87,712 research outputs found
κ -Poincaré comodules, braided tensor products, and noncommutative quantum field theory
No full textWe discuss the obstruction to the construction of a multiparticle field theory on a κ-Minkowski noncommutative spacetime: the existence of multilocal functions which respect the deformed symmetries of the problem. This construction is only possible for a lightlike version of the commutation relations, if one requires invariance of the tensor product algebra under the coaction of the κ-Poincaré group. This necessitates a braided tensor product. We study the representations of this product, and prove that κ-Poincaré-invariant N-point functions belong to an Abelian subalgebra, and are therefore commutative. We use this construction to define the 2-point Whightman and Pauli-Jordan functions, which turn out to be identical to the undeformed ones. We finally outline how to construct a free scalar κ-Poincaré-invariant quantum field theory, and identify some open problems
Relative locality in κ-Poincaré
No full textWe show that the κ-Poincaré Hopf algebra can be interpreted in the framework of curved momentum space leading to relative locality. We study the geometric properties of the momentum space described by κ- Poincaré and derive the consequences for particle propagation and energy-momentum conservation laws in interaction vertices, obtaining for the first time a coherent and fully workable model of the deformed relativistic kinematics implied by κ-Poincaré. We describe the action of boost transformations on multi-particle systems, showing that the covariance of the composed momenta requires a dependence of the rapidity parameter on the particle momenta themselves. Finally, we show that this particular form of the boost transformations keeps the validity of the relativity principle, demonstrating the invariance of the equations of motion under boost transformations. © 2013 IOP Publishing Ltd
The momentum spaces of κ-Minkowski noncommutative spacetime
No full textA useful concept in the development of physical models on the κ-Minkowski noncommutative spacetime is that of a curved momentum space. This structure is not unique: several inequivalent momentum space geometries have been identified. Some are associated to a different assumption regarding the signature of spacetime (i.e. Lorentzian vs. Euclidean), but there are inequivalent momentum spaces that can be associated to the same signature and even the same group of symmetries. Moreover, in the literature there are two approaches to the definition of these momentum spaces, one based on the right- (or left-)invariant metrics on the Lie group generated by the κ-Minkowski algebra. The other is based on the construction of 5-dimensional matrix representation of the κ-Minkowski coordinate algebra. Neither approach leads to a unique construction. Here, we find the relation between these two approaches and introduce a unified approach, capable of describing all momentum spaces, and identify the corresponding quantum group of spacetime symmetries. We reproduce known results and get a few new ones. In particular, we describe the three momentum spaces associated to the κ-Poincaré group, which are half of a de Sitter, anti-de Sitter or Minkowski space, and we identify what distinguishes them. Moreover, we find a new momentum space with the geometry of a light cone, associated to a κ-deformation of the Carroll group
INNOVAZIONE TECNOLOGICA E REGOLAZIONE NELL’UNIONE EUROPEA. I MERCATI DELL’ALGORITMO TRA CONCORRENZA E PROTEZIONE DEI DATI
No full textIl saggio indaga il recente mutamento dell'approccio dell'Unione europea nella regolazione dei mercati, che supera la classica 'matrice regolatoria' e individua nuove forme e strumenti di intervento più coerenti con l'innovazione tecnologica. L'indagine approfondisce i temi della concorrenza e della tutela dei dati personali, in cui l'inefficacia della regolazione tradizionale rispetto all'innovazione tecnologica è paradigmatica
Localizability in κ -Minkowski spacetime
No full textUsing the methods of ordinary quantum mechanics, we study κ-Minkowski space as a quantum space described by noncommuting self-adjoint operators, following and enlarging T. Poulain and J.-C. Wallet, "κ-Poincaré invariant orientable field theories with at 1-loop: Scale-invariant couplings, preprint (2018), arXiv:1808.00350 [hep-th]. We see how the role of Fourier transforms is played in this case by Mellin transforms. We briefly discuss the role of transformations and observers
Banche e Mercati Finanziari
No full textIl volume contiene un'analisi dettagliata della normative europea in materia di banche, vigilanza prudenziale, crisi bancarie e tutela dei depositanti, conglomerati finanziari e credito al consumo, nonchè di quella relativa ai mercati mobiliari e agli intermediari finanziar
Istituzioni e mercati finanziari
No full textIl volume tratta la struttura e il funzionamento del sistema finanziario nell'economia. Le parti principali riguardano i mercati finanziari, gli strumenti finanziari e le istituzioni finanziarie.
A queste, si aggiungono due parti su banca centrale e funzione dei tassi di interesse nell'economia. Il contributo dell'autore ha riguardato in particolare le parti relative: 1) alla banca centrale e alla politica monetaria, 2) ai mercati e alle istituzioni finanziarie relativamente alle specificità del contesto europeo e italiano
Quantum gravity corrections to quantum field theory: Born-Oppenheimer approach to the canonical formalism
No full textThe role of time is intrinsically different between Quantum Mechanics and General Relativity: while the former associates time with an external observer, the latter unifies time and space, making them indistinguishable in a covariant framework. The absence of a clear time variable in GR stems from its symmetry and parametrized nature, resulting in the so-called frozen formalism.
For this reason, the search for a theory of Quantum Gravity must face the challenge of time absence in the Wheeler-de Witt equation.
Efforts to quantize gravity have led to various approaches to define time, categorized into pre-quantization, post-quantization, and timeless proposals. This thesis focuses on post-quantization time constructions, particularly within the Wentzel-Kramers-Brillouin approach, which perturbatively expands the wave function to derive dynamical equations. Previous attempts have shown that the introduction of an internal clock from gravitational variables yields non-unitary dynamical effects on the matter sector at the next order.
This thesis implements a Born-Oppenheimer-like scheme that separates the matter and gravitational sectors, leveraging their distinct energy scales: the matter's faster evolution is contrasted with the slower gravitational field, both properly quantum.
Two novel time constructions are proposed, making use of a fast component derived from introducing the kinematical action or (reparametrized) Gaussian frame fixing respectively; the discussion of their geometrical and physical meaning proves that both are essentially tied to the concept of a reference system.
These clocks for the matter subsystem overcome previous non-unitarity concerns, resulting in an Hermitian dynamics at the first order where quantum-gravitational corrections emerge. A direct equivalence between the two implementations is proved in the homogeneous minisuperspace setting.
The present investigation also faces the challenge posed by the dependence of the matter wave functional on intrinsically quantum gravitational components, particularly evident in the cosmological context. To address this, a more rigorous Born-Oppenheimer separation of dynamics is proposed, distinguishing the classical gravitational background from its small quantum fluctuations (i.e. gravitons) and then proper quantum matter contributions. By introducing an appropriate gauge choice for the gravitons' sector, the zero-th order of this model allows to recover the standard Quantum Field Theory dynamics.
We show how this refined scheme can be combined with the concept of a reference fluid time (or equivalently the kinematical action one), offering a unitary evolution for the quantum matter subsystem with quantum gravity corrections, free of previously mentioned concerns.
Such unified approach clarifies the quantum nature of gravitational components and shows how gauge requirements address the emergence of quantum gravity effects in subsequent orders of the expansion.
The central achievement of the present thesis is the development of a suitable Born-Oppenheimer scheme for the quantum gravity-matter system, in which the matter's evolution modified by quantum gravitational effects has a unitary character. This framework offers insights into how quantum gravity influences our understanding of the universe and contributes to a deeper comprehension of gravitational phenomena
The World of Adipokines: Their Presence and Distribution in the Organism and Their Relevance in Veterinary Medicine
No full textThe word “adipokines” generally identifies all the molecules synthesized and secreted by the adipose tissue. This evidence suggests that the adipose tissue can be no longer seen only as a storage tissue but also as a real “endocrine organ”. The adipokines carry out a local action (autocrine/paracrine) on the same producing tissue but also a systemic one (endocrine) on different target organs and tissues. The numerous studies conducted in this regard and the evidence of their distribution, often ubiquitous, with the presence of production sites additional to the adipose tissue, have allowed us to hypothesize and, in some cases, to demonstrate their involvement in the functional control of the organs where they have been highlighted.
Original manuscripts, review articles, and short communications and commentaries, which address any aspects of adipokines in domestic and wild animals, are invited for this special issue. Manuscripts that use a multidisciplinary approach and address any aspect of adipokines with a direct impact on animal welfare are particularly welcome
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