275 research outputs found
Dimensional Reduction in Non-Supersymmetric Theories
It is shown that regularisation by dimensional reduction is a viable
alternative to dimensional regularisation in non-supersymmetric theories.Comment: 13 pages, phyzzx, LTH 32
Recommended from our members
Recommendations From the International Consortium on Professional Nursing Practice in Long-Term Care Homes
In response to the International Association of Gerontology and Geriatrics’ global agenda for clinical research and quality of care in nursing homes, the International Consortium on Professional Nursing Practice in Long Term Care Homes (the Consortium) was formed to develop nursing leadership capacity in nursing homes and address the concerns regarding the current state of nursing leadership in long-term care homes (LTCHs). At its invitational, two-day inaugural meeting, the Consortium brought together international nurse experts to explore the potential of registered nurses (RNs) who work as supervisors or charge nurses within the LTCHs and the value of their contribution in nursing homes, consider what RN competencies might be needed, discuss effective educational (curriculum and practice) experiences, health care policy, and human resources planning requirements, and to identify what sustainable nurse leadership strategies and models might enhance the effectiveness of RNs in improving resident, family, and staff outcomes.
The Consortium made recommendations about the following priority issues for action: (1) define the competencies of RNs required to care for older adults in LTCH; (2) create a LTCH environment where the RN role is differentiated from other team members and they can practice to their full scope; and (3) prepare RN leaders to operate effectively in person-centered care LTCH environments. In addition to clear recommendations for practice, the consortium identified several areas where further research is needed. The research agenda the consortium advocated for emphasizes an international coordination of research efforts to explore similar issues, the pursuit of examining the impact of nursing and organizational models, and the showcasing of excellence in nursing practice in care homes, so that others might learn from what works. Several studies already underway will also be described
Twistor Strings with Flavour
We explore the tree-level description of a class of N=2 UV-finite SYM
theories with fundamental flavour within a topological B-model twistor string
framework. In particular, we identify the twistor dual of the Sp(N) gauge
theory with one antisymmetric and four fundamental hypermultiplets, as well as
that of the SU(N) theory with 2N hypermultiplets. This is achieved by suitably
orientifolding/orbifolding the original N=4 setup of Witten and adding a
certain number of new topological 'flavour'-branes at the orientifold/orbifold
fixed planes to provide the fundamental matter. We further comment on the
appearance of these objects in the B-model on CP(3|4). An interesting aspect of
our construction is that, unlike the IIB description of these theories in terms
of D3 and D7-branes, on the twistor side part of the global flavour symmetry is
realised geometrically. We provide evidence for this correspondence by
calculating and matching amplitudes on both sides.Comment: 38+12 pages; uses axodraw.sty. v2: References added, minor
clarification
Dynamics with Infinitely Many Derivatives: The Initial Value Problem
Differential equations of infinite order are an increasingly important class
of equations in theoretical physics. Such equations are ubiquitous in string
field theory and have recently attracted considerable interest also from
cosmologists. Though these equations have been studied in the classical
mathematical literature, it appears that the physics community is largely
unaware of the relevant formalism. Of particular importance is the fate of the
initial value problem. Under what circumstances do infinite order differential
equations possess a well-defined initial value problem and how many initial
data are required? In this paper we study the initial value problem for
infinite order differential equations in the mathematical framework of the
formal operator calculus, with analytic initial data. This formalism allows us
to handle simultaneously a wide array of different nonlocal equations within a
single framework and also admits a transparent physical interpretation. We show
that differential equations of infinite order do not generically admit
infinitely many initial data. Rather, each pole of the propagator contributes
two initial data to the final solution. Though it is possible to find
differential equations of infinite order which admit well-defined initial value
problem with only two initial data, neither the dynamical equations of p-adic
string theory nor string field theory seem to belong to this class. However,
both theories can be rendered ghost-free by suitable definition of the action
of the formal pseudo-differential operator. This prescription restricts the
theory to frequencies within some contour in the complex plane and hence may be
thought of as a sort of ultra-violet cut-off.Comment: 40 pages, no figures. Added comments concerning fractional operators
and the implications of restricting the contour of integration. Typos
correcte
The Complete Solution of 2D Superfield Supergravity from graded Poisson-Sigma Models and the Super Pointparticle
Recently an alternative description of 2d supergravities in terms of graded
Poisson-Sigma models (gPSM) has been given. As pointed out previously by the
present authors a certain subset of gPSMs can be interpreted as "genuine"
supergravity, fulfilling the well-known limits of supergravity, albeit deformed
by the dilaton field. In our present paper we show that precisely that class of
gPSMs corresponds one-to-one to the known dilaton supergravity superfield
theories presented a long time ago by Park and Strominger. Therefore, the
unique advantages of the gPSM approach can be exploited for the latter: We are
able to provide the first complete classical solution for any such theory. On
the other hand, the straightforward superfield formulation of the point
particle in a supergravity background can be translated back into the gPSM
frame, where "supergeodesics" can be discussed in terms of a minimal set of
supergravity field degrees of freedom. Further possible applications like the
(almost) trivial quantization are mentioned.Comment: 48 pages, 1 figure. v3: after final version, typos correcte
Baryon polarization in low-energy unpolarized meson-baryon scattering
We compute the polarization of the final-state baryon, in its rest frame, in
low-energy meson--baryon scattering with unpolarized initial state, in
Unitarized BChPT. Free parameters are determined by fitting total and
differential cross-section data (and spin-asymmetry or polarization data if
available) for , and scattering. We also compare our
results with those of leading-order BChPT
Cosmological Non-Linearities as an Effective Fluid
The universe is smooth on large scales but very inhomogeneous on small
scales. Why is the spacetime on large scales modeled to a good approximation by
the Friedmann equations? Are we sure that small-scale non-linearities do not
induce a large backreaction? Related to this, what is the effective theory that
describes the universe on large scales? In this paper we make progress in
addressing these questions. We show that the effective theory for the
long-wavelength universe behaves as a viscous fluid coupled to gravity:
integrating out short-wavelength perturbations renormalizes the homogeneous
background and introduces dissipative dynamics into the evolution of
long-wavelength perturbations. The effective fluid has small perturbations and
is characterized by a few parameters like an equation of state, a sound speed
and a viscosity parameter. These parameters can be matched to numerical
simulations or fitted from observations. We find that the backreaction of
small-scale non-linearities is very small, being suppressed by the large
hierarchy between the scale of non-linearities and the horizon scale. The
effective pressure of the fluid is always positive and much too small to
significantly affect the background evolution. Moreover, we prove that
virialized scales decouple completely from the large-scale dynamics, at all
orders in the post-Newtonian expansion. We propose that our effective theory be
used to formulate a well-defined and controlled alternative to conventional
perturbation theory, and we discuss possible observational applications.
Finally, our way of reformulating results in second-order perturbation theory
in terms of a long-wavelength effective fluid provides the opportunity to
understand non-linear effects in a simple and physically intuitive way.Comment: 84 pages, 3 figure
Interferon-β gene transfer induces a strong cytotoxic bystander effect on melanoma cells
A local gene therapy scheme for the delivery of type I interferons could be an alternative for the treatment of melanoma. We evaluated the cytotoxic effects of interferon-β (IFNβ) gene lipofection on tumor cell lines derived from three human cutaneous and four canine mucosal melanomas. The cytotoxicity of human IFNβ gene lipofection resulted higher or equivalent to that of the corresponding addition of the recombinant protein (rhIFNβ) to human cells. IFNβ gene lipofection was not cytotoxic for only one canine melanoma cell line. When cultured as monolayers, three human and three canine IFNβ-lipofected melanoma cell lines displayed a remarkable bystander effect. As spheroids, the same six cell lines were sensitive to IFNβ gene transfer, two displaying a significant multicell resistance phenotype.The effects of conditioned IFNβ-lipofected canine melanoma cell culture media suggested the release of at least one soluble thermolabile cytotoxic factor that could not be detected in human melanoma cells. By using a secretion signal-free truncated human IFNβ, we showed that its intracellular expression was enough to induce cytotoxicity in two human melanoma cell lines. The lower cytoplasmatic levels of reactive oxygen species detected after intracellular IFNβ expression could be related to the resistance displayed by one human melanoma cell line. As IFNβ gene transfer was effective against most of the assayed melanomas in a way not limited by relatively low lipofection efficiencies, the clinical potential of this approach is strongly supported.Fil: Rossi, Ursula Amaranta. Universidad de Buenos Aires. Facultad de Medicina. Instituto de Oncología ; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Gil Cardeza, Maria Lourdes. Universidad de Buenos Aires. Facultad de Medicina. Instituto de Oncología ; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Villaverde, Marcela Solange. Universidad de Buenos Aires. Facultad de Medicina. Instituto de Oncología ; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Finocchiaro, Liliana Maria Elena. Universidad de Buenos Aires. Facultad de Medicina. Instituto de Oncología ; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Glikin, Gerardo Claudio. Universidad de Buenos Aires. Facultad de Medicina. Instituto de Oncología ; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin
Gauge and Scheme Dependence of Mixing Matrix Renormalization
We revisit the issue of mixing matrix renormalization in theories that
include Dirac or Majorana fermions. We show how a gauge-variant on-shell
renormalized mixing matrix can be related to a manifestly gauge-independent one
within a generalized scheme of renormalization. This
scheme-dependent relation is a consequence of the fact that in any scheme of
renormalization, the gauge-dependent part of the mixing-matrix counterterm is
ultra-violet safe and has a pure dispersive form. Employing the unitarity
properties of the theory, we can successfully utilize the afore-mentioned
scheme-dependent relation to preserve basic global or local symmetries of the
bare Lagrangian through the entire process of renormalization. As an immediate
application of our study, we derive the gauge-independent renormalization-group
equations of mixing matrices in a minimal extension of the Standard Model with
isosinglet neutrinos.Comment: 31 pages, LaTeX, uses axodraw.st
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