Klein-Gordon field,…

General Relativity and Quantum Cosmology · Physics 2009-10-28 Sean A. Hayward

We introduce an original model of quantum phenomena, a model that provides a picture of a "deep structure", an "underlying pattern" of quantum dynamics. We propose that the source of a particle and all of that particle's possible detectors…

Quantum Physics · Physics 2007-05-23 Pavel Kurakin , George Malinetskii , Howard Bloom

If it is to be true that the history of the universe should be adjusted to minimize the "imaginary part of action" [arXiv:0802.2991, arXiv:0711.3080, arXiv:0707.1919, arXiv:hep-ph/0612032, arXiv:hep-th/0509205, arXiv:hep-th/0701018], it…

General Physics · Physics 2011-03-03 Holger Bech Nielsen

The theory of causal fermion systems is a recent approach to fundamental physics. Giving quantum mechanics, general relativity and quantum field theory as limiting cases, it is a candidate for a unified physical theory. The dynamics is…

Mathematical Physics · Physics 2019-09-25 Felix Finster

We consider two approaches to calculate imaginary parts of effective actions in expanding space-times. While the first approach uses Bogolyubov coefficients, the second one uses the functional integral or the Feynman propagator. In…

High Energy Physics - Theory · Physics 2025-12-22 E. T. Akhmedov , I. A. Belkovich , D. V. Diakonov , K. A. Kazarnovskii

In the future-included real action theory whose path runs over not only past but also future, we demonstrate a theorem, which states that the normalized matrix element of a Hermitian operator $\hat{\cal O}$ defined in terms of the future…

Quantum Physics · Physics 2017-08-04 Keiichi Nagao , Holger Bech Nielsen

In this paper, we survey recent progress on the constructive theory of the Feynman operator calculus. (The theory is constructive in that, operators acting at different times, actually commute.) We first develop an operator version of the…

Mathematical Physics · Physics 2011-01-27 Tepper L Gill , Woodford W Zachary

The capability of imagining internally with a mental model of the world is vitally important for human cognition. If a machine intelligent agent can learn a world model to create a "dream" environment, it can then internally ask what-if…

Machine Learning · Computer Science 2020-12-29 Minne Li , Mengyue Yang , Furui Liu , Xu Chen , Zhitang Chen , Jun Wang

It is first pointed out that there is a common mathematical model for the universe and the quantum computer. The former is called the histories approach to quantum mechanics and the latter is called measurement based quantum computation.…

Quantum Physics · Physics 2022-09-01 Stan Gudder
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