20,965 research outputs found
A Potentiality and Conceptuality Interpretation of Quantum Physics
We elaborate on a new interpretation of quantum mechanics which we introduced
recently. The main hypothesis of this new interpretation is that quantum
particles are entities interacting with matter conceptually, which means that
pieces of matter function as interfaces for the conceptual content carried by
the quantum particles. We explain how our interpretation was inspired by our
earlier analysis of non-locality as non-spatiality and a specific
interpretation of quantum potentiality, which we illustrate by means of the
example of two interconnected vessels of water. We show by means of this
example that philosophical realism is not in contradiction with the recent
findings with respect to Leggett's inequalities and their violations. We
explain our recent work on using the quantum formalism to model human concepts
and their combinations and how this has given rise to the foundational ideas of
our new quantum interpretation. We analyze the equivalence of meaning in the
realm of human concepts and coherence in the realm of quantum particles, and
how the duality of abstract and concrete leads naturally to a Heisenberg
uncertainty relation. We illustrate the role played by interference and
entanglement and show how the new interpretation explains the problems related
to identity and individuality in quantum mechanics. We put forward a possible
scenario for the emergence of the reality of macroscopic objects.Comment: 20 pages, 1 figur
Dynamic quantum clustering: a method for visual exploration of structures in data
A given set of data-points in some feature space may be associated with a
Schrodinger equation whose potential is determined by the data. This is known
to lead to good clustering solutions. Here we extend this approach into a
full-fledged dynamical scheme using a time-dependent Schrodinger equation.
Moreover, we approximate this Hamiltonian formalism by a truncated calculation
within a set of Gaussian wave functions (coherent states) centered around the
original points. This allows for analytic evaluation of the time evolution of
all such states, opening up the possibility of exploration of relationships
among data-points through observation of varying dynamical-distances among
points and convergence of points into clusters. This formalism may be further
supplemented by preprocessing, such as dimensional reduction through singular
value decomposition or feature filtering.Comment: 15 pages, 9 figure
Cluster states in nuclei as representations of a U(n+1) group
We propose a description of cluster states in nuclei in terms of
representations of unitary algebras U(n+1), where n is the number of space
degrees of freedom. Within this framework, a variety of situations including
both vibrational and rotational spectra, soft and rigid configurations,
identical and non-identical constituents can be described. As an example, we
show how the method can be used to study alpha-clustering configurations in 12C
with point group symmetry D(3h).Comment: 5 pages, 2 figures, Phys. Rev. C, in pres
High posterior density ellipsoids of quantum states
Regions of quantum states generalize the classical notion of error bars. High
posterior density (HPD) credible regions are the most powerful of region
estimators. However, they are intractably hard to construct in general. This
paper reports on a numerical approximation to HPD regions for the purpose of
testing a much more computationally and conceptually convenient class of
regions: posterior covariance ellipsoids (PCEs). The PCEs are defined via the
covariance matrix of the posterior probability distribution of states. Here it
is shown that PCEs are near optimal for the example of Pauli measurements on
multiple qubits. Moreover, the algorithm is capable of producing accurate PCE
regions even when there is uncertainty in the model.Comment: TL;DR version: computationally feasible region estimator
A Wave-Mechanical Approach to Cosmic Structure Formation
The dynamical equations describing the evolution of a self-gravitating fluid
can be rewritten in the form of a Schrodinger equation coupled to a Poisson
equation determining the gravitational potential. This wave-mechanical
representation allows an approach to cosmological gravitational instability
that has numerous advantages over standard fluid-based methods. We explore the
usefulness of the Schrodinger approach by applying it to a number of simple
examples of self-gravitating systems in the weakly non-linear regime. We show
that consistent description of a cold self-gravitating fluid requires an extra
"quantum pressure" term to be added to the usual Schrodinger equation and we
give examples of the effect of this term on the development of gravitational
instability. We also show how the simple wave equation can be modified by the
addition of a non-linear term to incorporate the effects of gas pressure
described by a polytropic equation-of-state.Comment: 9 pages, 2 figures. Minor changes. Accepted for publication in MNRA
On the symmetry of the vacuum in theories with spontaneous symmetry breaking
We review the usual account of the phenomena of spontaneous symmetry breaking
(SSB), pointing out the common misunderstandings surrounding the issue, in
particular within the context of quantum field theory. In fact, the common
explanations one finds in this context, indicate that under certain conditions
corresponding to the situation called SSB, the vacuum of the theory does not
share the symmetries of the Lagrangian. We explain in detail why this statement
is incorrect in general, and in what limited set of circumstances such
situation could arise. We concentrate on the case of global symmetries, for
which we found no satisfactory exposition in the existing literature, and
briefly comment on the case of gauge symmetries where, although insufficiently
publicized, accurate and complete descriptions exist. We briefly discuss the
implications for the phenomenological manifestations usually attributed to the
phenomena of spontaneous symmetry breaking, analyzing which might be affected
by our analysis and which are not. In particular we describe the mass
generation mechanism in a fully symmetric scheme (i.e., with a totally
symmetric vacuum), and briefly discuss the implications of this analysis to the
problem of formation of topological defects in the early universe
Structure and singly occupied molecular orbital analysis of anionic tautomers of guanine
Recently we reported the discovery of adiabatically bound anions of guanine which might be involved in the processes of DNA damage by low-energy electrons and in charge transfer through DNA. These anions correspond to some tautomers that have been ignored thus far. They were identified using a hybrid quantum mechanical-combinatorial approach in which an energy-based screening was performed on the library of 499 tautomers with their relative energies calculated with quantum chemistry methods.
In the current study we analyze the adiabatically bound anions of guanine in two aspects: 1) the geometries and excess electron distributions are analyzed and compared with anions of the most stable neutrals to identify the sources of stability; 2)
the chemical space of guanine tautomers is explored to verify if these new tautomers are contained in a particular subspace of the tautomeric space. The first task involves the development of novel approaches – the quantum chemical data like electron density, orbital and information on its bonding/antibonding character are coded into holograms and analyzed using chemoinformatics techniques. The second task is completed using substructure analysis and clustering techniques performed on molecules represented by 2D fingerprints.
The major conclusion is that the high stability of adiabatically bound anions originates from the bonding character of the pi orbital occupied by the excess electron. This compensates for the antibonding character that usually causes significant buckling of the ring. Also the excess electron is more homogenously distributed over both rings than in the case of anions of the most stable neutral species. In terms of 2D substructure, the most stable anionic tautomers generally have additional hydrogen atoms at C8 and/or C2 and they don’t have hydrogen atoms attached to C4, C5 and C6. They also form an “island of stability” in the tautomeric space of guanine
Bifurcation in Rotational Spectra of Nonlinear AB Molecules
A classical microscopic theory of rovibrational motion at high angular
momenta in symmetrical non-linear molecules AB is derived within the
framework of small oscillations near the stationary states of a rotating
molecule. The full-dimensional analysis including stretching vibrations has
confirmed the existence of the bifurcation predicted previously by means of the
rigid-bender model. The formation of fourfold energy clusters has already been
experimentally verified for HSe and it has been demonstrated in
fully-dimensional quantum mechanical calculations using the MORBID computer
program. We show in the present work that apart from the level clustering, the
bifurcation produces physically important effects including molecular
symmetry-breaking and a transition from the normal mode to the local mode limit
for the stretching vibrations due to rovibrational interaction. The application
of the present theory with realistic molecular potentials to the HTe,
HSe and HS hydrides results in predictions of the bifurcation points
very close to those calculated previously. However for the lighter HO
molecule we find that the bifurcation occurs at higher values of the total
angular momentum than obtained in previous estimations. The present work shows
it to be very unlikely that the bifurcation in HO will lead to clustering
of energy levels. This result is in agreement with recent variational
calculations.Comment: latex, 19 pages including 2 figures provided as *.uu fil
Community Detection in Quantum Complex Networks
Determining community structure is a central topic in the study of complex
networks, be it technological, social, biological or chemical, in static or
interacting systems. In this paper, we extend the concept of community
detection from classical to quantum systems---a crucial missing component of a
theory of complex networks based on quantum mechanics. We demonstrate that
certain quantum mechanical effects cannot be captured using current classical
complex network tools and provide new methods that overcome these problems. Our
approaches are based on defining closeness measures between nodes, and then
maximizing modularity with hierarchical clustering. Our closeness functions are
based on quantum transport probability and state fidelity, two important
quantities in quantum information theory. To illustrate the effectiveness of
our approach in detecting community structure in quantum systems, we provide
several examples, including a naturally occurring light-harvesting complex,
LHCII. The prediction of our simplest algorithm, semiclassical in nature,
mostly agrees with a proposed partitioning for the LHCII found in quantum
chemistry literature, whereas our fully quantum treatment of the problem
uncovers a new, consistent, and appropriately quantum community structure.Comment: 16 pages, 4 figures, 1 tabl
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