204 research outputs found
Rainbow metric formalism and Relative Locality
This proceeding is based on a talk prepared for the XIII Marcell Grossmann
meeting. We summarise some results of work in progress in collaboration with
Giovanni Amelino-Camelia about momentum dependent (Rainbow) metrics in a
Relative Locality framework and we show that this formalism is equivalent to
the Hamiltonian formalization of Relative Locality obtained in arXiv:1102.4637.Comment: appears in Proceedings of the 13th Marcell Grossmann meeting on
General Relativity, World Scientific, Singapore, (2014
Quantum Gravity phenomenology and metric formalism
In this proceedings for the MG14 conference, we discuss the construction of a
phenomenology of Planck-scale effects in curved spacetimes, underline a few
open issues and describe some perspectives for the future of this research
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Rainbows without unicorns: Metric structures in theories with Modified Dispersion Relations
Rainbow metrics are a widely used approach to metric formalism for theories
with Modified Dispersion Relations. They have had a huge success in the Quantum
Gravity Phenomenology literature, since they allow to introduce
momentum-dependent spacetime metrics into the description of systems with
Modified Dispersion Relation. In this paper, we introduce the reader to some
realizations of this general idea: the original Rainbow metrics proposal, the
momentum-space-inspired metric, the standard Finsler geometry approach and our
alternative definition of a four-velocity-dependent metric with a massless
limit. This paper aims to highlight some of their properties and how to
properly describe their relativistic realizations.Comment: 10 pages. Discussion on the role of connections was added. Matches
published versio
X-ray and neutron μCT of biomedical samples: from image acquisition to quantification
Even though the validity of x-ray computed tomography in the analysis of biomedical samples is nowadays undisputed, the more recent imaging techniques and more advanced instruments (such as synchrotrons) are still relatively unknown to many medical doctors that could benefit from them.The doctoral work presented in this thesis joins a collective effort from the imaging community to demonstrate potential applications of advanced x-ray and neutron imaging methods to preclinical medical research, with the hope of contributing to reach a “critical mass” in the medical community and in the public opinion as well.Two main lines of work are detailed, one focused on the ex vivo evaluation of corrosion processes of magnesium-based biodegradable implants for osteosynthesis, the other dedicated to the assessment of neuropathy in human gastroenteric dysmotility. The aimed endpoint was to develop pipelines, from image acquisition all the way to data quantification, that could be used by other research groups with similar questions and may inspire future interdisciplinary collaborations between medicine, natural science and engineering.In the first line of work, we have attempted to employ synchrotron-radiation micro-computed tomography (µCT) coupled with in situ loading tests to assess the mechanical properties of the bone-implant interface (Paper I). We have revealed the crucial importance of the radiation dose deposited on the sample, and that the mechanical loading geometry should be accurately determined in the planning steps of the experiment. Moving away from the mechanical testing, we have also explored a novel three-dimensional analysis of the corrosion by-products of biodegradable implants by combining x-ray µCT, neutron µCT and x-ray fluorescence mapping (Papers IV and V). The second line of work has assessed the potential of x-ray phase-contrast µCT and nano-resolution holotomography as ways to perform virtual histology of unstained peripheral and autonomic neural tissue. In full-thickness biopsies of the myenteric nervous system, qualitative and potentially quantitative differences have been shown between controls and patients affected by gastrointestinal dysmotility (Paper II). In unstained skin biopsies, the methods have failed to visualise peripheral nerves, but we could identify structural changes in the connective tissue of some patients when compared to controls and other patients (Paper III)
Science Through the “Golden Security Triangle”: Information Security and Data Journeys in Data-intensive Biomedicine
This paper talks about ways in which infrastructure for biomedical data-intensive discovery is operationalized. Specifically, it is interested in information security solutions and how the processes of scientific research through data-intensive infrastructures are shaped by them. The implications of information security for big data biomedical research have not been discussed in depth by the extant IS literature. Yet, information security might exert a strong influence on the processes and outcomes of data sharing efforts. In this research-in-progress paper I present a developing, in-depth study of a leading information linkage infrastructure that is representative of the kind of opportunities that big data technologies are occasioning in the medical field. This research calls for IS to extend the discussion to consider, building on the empirical detail of intensive case studies, a whole range of relations between provisions for information security and the processes of scientific research and data work
Dual redshift on Planck-scale-curved momentum spaces
Several approaches to the investigation of the quantum-gravity problem have
provided "theoretical evidence" of a role for the Planck scale in
characterizing the geometry of momentum space. One of the main obstructions for
a full exploitation of this scenario is the understanding of the role of the
Planck-scale-curved geometry of momentum space in the correlations between
emission and detection times, the "travel times" for a particle to go from a
given emitter to a given detector. These travel times appear to receive
Planck-scale corrections for which no standard interpretation is applicable,
and the associated implications for spacetime locality gave rise to the notion
of "relative locality" which is still in the early stages of investigation. We
here show that these Planck-scale corrections to travel times can be described
as "dual redshift" (or "lateshift"): they are manifestations of momentum-space
curvature of the same type already known for ordinary redshift produced by
spacetime curvature. In turn we can identify the novel notion of "relative
momentum-space locality" as a known but under-appreciated feature associated to
ordinary redshift produced by spacetime curvature, and this can be described in
complete analogy with the relative spacetime locality that became of interest
in the recent quantum-gravity literature. We also briefly comment on how these
findings may be relevant for an approach to the quantum-gravity problem
proposed by Max Born in 1938 and centered on Born duality.Comment: 13 pages, LaTe
In-vacuo-dispersion features for GRB neutrinos and photons
Over the last 15 years there has been considerable interest in the
possibility of quantum-gravity-induced in-vacuo dispersion, the possibility
that spacetime itself might behave essentially like a dispersive medium for
particle propagation. Two very recent studies have exposed what might be
in-vacuo dispersion features for GRB (gamma-ray-burst) neutrinos of energy in
the range of 100 TeV and for GRB photons with energy in the range of 10 GeV. We
here show that these two features are roughly compatible with a description
such that the same effects apply over 4 orders of magnitude in energy. We also
characterize quantitatively how rare it would be for such features to arise
accidentally, as a result of (still unknown) aspects of the mechanisms
producing photons at GRBs or as a result of background neutrinos accidentally
fitting the profile of a GRB neutrino affected by in-vacuo dispersion.Comment: 12 pages, latex. arXiv admin note: text overlap with arXiv:1609.0398
Hamilton geometry: Phase space geometry from modified dispersion relations
We describe the Hamilton geometry of the phase space of particles whose
motion is characterised by general dispersion relations. In this framework
spacetime and momentum space are naturally curved and intertwined, allowing for
a simultaneous description of both spacetime curvature and non-trivial momentum
space geometry. We consider as explicit examples two models for Planck-scale
modified dispersion relations, inspired from the -de Sitter and
-Poincar\'e quantum groups. In the first case we find the expressions
for the momentum and position dependent curvature of spacetime and momentum
space, while for the second case the manifold is flat and only the momentum
space possesses a nonzero, momentum dependent curvature. In contrast, for a
dispersion relation that is induced by a spacetime metric, as in General
Relativity, the Hamilton geometry yields a flat momentum space and the usual
curved spacetime geometry with only position dependent geometric objects.Comment: 32 pages, section on quantisation of the theory added, comments on
additin of momenta on curved momentum spaces extende
Quantum-gravity-induced dual lensing and IceCube neutrinos
Momentum-space curvature, which is expected in some approaches to the
quantum-gravity problem, can produce dual redshift, a feature which introduces
energy dependence of the travel times of ultrarelativistic particles, and dual
lensing, a feature which mainly affects the direction of observation of
particles. In our recent arXiv:1605.00496 we explored the possibility that dual
redshift might be relevant in the analysis of IceCube neutrinos, obtaining
results which are preliminarily encouraging. Here we explore the possibility
that also dual lensing might play a role in the analysis of IceCube neutrinos.
In doing so we also investigate issues which are of broader interest, such as
the possibility of estimating the contribution by background neutrinos and some
noteworthy differences between candidate "early neutrinos" and candidate "late
neutrinos".Comment: In this version V2 we give a definition of variation probability
which could be considered in alternative to the notion of variation
probability already introduced in version V1; both notions of variation
probability are contemplated in the data analysis. arXiv admin note: text
overlap with arXiv:1605.0049
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