1,035 research outputs found
Some comments on the universal constant in DSR
Deformed Special Relativity is usually presented as a deformation of Special
Relativity accommodating a new universal constant, the Planck mass, while
respecting the relativity principle. In order to avoid some fundamental
problems (e.g. soccer ball problem), we argue that we should switch point of
view and consider instead the Newton constant as the universal constant.Comment: 12 pages, Proceedings of DICE2006 (Piombino, Italy
And what if gravity is intrinsically quantic ?
Since the early days of search for a quantum theory of gravity the attempts
have been mostly concentrated on the quantization of an otherwise classical
system. The two most contentious candidate theories of gravity, sting theory
and quantum loop gravity are based on a quantum field theory - the latter is a
quantum field theory of connections on a SU(2) group manifold and former a
quantum field theory in two dimensional spaces. Here we argue that there is a
very close relation between quantum mechanics and gravity. Without gravity
quantum mechanics becomes ambiguous. We consider this observation as the
evidence for an intrinsic relation between these fundamental laws of nature. We
suggest a quantum role and definition for gravity in the context of a quantum
universe, and present a preliminary formulation for gravity in a system with a
finite number of particles.Comment: 8 pages, 1 figure. To appear in the proceedings of the DICE2008
conference, Castiglioncello, Tuscany, Italy, 22-26 Sep. 2008. V2: some typos
remove
Maximally Localized States in Quantum Mechanics with a Modified Commutation Relation to All Orders
We construct the states of maximal localization taking into account a
modification of the commutation relation between position and momentum
operators to all orders of the minimum length parameter. To first order, the
algebra we use reproduces the one proposed by Kempft, Mangano and Mann. It is
emphasized that a minimal length acts as a natural regulator for the theory,
thus eliminating the otherwise ever appearing infinities. So, we use our
results to calculate the first correction to the Casimir Effect due to the
minimal length. We also discuss some of the physical consequences of the
existence of a minimal length, culminating in a proposal to reformulate the
very concept of "position measurement"
Singular topologies in the Boulatov model
Through the question of singular topologies in the Boulatov model, we
illustrate and summarize some of the recent advances in Group Field Theory.Comment: 4 pages; proceedings of Loops'11 (May 2011, Madrid); v2: minor
modifications matching published versio
Holonomic quantum computation in the presence of decoherence
We present a scheme to study non-abelian adiabatic holonomies for open
Markovian systems. As an application of our framework, we analyze the
robustness of holonomic quantum computation against decoherence. We pinpoint
the sources of error that must be corrected to achieve a geometric
implementation of quantum computation completely resilient to Markovian
decoherence.Comment: I. F-G. Now publishes under name I. Fuentes-Schuller Published
versio
From perceived autonomy support to intentional behaviour: Testing an integrated model in three healthy-eating behaviours
A motivational model integrating self-determination theory, the theory of planned behaviour, and the health action process approach was tested in three samples in three behavioural contexts: fruit and vegetable, breakfast, and snack consumption. Perceived support for autonomous (self-determined) forms of motivation from parents and autonomous motivation from self-determination theory were hypothesised to predict intention and behaviour indirectly via the mediation of attitude and perceived behavioural control from the theory of planned behaviour. It was also expected that planning strategies would mediate the effect of intention on behaviour. Relations in the proposed models were expected to be similar across the behaviours. A two-wave prospective design was adopted. Three samples of high-school students (total N = 1041; 59.60% female; M age = 17.13 years ± 1.57) completed measures of perceived autonomy support, autonomous motivation, theory of planned behaviour constructs, planning strategies and behaviour for each of the three behavioural contexts. Three months later, 816 participants (62,24% female; M age: 17.13 years, SD = 1.58) of the initial sample self-reported their behaviour referred to the previous three months. Structural equation models provided support for the key hypothesised effects of the proposed model for the three health-related behaviours. Two direct effects were significantly different across the three behaviours: the effect of perceived autonomy support on perceived behavioural control and the effect of attitude on intention. In addition, planning strategies mediated the effect of intention on behaviour in fruit and vegetable sample only. Findings extend knowledge of the processes by which psychological antecedents from the theories affect energy-balance related behaviours
Gravitational dynamics in Bose Einstein condensates
Analogue models for gravity intend to provide a framework where matter and
gravity, as well as their intertwined dynamics, emerge from degrees of freedom
that have a priori nothing to do with what we call gravity or matter. Bose
Einstein condensates (BEC) are a natural example of analogue model since one
can identify matter propagating on a (pseudo-Riemannian) metric with collective
excitations above the condensate of atoms. However, until now, a description of
the "analogue gravitational dynamics" for such model was missing. We show here
that in a BEC system with massive quasi-particles, the gravitational dynamics
can be encoded in a modified (semi-classical) Poisson equation. In particular,
gravity is of extreme short range (characterized by the healing length) and the
cosmological constant appears from the non-condensed fraction of atoms in the
quasi-particle vacuum. While some of these features make the analogue
gravitational dynamics of our BEC system quite different from standard
Newtonian gravity, we nonetheless show that it can be used to draw some
interesting lessons about "emergent gravity" scenarios.Comment: Replaced with published version. 15 pages, no figures, revtex4.
Reference adde
Density fluctuations in -deformed inflationary universe
We study the spectrum of metric fluctuation in -deformed inflationary
universe. We write the theory of scalar metric fluctuations in the
deformed Robertson-Walker space, which is represented as a non-local
theory in the conventional Robertson-Walker space. One important consequence of
the deformation is that the mode generation time is naturally determined by the
structure of the deformation.
We expand the non-local action in , with being the Hubble
parameter and the deformation parameter, and then compute the power
spectra of scalar metric fluctuations both for the cases of exponential and
power law inflations up to the first order in . We show that the
power spectra of the metric fluctuation have non-trivial corrections on the
time dependence and on the momentum dependence compared to the commutative
space results. Especially for the power law inflation case, the power spectrum
for UV modes is weakly blue shifted early in the inflation and its strength
decreases in time. The power spectrum of far-IR modes has cutoff proportional
to which may explain the low CMB quadrupole moment.Comment: final revision; 19 pages, 3 figures; to appear in Phys. Rev.
An algebraic Birkhoff decomposition for the continuous renormalization group
This paper aims at presenting the first steps towards a formulation of the
Exact Renormalization Group Equation in the Hopf algebra setting of Connes and
Kreimer. It mostly deals with some algebraic preliminaries allowing to
formulate perturbative renormalization within the theory of differential
equations. The relation between renormalization, formulated as a change of
boundary condition for a differential equation, and an algebraic Birkhoff
decomposition for rooted trees is explicited
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