1,600 research outputs found
The digital transformation of work: a relational view
Conversation about the current and potential effects of digital technologies on the nature of work is raging within scholarly and practitioner communities. Artificial intelligence, robotics, data analytics, digital platforms, and automation, among other technologies, are prompting a swift and profound transformation of work. Building on Pierpaolo Donati''s relational sociology, we examine the changes these technologies are likely to bring about in work as a human relation. Despite the very real threats of unemployment, job insecurity, precariousness, and surveillance, technology may also encourage the emergence of a work culture that shifts the scales toward a relational realm rather than a transactional one. To this end, we argue that work should be understood as a social relation with four dimensions: exchange value, intrinsic extra-economic purpose, communication for reciprocal services, and correspondence with primary human needs according to use values. Understanding the digital transformation of work from this point of view requires comprehending the differentiation and integration of these four dimensions
Inversion of statistics and thermalization in the Unruh effect
We derive a master equation for the reduced density matrix of a uniformly
accelerating quantum detector in arbitrary dimensions, generically coupled to a
field initially in its vacuum state, and analyze its late time regime. We find
that such density matrix asymptotically reaches a Gibbs state. The
particularities of its evolution towards this state are encoded in the response
function, which depends on the dimension, the properties of the fields, and the
specific coupling to them. We also compare this situation with the
thermalization of a static detector immersed in a thermal field state,
pinpointing the differences between both scenarios. In particular, we analyze
the role of the response function and its effect on the evolution of the
detector towards equilibrium. Furthermore, we explore the consequences of the
well-known statistics inversion of the response function of an Unruh-DeWitt
detector linearly coupled to a free scalar field in odd spacetime dimensions.
This allows us to precise in which sense accelerated detectors in Minkowski
vacuum behave as static detectors in a thermal bath and in which sense they do
not.Comment: 9 pages, no figure
Emergent gauge symmetries: Yang-Mills theory
Gauge symmetries remove unphysical states and guarantee that field theories
are free from the pathologies associated with these states. In this work we
find a set of general conditions that guarantee the removal of unphysical
states in field theories describing interacting vector fields. These conditions
are obtained through the extension of a mechanism for the emergence of gauge
symmetries proposed in a previous article [C. Barcel\'o et al. JHEP 10 (2016)
084] in order to account for non-Abelian gauge symmetries, and are the
following: low-energy Lorentz invariance, emergence of massless vector fields
describable by an action quadratic in those fields and their derivatives, and
self-coupling to a conserved current associated with specific rigid symmetries.
Using a bootstrapping procedure, we prove that these conditions are equivalent
to the emergence of gauge symmetries and, therefore, guarantee that any theory
satisfying them must be equivalent to a Yang-Mills theory at low energies.Comment: 15 pages, no figures; v2: Added minor changes in text to match
published versio
General Relativity as an Attractor in Scalar-Tensor Stochastic Inflation
Quantum fluctuations of scalar fields during inflation could determine the
very large-scale structure of the universe. In the case of general
scalar-tensor gravity theories these fluctuations lead to the diffusion of
fundamental constants like the Planck mass and the effective Brans--Dicke
parameter, . In the particular case of Brans--Dicke gravity, where
is constant, this leads to runaway solutions with infinitely large
values of the Planck mass. However, in a theory with variable we find
stationary probability distributions with a finite value of the Planck mass
peaked at exponentially large values of after inflation. We conclude
that general relativity is an attractor during the quantum diffusion of the
fields.Comment: LaTeX (with RevTex) 11 pages, 2 uuencoded figures appended, also
available on WWW via http://star.maps.susx.ac.uk/index.htm
STATIONARY SOLUTIONS IN BRANS-DICKE STOCHASTIC INFLATIONARY COSMOLOGY
In Brans-Dicke theory the Universe becomes divided after inflation into many
exponentially large domains with different values of the effective
gravitational constant. Such a process can be described by diffusion equations
for the probability of finding a certain value of the inflaton and dilaton
fields in a physical volume of the Universe. For a typical chaotic inflation
potential, the solutions for the probability distribution never become
stationary but grow forever towards larger values of the fields. We show here
that a non-minimal conformal coupling of the inflaton to the curvature scalar,
as well as radiative corrections to the effective potential, may provide a
dynamical cutoff and generate stationary solutions. We also analyze the
possibility of large nonperturbative jumps of the fluctuating inflaton scalar
field, which was recently revealed in the context of the Einstein theory. We
find that in the Brans--Dicke theory the amplitude of such jumps is strongly
suppressed.Comment: 19 pages, LaTe
A molecular survey of outflow gas: velocity-dependent shock chemistry and the peculiar composition of the EHV gas
(Abridged) We present a molecular survey of the outflows powered by L1448-mm
and IRAS 04166+2706, two sources with prominent wing and extremely high
velocity (EHV) components in their CO spectra. The molecular composition of the
two outflows presents systematic changes with velocity that we analyze by
dividing the outflow in three chemical regimes, two of them associated with the
wing component and the other the EHV gas. The analysis of the two wing regimes
shows that species like H2CO and CH3OH favor the low-velocity gas, while SiO
and HCN are more abundant in the fastest gas. We also find that the EHV regime
is relatively rich in O-bearing species, as is not only detected in CO and SiO
(already reported elsewhere), but also in SO, CH3OH, and H2CO (newly reported
here), with a tentative detection in HCO+. At the same time, the EHV regime is
relatively poor in C-bearing molecules like CS and HCN. We suggest that this
difference in composition arises from a lower C/O ratio in the EHV gas. The
different chemical compositions of the wing and EHV regimes suggest that these
two outflow components have different physical origins. The wing component is
better explained by shocked ambient gas, although none of the existing shock
models explains all observed features. The peculiar composition of the EHV gas
may reflect its origin as a dense wind from the protostar or its surrounding
disk.Comment: 20 pages, 14 figures. Accepted by Astronomy and Astrophysic
Theoretical Foundation of the Control of Pollination by Hoverflies in a Greenhouse
We propose a conceptual model for pollination and fertilization of tomato flowers in greenhouses crops by hoverflies, when the maximal number of adult pollinators maintained by the crops is less than what is needed for an economically successful pollination in greenhouses. The model consists of a two-stage process for additional feeding of hoverfly to maintain the pollinator density at the economically desired level. First, with a stochastic model, we calculate the density of flies necessary for the economically successful pollination, determined according to the economically expected yield. Second, using a deterministic optimal control model, we find a minimum cost supplementary feeding strategy. In summary, we theoretically demonstrate, at the present stage of the research without validations in case studies, that optimal supplementary feeding can maintain the economically desired hoverfly density
A wide-angle outflow with the simultaneous presence of a high-velocity jet in the high-mass Cepheus A HW2 system
We present five epochs of VLBI water maser observations around the massive
protostar Cepheus A HW2 with 0.4 mas (0.3 AU) resolution. The main goal of
these observations was to follow the evolution of the remarkable water maser
linear/arcuate structures found in earlier VLBI observations. Comparing the
data of our new epochs of observation with those observed five years before, we
find that at "large" scales of > 1" (700 AU) the main regions of maser emission
persist, implying that both the surrounding medium and the exciting sources of
the masers have been relatively stable during that time span. However, at
smaller scales of < 0.1" (70 AU) we see large changes in the maser structures,
particularly in the expanding arcuate structures R4 and R5. R4 traces a nearly
elliptical patchy ring of ~ 70 mas size (50 AU) with expanding motions of ~ 5
mas/yr (15 km/s). This structure is probably driven by the wind of a still
unidentified YSO located at the centre of the ring (~ 0.18" south of HW2). On
the other hand, the R5 expanding bubble structure (driven by the wind of a
previously identified YSO located ~ 0.6" south of HW2) is currently dissipating
in the circumstellar medium and losing its previous degree of symmetry,
indicating a very short-lived event. In addition, our results reveal, at scales
of ~ 1" (700 AU), the simultaneous presence of a relatively slow (~ 10-70 km/s)
wide-angle outflow (opening angle of ~ 102 deg, traced by the masers, and the
fast (~ 500~km/s) highly collimated radio jet associated with HW2 (opening
angle of ~ 18 deg, previously observed with the VLA. This simultaneous presence
of a wide-angle outflow and a highly collimated jet associated with a massive
protostar is similar to what is found in some low-mass YSOs. The implications
of these results in the study of the formation of high-mass stars are
discussed.Comment: 28 pages, 7 figures. Animations will be included as supporting
material online (MNRAS web page
Constraints from Inflation on Scalar-Tensor Gravity Theories
We show how observations of the perturbation spectra produced during
inflation may be used to constrain the parameters of general scalar-tensor
theories of gravity, which include both an inflaton and dilaton field. An
interesting feature of these models is the possibility that the curvature
perturbations on super-horizon scales may not be constant due to non-adiabatic
perturbations of the two fields. Within a given model, the tilt and relative
amplitude of the scalar and tensor perturbation spectra gives constraints on
the parameters of the gravity theory, which may be comparable with those from
primordial nucleosynthesis and post-Newtonian experiments.Comment: LaTeX (with RevTex) 19 pages, 8 uuencoded figures appended, also
available on WWW via http://star.maps.susx.ac.uk/index.htm
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