323 research outputs found
TFD Extension of Open String Field Theory
We study the application of the rules of Thermo Field Dynamics (TFD) to the
covariant formulation of Open String Field Theory (OSFT). We extend the states
space and fields according to the duplication rules of TFD and construct the
corresponding classical action. The result is interpreted as a theory whose
fields would encode the statistical information of open strings.
The physical spectrum of the free theory is studied through the cohomology of
the extended BRST charge, and, as a result, we get new fields in the spectrum
emerging by virtue of the quantum entanglement and, noticeably, it presents
degrees of freedom that could be identified as those of closed strings. We also
show, however, that their appearing in the action is directly related to the
choice of the inner product in the extended algebra, so that different sectors
of fields could be eliminated from the theory by choosing that product
conveniently.
Finally, we study the extension of the three-vertex interaction and provide a
simple prescription for it whose results at tree-level agree with those of the
conventional theory.Comment: 25 pages, no figures. File format, typos, Abstract and references
modified. New subsection and concluding comments were added. To appear in
Phys. Rev.
Spectral properties of ghost Neumann matrices
We continue the analysis of the ghost wedge states in the oscillator
formalism by studying the spectral properties of the ghost matrices of Neumann
coefficients. We show that the traditional spectral representation is not valid
for these matrices and propose a new heuristic formula that allows one to
reconstruct them from the knowledge of their eigenvalues and eigenvectors. It
turns out that additional data, which we call boundary data, are needed in
order to actually implement the reconstruction. In particular our result lends
support to the conjecture that there exists a ghost three strings vertex with
properties parallel to those of the matter three strings vertex.Comment: 29 page
Thermofield dynamics extension of the open string field theory
We study the application of the rules of thermofield dynamics (TFD) to the covariant formulation of open-string field theory. We extend the states space and fields according to the duplication rules of TFD and construct the corresponding classical action. The result is interpreted as a theory whose fields would encode the statistical information of open strings. The physical spectrum of the free theory is studied through the cohomology of the extended Becchi, Rouet, Stora and Tyutin (BRST) charge, and, as a result, we get new fields in the spectrum emerging by virtue of the quantum entanglement, and, noticeably, it presents degrees of freedom that could be identified as those of closed strings. We also show, however, that their appearing in the action is directly related to the choice of the inner product in the extended algebra, so that different sectors of fields could be eliminated from the theory by choosing that product conveniently. Finally, we study the extension of the three-vertex interaction and provide a simple prescription for it of which the results at tree level agree with those of the conventional theory.Instituto de Física La Plat
Light-cone Superstring Field Theory, pp-wave background and integrability properties
We show that the three strings vertex coefficients in light--cone open string
field theory satisfy the Hirota equations for the dispersionless Toda lattice
hierarchy. We show that Hirota equations allow us to calculate the correlators
of an associated quantum system where the Neumann coefficients represent the
two--point functions. We consider next the three strings vertex coefficients of
the light--cone string field theory on a maximally supersymmetric pp--wave
background. Using the previous results we are able to show that these Neumann
coefficients satisfy the Hirota equations for the full Toda lattice hierarchy
at least up to second order in the 'string mass' .Comment: 23 pages, 3 figures, footnote and references adde
Time-localized projectors in String Field Theory with E-field
We extend the analysis of hep-th/0409063 to the case of a constant electric
field turned on the worldvolume and on a transverse direction of a D-brane. We
show that time localization is still obtained by inverting the discrete
eigenvalues of the lump solution. The lifetime of the unstable soliton is shown
to depend on two free parameters: the b-parameter and the value of the electric
field. As a by-product, we construct the normalized diagonal basis of the star
algebra in -field background.Comment: 27 +1 pages, v2: references added, typos correcte
Produtividade e características agronômicas de genótipo de milheto em quatro idades de corte.
Objetivou-se avaliar a produtividade e as características agronômicas do genótipo de milheto IPA BULK 1 BF cortado em quatro idades, visando à produção de silagem, em condições semiáridas
Habitable Zones in the Universe
Habitability varies dramatically with location and time in the universe. This
was recognized centuries ago, but it was only in the last few decades that
astronomers began to systematize the study of habitability. The introduction of
the concept of the habitable zone was key to progress in this area. The
habitable zone concept was first applied to the space around a star, now called
the Circumstellar Habitable Zone. Recently, other, vastly broader, habitable
zones have been proposed. We review the historical development of the concept
of habitable zones and the present state of the research. We also suggest ways
to make progress on each of the habitable zones and to unify them into a single
concept encompassing the entire universe.Comment: 71 pages, 3 figures, 1 table; to be published in Origins of Life and
Evolution of Biospheres; table slightly revise
TRY plant trait database - enhanced coverage and open access
Plant traits-the morphological, anatomical, physiological, biochemical and phenological characteristics of plants-determine how plants respond to environmental factors, affect other trophic levels, and influence ecosystem properties and their benefits and detriments to people. Plant trait data thus represent the basis for a vast area of research spanning from evolutionary biology, community and functional ecology, to biodiversity conservation, ecosystem and landscape management, restoration, biogeography and earth system modelling. Since its foundation in 2007, the TRY database of plant traits has grown continuously. It now provides unprecedented data coverage under an open access data policy and is the main plant trait database used by the research community worldwide. Increasingly, the TRY database also supports new frontiers of trait-based plant research, including the identification of data gaps and the subsequent mobilization or measurement of new data. To support this development, in this article we evaluate the extent of the trait data compiled in TRY and analyse emerging patterns of data coverage and representativeness. Best species coverage is achieved for categorical traits-almost complete coverage for 'plant growth form'. However, most traits relevant for ecology and vegetation modelling are characterized by continuous intraspecific variation and trait-environmental relationships. These traits have to be measured on individual plants in their respective environment. Despite unprecedented data coverage, we observe a humbling lack of completeness and representativeness of these continuous traits in many aspects. We, therefore, conclude that reducing data gaps and biases in the TRY database remains a key challenge and requires a coordinated approach to data mobilization and trait measurements. This can only be achieved in collaboration with other initiatives
Harnessing Wicked Problems in Multi-stakeholder Partnerships
Despite the burgeoning literature on the governance and impact of cross-sector partnerships in the past two decades, the debate on how and when these collaborative arrangements address globally relevant problems and contribute to systemic
change remains open. Building upon the notion of wicked problems and the literature on governing such wicked problems, this paper defines
harnessing problems in multi-stakeholder partnerships (MSPs) as the approach of taking into account the nature of the problem and of organizing governance processes accordingly. The paper develops an innovative analytical framework that conceptualizes MSPs in terms of three governance processes (deliberation, decision-making and enforce-ment) harnessing three key dimensions of wicked problems (knowledge uncertainty, value conflict and dynamic complexity).
The Roundtable on Sustainable Palm Oil provides an illustrative case study on how this analytical framework describes and explains organizational change in partnerships from a problem-based perspective. The framework can be used to better understand and predict the complex relationships between MSP governance processes, systemic change and societal problems, but also as a guiding tool in (re-)organizing governance processes to continuously re-assess the problems over time and address them accordingly
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