1,721,108 research outputs found
κ -Poincaré comodules, braided tensor products, and noncommutative quantum field theory
Full text linkWe 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
Discreteness of area in noncommutative space
No full textWe introduce an area operator for the Moyal noncommutative plane. We find that the spectrum is discrete, but, contrary to the expectation formulated by other authors, not characterized by a "minimum-area principle". We show that an intuitive analysis of the uncertainty relations obtained from Moyal-plane noncommutativity is fully consistent with our results for the spectrum, and we argue that our area operator should be generalizable to several other noncommutative spaces. We also observe that the properties of distances and areas in the Moyal plane expose some weaknesses in the line of reasoning adopted in some of the heuristic analyses of the measurability of geometric spacetime observables in the quantum-gravity realm. © 2009 Elsevier B.V. All rights reserved
Interplay between spacetime curvature, speed of light and quantum deformations of relativistic symmetries
No full textRecent work showed that κ-deformations can describe the quantum deformation of several relativistic models that have been proposed in the context of quantum gravity phenomenology. Starting from the Poincaré algebra of special-relativistic symmetries, one can toggle the curvature parameter Λ, the Planck scale quantum deformation parameter κ and the speed of light parameter c to move to the well-studied κ-Poincaré algebra, the (quantum) (A)dS algebra, the (quantum) Galilei and Carroll algebras and their curved versions. In this review, we survey the properties and relations of these algebras of relativistic symmetries and their associated noncommutative spacetimes, emphasizing the nontrivial effects of interplay between curvature, quantum deformation and speed of light parameters
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
Cythomorphological evaluation of horse adipose-derived mesenchymal stem cells after different storage conditions
No full textTransplantation of mesenchymal stem cells (MSCs) is a promising therapy and it
is known that, in the horse, these cells are already used for teno-desmic injuries treatment.
However, till now, knowledge about the MSC behaviour is scarce (Koch, Can.
Vet.J., 50, 2009) and, in particular, data on the effects of the cell manipulation before
transplantation are lacking.
In this work we studied MSCs maintained at different temperatures for different
periods of time simulating the phase of conservation before their use. Cryopreserved
MSCs were thawed, resuspended in a medium devoid of fetal calf serum (1x106cc/ml)
and divided in five aliquots. After a maintenance at 4°C or at room temperature for
0, 24 and 48 hours, MSCs were used for the following trials: cell viability, duplication
time, Colony-Forming Unit Assays, karyotype evaluation, adipogenic and osteogenic
differentiation, expression of MSC marker CD44 and CD90. Result evaluation seems to
suggest that all tested manipulation were unable to induce appreciable modifications
on MSC behaviour. All the aliquots were clonogenic, could differentiate along the osteogenic
and adipogenic lineage and expressed high levels of CD44 and CD90 antigens.
We suppose that the tested conditions of maintenance do not change the characteristics
of horse adipose-derived MSCs as regards the considered parameters
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