1,271 research outputs found
Hawking Radiation from Fluctuating Black Holes
Classically, black Holes have the rigid event horizon. However, quantum
mechanically, the event horizon of black holes becomes fuzzy due to quantum
fluctuations. We study Hawking radiation of a real scalar field from a
fluctuating black hole. To quantize metric perturbations, we derive the
quadratic action for those in the black hole background. Then, we calculate the
cubic interaction terms in the action for the scalar field. Using these
results, we obtain the spectrum of Hawking radiation in the presence of
interaction between the scalar field and the metric. It turns out that the
spectrum deviates from the Planck spectrum due to quantum fluctuations of the
metric.Comment: 35pages, 4 figure
New working spaces. Policy perspectives before and after the COVID-19 pandemic
This chapter maps the debate of new working spaces (particularly CSs) on
the level of European policy making. It explores how new working spaces
have been interpreted by the European Commission and how this debate
has evolved from its origins up to the recent COVID-19 period. For these
purposes, two diferent ideas of CSs will be presented and discussed: CSs as
innovation drivers boosting economic development; and as opportunities for
territorial regeneration, such as brownfeld redevelopment or local hubs promoting
social cohesion. Specifc attention is devoted to identifying the evolution
of policies supporting these spaces with a focus on place-based and urban
planning measures before and during the COVID-19 pandemic. This chapter
empirically investigates this debate analyzing EU policy reports and case studies.
Finally, remarks and suggestions for policy learning are presented
Static black hole solutions with a self interacting conformally coupled scalar field
We study static, spherically symmetric black hole solutions of the Einstein
equations with a positive cosmological constant and a conformally coupled self
interacting scalar field. Exact solutions for this model found by
Mart{\'\i}nez, Troncoso, and Zanelli, (MTZ), were subsequently shown to be
unstable under linear perturbations, with modes that diverge arbitrarily fast.
We find that the moduli space of static, spherically symmetric solutions that
have a regular horizon -and satisfy the weak and dominant energy conditions
outside the horizon- is a singular subset of a two dimensional space
parameterized by the horizon radius and the value of the scalar field at the
horizon. The singularity of this space of solutions provides an explanation for
the instability of the MTZ spacetimes, and leads to the conclusion that, if we
include stability as a criterion, there are no physically acceptable black hole
solutions for this system that contain a cosmological horizon in the exterior
of its event horizon.Comment: 22 pages, 5 figures (replaced figure #4), final version, to be
published in PR
Duality between simple-group gauge theories and some applications
In this paper we investigate N=1 supersymmetric gauge theories with a product
gauge group. By using smoothly confining dynamics, we can find new dualities
which include higher-rank tensor fields, and in which the dual gauge group is
simple, not a product. Some of them are dualities between chiral and non-chiral
gauge theories. We also discuss some applications to dynamical supersymmetry
breaking phenomena and new confining theories with a tree-level superpotential.Comment: 33 pages, LaTeX, references added, version to appear in PR
Supersymmetric Gauge Theories with an Affine Quantum Moduli Space
All supersymmetric gauge theories based on simple groups which have an affine
quantum moduli space, i.e. one generated by gauge invariants with no relations,
W=0, and anomaly matching at the origin, are classified. It is shown that the
only theories with no gauge invariants (and moduli space equal to a single
point) are the two known examples, SU(5) with 5-bar + 10 and SO(10) with a
spinor. The index of the matter representation must be at least as big as the
index of the adjoint in theories which have a non-trivial relation among the
gauge invariants.Comment: Incorrect proof that theories with constraints must have mu >=
mu(adj) replaced by a correct one (6 pages, uses revtex, amssymb, array
The dynamical evolution of protoplanetary disks and planets in dense star clusters
Most stars are born in dense stellar environments where the formation and
early evolution of planetary systems may be significantly perturbed by
encounters with neighbouring stars. To investigate on the fate of circumstellar
gas disks and planets around young stars dense stellar environments, we
numerically evolve star-disk-planet systems. We use the -body codes
NBODY6++GPU and SnIPES for the dynamical evolution of the stellar population,
and the SPH-based code GaSPH for the dynamical evolution of protoplanetary
disks. The secular evolution of a planetary system in a cluster differs from
that of a field star. Most stellar encounters are tidal, adiabatic and
nearly-parabolic. The parameters that characterize the impact of an encounter
include the orientation of the protoplanetary disk and planet relative to the
orbit of the encountering star, and the orbital phase and the semi-major axis
of the planet. We investigate this dependence for close encounters (, where is the periastron distance of the encountering star and
is the semi-major axis of the planet). We also investigate distant perturbers
(), which have a moderate effect on the dynamical evolution of
the planet and the protoplanetary disk. We find that the evolution of
protoplanetary disks in star clusters differs significantly from that of
isolated systems. When interpreting the outcome of the planet formation
process, it is thus important to consider their birth environments.Comment: 14 Pages, 11 Figures, Accepted for pubblication on MNRAS on 13
September 202
Oncolytic virus expressing RANTES and IL-15 enhances function of CAR-modified T cells in solid tumors
We improved the migration and survival of chimeric antigen receptor (CAR)-modified T cells in solid tumors by combining CAR-T cells with an armed oncolytic virus. Local delivery of the chemokine RANTES and the cytokine IL-15 by the oncolytic virus enhanced the trafficking and persistence of the CAR-T cells, resulting in improved antitumor effects
On alternative approaches to Lorentz violation in loop quantum gravity inspired models
Recent claims point out that possible violations of Lorentz symmetry
appearing in some semiclassical models of extended matter dynamics motivated by
loop quantum gravity can be removed by a different choice of canonically
conjugated variables. In this note we show that such alternative is
inconsistent with the choice of variables in the underlying quantum theory
together with the semiclassical approximation, as long as the correspondence
principle is maintained. A consistent choice will violate standard Lorentz
invariance. Thus, to preserve a relativity principle in this framework, the
linear realization of Lorentz symmetry should be extended or superseded.Comment: 4 pages, revtex4, no figures, references adde
Linking the formation and fate of exo-Kuiper belts within solar system analogues
Abstract Escalating observations of exo-minor planets and their destroyed remnants both passing through the solar system and within white dwarf planetary systems motivate an understanding of the orbital history and fate of exo-Kuiper belts and planetesimal discs. Here we explore how the structure of a 40 − 1000 au annulus of planetesimals orbiting inside of a solar system analogue that is itself initially embedded within a stellar cluster environment varies as the star evolves through all of its stellar phases. We attempt this computationally challenging link in four parts: (1) by performing stellar cluster simulations lasting 100 Myr, (2) by making assumptions about the subsequent quiescent 11 Gyr main-sequence evolution, (3) by performing simulations throughout the giant branch phases of evolution, and (4) by making assumptions about the belt’s evolution during the white dwarf phase. Throughout these stages, we estimate the planetesimals’ gravitational responses to analogues of the four solar system giant planets, as well as to collisional grinding, Galactic tides, stellar flybys, and stellar radiation. We find that the imprint of stellar cluster dynamics on the architecture of ≳ 100 km-sized exo-Kuiper belt planetesimals is retained throughout all phases of stellar evolution unless violent gravitational instabilities are triggered either (1) amongst the giant planets, or (2) due to a close (≪103 au) stellar flyby. In the absence of these instabilities, these minor planets simply double their semimajor axis while retaining their primordial post-cluster eccentricity and inclination distributions, with implications for the free-floating planetesimal population and metal-polluted white dwarfs
Spreading in narrow channels
We study a lattice model for the spreading of fluid films, which are a few
molecular layers thick, in narrow channels with inert lateral walls. We focus
on systems connected to two particle reservoirs at different chemical
potentials, considering an attractive substrate potential at the bottom,
confining side walls, and hard-core repulsive fluid-fluid interactions. Using
kinetic Monte Carlo simulations we find a diffusive behavior. The corresponding
diffusion coefficient depends on the density and is bounded from below by the
free one-dimensional diffusion coefficient, valid for an inert bottom wall.
These numerical results are rationalized within the corresponding continuum
limit.Comment: 16 pages, 10 figure
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