542 research outputs found
Equivalence of the (generalised) Hadamard and microlocal spectrum condition for (generalised) free fields in curved spacetime
We prove that the singularity structure of all n-point distributions of a
state of a generalised real free scalar field in curved spacetime can be
estimated if the two-point distribution is of Hadamard form. In particular this
applies to the real free scalar field and the result has applications in
perturbative quantum field theory, showing that the class of all Hadamard
states is the state space of interest. In our proof we assume that the field is
a generalised free field, i.e. that it satisies scalar (c-number) commutation
relations, but it need not satisfy an equation of motion. The same argument
also works for anti-commutation relations and it can be generalised to
vector-valued fields. To indicate the strengths and limitations of our
assumption we also prove the analogues of a theorem by Borchers and Zimmermann
on the self-adjointness of field operators and of a very weak form of the
Jost-Schroer theorem. The original proofs of these results in the Wightman
framework make use of analytic continuation arguments. In our case no
analyticity is assumed, but to some extent the scalar commutation relations can
take its place.Comment: 18 page
Heavy Ion Collisions at Relativistic Energies: Testing a Nuclear Matter at High Baryon and Isospin Density
We show that the phenomenology of isospin effects on heavy ion reactions at
intermediate energies (few AGeV range) is extremely rich and can allow a
``direct'' study of the covariant structure of the isovector interaction in the
hadron medium. We work within a relativistic transport frame, beyond a cascade
picture, consistently derived from effective Lagrangians, where isospin effects
are accounted for in the mean field and collision terms. Rather sensitive
observables are proposed from collective flows (``differential'' flows) and
from pion/kaon production (, yields). For the latter
point relevant non-equilibrium effects are stressed. The possibility of the
transition to a mixed hadron-quark phase, at high baryon and isospin density,
is finally suggested. Some signatures could come from an expected ``neutron
trapping'' effect.Comment: 8 pages, 4 figures, espcrc1 (latex) style. Conf. "Perspectives in
Hadronic Physics", ICTP Trieste May 2006, Nucl.Phys. A, to appea
Isospin Dynamics in Heavy Ion Collisions: EoS-sensitive Observables
Heavy Ion Collisions (HIC) represent a unique tool to probe the in-medium
nuclear interaction in regions away from saturation and at high nucleon
momenta. In this report we present a selection of reaction observables
particularly sensitive to the isovector part of the interaction, i.e. to the
symmetry term of the nuclear Equation of State (EoS) At low energies the
behavior of the symmetry energy around saturation influences dissipation and
fragment production mechanisms. Predictions are shown for deep-inelastic and
fragmentation collisions induced by neutron rich projectiles. Differential flow
measurements will also shed lights on the controversial neutron/proton
effective mass splitting in asymmetric matter. The high density symmetry term
can be derived from isospin effects on heavy ion reactions at relativistic
energies (few AGeV range), that can even allow a ``direct'' study of the
covariant structure of the isovector interaction in the hadron medium. Rather
sensitive observables are proposed from collective flows and from pion/kaon
production. The possibility of the transition to a mixed hadron-quark phase, at
high baryon and isospin density, is finally suggested. Some signatures could
come from an expected ``neutron trapping'' effect.Comment: 10 pages, 5 figures; espcrc1 style; IX Int.Conf. on Nucleus-Nucleus
Collisions, Rio de Janeiro Aug.2006; to appear in Nucl.Phys.
On the Lorentz structure of the symmetry energy
We investigate in detail the density dependence of the symmetry energy in a
relativistic description by decomposing the iso-vector mean field into
contributions with different Lorentz covariant properties. We find important
effects of the iso-vector, scalar channel (i.e. -meson like) on the
high density behavior of the symmetry energy. Applications to static properties
of finite nuclei and to dynamic situations of heavy ion collisions are explored
and related to each other. The nuclear structure studies show only moderate
effects originating from the virtual meson. At variance, in heavy ion
collisions one finds important contributions on the reaction dynamics arising
from the different Lorentz structure of the high density symmetry energy when a
scalar iso-vector field is introduced. Particularly interesting is the
related neutron/proton effective mass splitting for nucleon transport effects
and for resonance and particle production around the threshold. We show that
the -like channel turns out to be essential for the production of
pions, when comparing with experimental data, in particular for high momentum
selections.Comment: 30 pages, 12 figures (.eps
Heavy ion collisions with non-equilibrium Dirac-Brueckner mean fields
The influence of realistic interactions on the reaction dynamics in
intermediate energy heavy ion collisions is investigated. The mean field in
relativistic transport calculations is derived from microscopic Dirac-Brueckner
(DB) self-energies, taking non-equilibrium effects, in particular the
anisotropy of the local phase space configurations, into account. Thus this
approach goes beyond the local density approximation. A detailed analysis of
various in-plane and out-of-plane flow observables is presented for Au on Au
reactions at incident energies ranging from 250 to 800 A.MeV and the results
are compared to recent measurements of the FOPI collaboration. An overall good
agreement with in-plane flow data and a reasonable description of the
out-of-plane emission is achieved. For these results the intrinsic momentum
dependence of the non-equilibrium mean fields is important. On the other hand,
the local density approximation with the same underlying DB forces as well as a
standard non-linear version of the model are less successful in
describing the present data. This gives evidence of the applicability of self
energies derived from the DB approach to nuclear matter also far from
saturation and equilibrium.Comment: 63 pages Latex, using Elsevier style, 20 ps-figures, to appear in
Nucl. Phys.
Deterministic and stochastic descriptions of gene expression dynamics
A key goal of systems biology is the predictive mathematical description of
gene regulatory circuits. Different approaches are used such as deterministic
and stochastic models, models that describe cell growth and division explicitly
or implicitly etc. Here we consider simple systems of unregulated
(constitutive) gene expression and compare different mathematical descriptions
systematically to obtain insight into the errors that are introduced by various
common approximations such as describing cell growth and division by an
effective protein degradation term. In particular, we show that the population
average of protein content of a cell exhibits a subtle dependence on the
dynamics of growth and division, the specific model for volume growth and the
age structure of the population. Nevertheless, the error made by models with
implicit cell growth and division is quite small. Furthermore, we compare
various models that are partially stochastic to investigate the impact of
different sources of (intrinsic) noise. This comparison indicates that
different sources of noise (protein synthesis, partitioning in cell division)
contribute comparable amounts of noise if protein synthesis is not or only
weakly bursty. If protein synthesis is very bursty, the burstiness is the
dominant noise source, independent of other details of the model. Finally, we
discuss two sources of extrinsic noise: cell-to-cell variations in protein
content due to cells being at different stages in the division cycles, which we
show to be small (for the protein concentration and, surprisingly, also for the
protein copy number per cell) and fluctuations in the growth rate, which can
have a significant impact.Comment: 23 pages, 5 figures; Journal of Statistical physics (2012
Bio-orthogonal Supramolecular Latching inside Live Animals and Its Application for in Vivo Cancer Imaging
© 2019 American Chemical Society.Here, we demonstrate a supramolecular latching tool for bio-orthogonal noncovalent anchoring of small synthetic molecules in live animal models using a fully synthetic high-affinity binding pair between cucurbit[7]uril (CB[7]) and adamantylammonium (AdA). This supramolecular latching system is small (âŒ1 kDa), ensuring efficient uptake into cells, tissues, and whole organisms. It is also chemically robust and resistant to enzymatic degradation and analogous to well-characterized biological systems in terms of noncovalent binding. Occurrence of fluorescence resonance energy transfer (FRET) between cyanine 3-CB[7] (Cy3-CB[7]) and boron-dipyrromethene 630/650X-AdA (BDP630/650-AdA) inside a live worm (Caenorhabditis elegans) indicates efficient in situ high-affinity association between AdA and CB[7] inside live animals. In addition, selective visualization of a cancer site of a live mouse upon supramolecular latching of cyanine 5-AdA (Cy5-AdA) on prelocalized CB[7]-conjugating antibody on the cancer site demonstrates the potential of this synthetic system for in vivo cancer imaging. These findings provide a fresh insight into the development of new chemical biology tools and medical therapeutic systems11sciescopu
Transverse momentum dependence of transverse flow in relativistic heavy-ion collisions
The strength of transverse flow is examined as a function of transverse
momentum using a simple, transversely moving thermal model and a more
realistic, relativistic transport model (ART). It is shown that the
dependence reveals useful information about the collective flow that is
complementary to that obtained from the standard in-plane transverse momentum
analysis. Interesting features of using the dependence to study the
equation of state of the superdense hadronic matter formed in relativistic
heavy-ion collisions are demonstrated.Comment: Latex file, 10 pages, 3 figures availabe upon request; Phys. Rev. C
(Aug., 1996) in pres
Enhanced understanding of non-axisymmetric intrinsic and controlled field impacts in tokamaks
An extensive study of intrinsic and controlled non-axisymmetric field (dB) impacts in KSTAR has enhanced the understanding about non-axisymmetric field physics and its implications, in particular, on resonant magnetic perturbation (RMP) physics and power threshold (Pth) for L-H transition. The n = 1 intrinsic non-axisymmetric field in KSTAR was measured to remain as low as delta B/ B0 x 4 x 10(-5) even at high-beta plasmas (beta(N) similar to 2), which corresponds to approximately 20% below the targeted ITER tolerance level. As for the RMP edge-localized-modes (ELM) control, robust n = 1 RMP ELM-crash-suppression has been not only sustained for more than similar to 90 iota(E), but also confirmed to be compatible with rotating RMP. An optimal window of radial position of lower X-point (i. e. R-x = 1.44 +/- 0.02 m) proved to be quite critical to reach full n = 1 RMP-driven ELM-crash-suppression, while a constraint of the safety factor could be relaxed (q(95) = 5 +/- 0.25). A more encouraging finding was that even when Rx cannot be positioned in the optimal window, another systematic scan in the vicinity of the previously optimal Rx allows for a new optimal window with relatively small variations of plasma parameters. Also, we have addressed the importance of optimal phasing (i. e. toroidal phase difference between adjacent rows) for n = 1 RMP-driven ELM control, consistent with an ideal plasma response modeling which could predict phasing-dependent ELM suppression windows. In support of ITER RMP study, intentionally misaligned RMPs have been found to be quite effective during ELMmitigation stage in lowering the peaks of divertor heat flux, as well as in broadening the ` wet' areas. Besides, a systematic survey of Pth dependence on non-axisymmetric field has revealed the potential limit of the merit of low intrinsic non-axisymmetry. Considering that the ITER RMP coils are composed of 3-rows, just like in KSTAR, further 3D physics study in KSTAR is expected to help us minimize the uncertainties of the ITER RMP coils, as well as establish an optimal 3D configuration for ITER and future reactors
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