4,833 research outputs found
An operator expansion for integrable quantum field theories
A large class of quantum field theories on 1+1 dimensional Minkowski space,
namely, certain integrable models, has recently been constructed rigorously by
Lechner. However, the construction is very abstract and the concrete form of
local observables in these models remains largely unknown. Aiming for more
insight into their structure, we establish a series expansion for observables,
similar but not identical to the well-known form factor expansion. This
expansion will be the basis for a characterization and explicit construction of
local observables, to be discussed elsewhere. Here, we establish the expansion
independent of the localization aspect, and analyze its behavior under
space-time symmetries. We also clarify relations with deformation methods in
quantum field theory, specifically, with the warped convolution in the sense of
Buchholz and Summers.Comment: minor corrections and clarifications, as published in J. Phys A; 24
page
EIT ground-state cooling of long ion strings
Electromagnetically-induced-transparency (EIT) cooling is a ground-state
cooling technique for trapped particles. EIT offers a broader cooling range in
frequency space compared to more established methods. In this work, we
experimentally investigate EIT cooling in strings of trapped atomic ions. In
strings of up to 18 ions, we demonstrate simultaneous ground state cooling of
all radial modes in under 1 ms. This is a particularly important capability in
view of emerging quantum simulation experiments with large numbers of trapped
ions. Our analysis of the EIT cooling dynamics is based on a novel technique
enabling single-shot measurements of phonon numbers, by rapid adiabatic passage
on a vibrational sideband of a narrow transition
Direct determination of vibrational density of states change on ligand binding to a protein
The change in the vibrational density of states of a protein (dihydrofolate reductase) on binding a ligand (methotrexate) is determined using inelastic neutron scattering. The vibrations of the complex soften significantly relative to the unbound protein. The resulting free-energy change, which is directly determined by the density of states change, is found to contribute significantly to the binding equilibrium
Entrepreneurial value creation: conceptualizing an exchange-based view of entrepreneurship
4sìopenPurpose: This paper proposes an Exchange-Based View of the value creation process. The Borrowing from marketing literature, the EBV advances that entrepreneurs and stakeholders are tied by exchange relationships, through which they co-create value by reciprocally making and realizing promises of value. Design/methodology/approach: Propositions are developed and offered to advance the role of exchange in the entrepreneurial value creation process. Findings: The authors conceptualize the enterprise as a system of exchange relationships between entrepreneurs and their stakeholders, thus proposing an exchange-based view of entrepreneurship. Originality/value: Such an account of the role of entrepreneurs and of their relationship with the stakeholders has meaningful implications for our understanding of the entrepreneurial tasks of opportunity recognition and exploitation.openPinelli M.; Lechner C.; Kraus S.; Liguori E.Pinelli, M.; Lechner, C.; Kraus, S.; Liguori, E
Deformations of Fermionic Quantum Field Theories and Integrable Models
Considering the model of a scalar massive Fermion, it is shown that by means
of deformation techniques it is possible to obtain all integrable quantum field
theoretic models on two-dimensional Minkowski space which have factorizing
S-matrices corresponding to two-particle scattering functions S_2 satisfying
S_2(0) = -1. Among these models there is for example the Sinh-Gordon model. Our
analysis provides a complement to recent developments regarding deformations of
quantum field theories. The deformed model is investigated also in higher
dimensions. In particular, locality and covariance properties are analyzed.Comment: 20 page
Optical Spectroscopy of IRAS 02091+6333
We present a detailed spectroscopic investigation, spanning four winters, of
the asymptotic giant branch (AGB) star IRAS 02091+6333. Zijlstra & Weinberger
(2002) found a giant wall of dust around this star and modelled this unique
phenomenon. However their work suffered from the quality of the optical
investigations of the central object. Our spectroscopic investigation allowed
us to define the spectral type and the interstellar foreground extinction more
precisely. Accurate multi band photometry was carried out. This provides us
with the possibility to derive the physical parameters of the system. The
measurements presented here suggest a weak irregular photometric variability of
the target, while there is no evidence of a spectroscopic variability over the
last four years.Comment: 5 pages, Latex, 3 tables, 4 figures, Astron. & Astrophys. - in pres
Partial Homology Relations - Satisfiability in terms of Di-Cographs
Directed cographs (di-cographs) play a crucial role in the reconstruction of
evolutionary histories of genes based on homology relations which are binary
relations between genes. A variety of methods based on pairwise sequence
comparisons can be used to infer such homology relations (e.g.\ orthology,
paralogy, xenology). They are \emph{satisfiable} if the relations can be
explained by an event-labeled gene tree, i.e., they can simultaneously co-exist
in an evolutionary history of the underlying genes. Every gene tree is
equivalently interpreted as a so-called cotree that entirely encodes the
structure of a di-cograph. Thus, satisfiable homology relations must
necessarily form a di-cograph. The inferred homology relations might not cover
each pair of genes and thus, provide only partial knowledge on the full set of
homology relations. Moreover, for particular pairs of genes, it might be known
with a high degree of certainty that they are not orthologs (resp.\ paralogs,
xenologs) which yields forbidden pairs of genes. Motivated by this observation,
we characterize (partial) satisfiable homology relations with or without
forbidden gene pairs, provide a quadratic-time algorithm for their recognition
and for the computation of a cotree that explains the given relations
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