Search results for "Physical system"
showing 10 items of 113 documents
Geometric phase in open systems.
2003
We calculate the geometric phase associated to the evolution of a system subjected to decoherence through a quantum-jump approach. The method is general and can be applied to many different physical systems. As examples, two main source of decoherence are considered: dephasing and spontaneous decay. We show that the geometric phase is completely insensitive to the former, i.e. it is independent of the number of jumps determined by the dephasing operator.
A Graph-Theoretical Approach to Calculate Vibrational Energies of Atomic and Subatomic Systems
2012
One of the challenges still pending in string theory and other particle physics related fields is the accurate prediction of the masses of the elementary particles defined in the standard model. In this paper an original algorithm to assign graphs to each of these particles is proposed. Based on this mapping, we demonstrate that certain indices associated with the topology of the graph (graph theoretical indices) are very effective in predicting the masses of the particles. Specifically, the spectral moments of the graph adjacency matrix weighted by edge degrees play a key role in the excellent correlations found. Moreover, the same topological pattern is found in other well known quantum s…
Magnetic Stochastic Resonance in systems described by Dynamic Preisach Model
2008
Stochastic resonance (SR) is generally considered as an enhancement of the system response for certain finite values of the noise strength. In particular the signal to noise ratio (SNR) and the signal amplification show a maximum as a function of the noise intensity. This effect has been experimentally observed in many physical systems and also in magnetic systems. However, as far as magnetic systems are concerned, the dynamic features of the systems have been neglected and it has been assumed that the typical relaxation time is negligible. However this is clearly a rough approximation. In order to clarify this relation, in this paper we numerically study magnetic stochastic resonance in se…
Prosthetic modelling and simulation
2020
Abstract Modelling of physical systems can be divided into two categories: physical and mathematical modelling. Physical modelling is a process in which we construct tangible scale models that look very much like the real system. In the past century, consider the animal models that have significantly influenced the development of disease treatment and artificial joints. However, scale models require a great deal of time and resources to develop and there are limits to what can be learned from them. Mathematical or behavioural modelling is a more abstract system used for studying a research question that does not necessarily lend itself to physical modelling. In these models, the system is s…
Towards a Secure DevOps Approach for Cyber-Physical Systems
2020
With the expansion of cyber-physical systems (CPSs) across critical and regulated industries, systems must be continuously updated to remain resilient. At the same time, they should be extremely secure and safe to operate and use. The DevOps approach caters to business demands of more speed and smartness in production, but it is extremely challenging to implement DevOps due to the complexity of critical CPSs and requirements from regulatory authorities. In this study, expert opinions from 33 European companies expose the gap in the current state of practice on DevOps-oriented continuous development and maintenance. The study contributes to research and practice by identifying a set of needs…
Hamiltonians Generated by Parseval Frames
2021
AbstractIt is known that self-adjoint Hamiltonians with purely discrete eigenvalues can be written as (infinite) linear combination of mutually orthogonal projectors with eigenvalues as coefficients of the expansion. The projectors are defined by the eigenvectors of the Hamiltonians. In some recent papers, this expansion has been extended to the case in which these eigenvectors form a Riesz basis or, more recently, a ${\mathcal{D}}$ D -quasi basis (Bagarello and Bellomonte in J. Phys. A 50:145203, 2017, Bagarello et al. in J. Math. Phys. 59:033506, 2018), rather than an orthonormal basis. Here we discuss what can be done when these sets are replaced by Parseval frames. This interest is moti…
Gibbs states, algebraic dynamics and generalized Riesz systems
2020
In PT-quantum mechanics the generator of the dynamics of a physical system is not necessarily a self-adjoint Hamiltonian. It is now clear that this choice does not prevent to get a unitary time evolution and a real spectrum of the Hamiltonian, even if, most of the times, one is forced to deal with biorthogonal sets rather than with on orthonormal basis of eigenvectors. In this paper we consider some extended versions of the Heisenberg algebraic dynamics and we relate this analysis to some generalized version of Gibbs states and to their related KMS-like conditions. We also discuss some preliminary aspects of the Tomita-Takesaki theory in our context.
Fractional Laplacians in bounded domains: Killed, reflected, censored, and taboo Lévy flights.
2018
The fractional Laplacian $(- \Delta)^{\alpha /2}$, $\alpha \in (0,2)$ has many equivalent (albeit formally different) realizations as a nonlocal generator of a family of $\alpha $-stable stochastic processes in $R^n$. On the other hand, if the process is to be restricted to a bounded domain, there are many inequivalent proposals for what a boundary-data respecting fractional Laplacian should actually be. This ambiguity holds true not only for each specific choice of the process behavior at the boundary (like e.g. absorbtion, reflection, conditioning or boundary taboos), but extends as well to its particular technical implementation (Dirchlet, Neumann, etc. problems). The inferred jump-type …
$O^\star$-algebras and quantum dynamics: some existence results
2008
We discuss the possibility of defining an algebraic dynamics within the settings of O -algebras. Compared to our previous results on this subject, the main improvement here is that we are not assuming the existence of some Hamiltonian for the full physical system. We will show that, under suitable conditions, the dynamics can still be defined via some limiting procedure starting from a given regularized sequence. © 2008 American Institute of Physics.
Unitary Transfer of Entanglement in Multipartite Two-Level Systems
2005
The dynamics of a system composed by two pairs of dipolarly coupled two-level atoms is exactly studied. We show that the initial entanglement stored in a couple of atoms not directly interacting is fully transferred to the other pair in a periodic way. The observability of this phenomenon in laboratory is briefly discussed both in terms of its temporal scale and of its stability against uncertainties in the geometrical parameters defining the physical system.