495 research outputs found
Goldstone models in D+1 dimensions, D=3,4,5, supporting stable and zero topological charge solutions
We study finite energy static solutions to a global symmetry breaking
Goldstone model described by an isovector scalar field in D+1 spacetime
dimensions. Both topologically stable multisolitons with arbitrary winding
numbers, and zero topological charge soliton--antisoliton solutions are
constructed numerically in D=3,4,5. We have explored the types of symmetries
the systems should be subjected to, for there to exist multisoliton and
soliton--antisoliton pairs in D=3,4,5,6. These findings are underpinned by
constructing numerical solutions in the examples. Subject to axial
symmetry, only multisolitons of all topological charges exist in even D, and in
odd D, only zero and unit topological charge solutions exist. Subjecting the
system to weaker than axial symmetries, results in the existence of all the
possibilities in all dimensions. Our findings apply also to finite 'energy'
solutions to Yang--Mills and Yang-Mills--Higgs systems, and in principle also
sigma models.Comment: 29 pages, 6 figure
Rotating nonuniform black string solutions
We explore via linearized perturbation theory the Gregory-Laflamme
instability of rotating black strings with equal magnitude angular momenta. Our
results indicate that the Gregory-Laflamme instability persists up to
extremality for all even dimensions between six and fourteen. We construct
rotating nonuniform black strings with two equal magnitude angular momenta in
six dimensions. We see a first indication for the occurrence of a topology
changing transition, associated with such rotating nonuniform black strings.
Charged nonuniform black string configurations in heterotic string theory are
also constructed by employing a solution generation technique.Comment: 36 pages, 10 figures, final versio
New stable phase of non uniform black strings in
We consider the non uniform black string equations in arbitrary number
of dimension in a perturbative approach up to order 2 and in a non
perturbative. We restrict the study in the perturbative approach to the
backreacting modes, since they provide the first relevant corrections on the
thermodynamical quantities of the solutions. We also present some preliminary
results in the construction of non-perturbative solutions, in particular, we
present a first part of the non uniform - uniform black string phase diagram.
Our results suggests the existence of a new stable phase for non uniform
black strings, namely long non uniform black string, with the extra direction
length of the order of the curvature.Comment: Results extended. 14 pages, 5 figure
New nonuniform black string solutions
We present nonuniform vacuum black strings in five and six spacetime
dimensions. The conserved charges and the action of these solutions are
computed by employing a quasilocal formalism. We find qualitative agreement of
the physical properties of nonuniform black strings in five and six dimensions.
Our results offer further evidence that the black hole and the black string
branches merge at a topology changing transition. We generate black string
solutions of the Einstein-Maxwell-dilaton theory by using a Harrison
transformation. We argue that the basic features of these solutions can be
derived from those of the vacuum black string configurations.Comment: 30 pages, 12 figures; v2: more details on numerical method,
references added; v3: references added, minor revisions, version accepted by
journa
Harrison transformation and charged black objects in Kaluza-Klein theory
We generate charged black brane solutions in dimensions in a theory of
gravity coupled to a dilaton and an antisymmetric form, by using a
Harrison-type transformation. The seed vacuum solutions that we use correspond
to uplifted Kaluza-Klein black strings and black holes in -dimensions. A
generalization of the Marolf-Mann quasilocal formalism to the Kaluza-Klein
theory is also presented, the global charges of the black objects being
computed in this way. We argue that the thermodynamics of the charged solutions
can be derived from that of the vacuum configurations. Our results show that
all charged Kaluza-Klein solutions constructed by means of Harrison
transformations are thermodynamically unstable in a grand canonical ensemble.
The general formalism is applied to the case of nonuniform black strings and
caged black hole solutions in Einstein-Maxwell-dilaton gravity, whose
geometrical properties and thermodynamics are discussed. We argue that the
topology changing transition scenario, which was previously proposed in the
vacuum case, also holds in this case. Spinning generalizations of the charged
black strings are constructed in six dimensions in the slowly rotating limit.
We find that the gyromagnetic ratio of these solutions possesses a nontrivial
dependence on the nonuniformity parameter.Comment: 42 pages, 12 figure
Transcriptional and Epigenetic Regulation of Effector and Memory CD8 T Cell Differentiation
Immune protection and lasting memory are accomplished through the generation of phenotypically and functionally distinct CD8 T cell subsets. Understanding how these effector and memory T cells are formed is the first step in eventually manipulating the immune system for therapeutic benefit. In this review, we will summarize the current understanding of CD8 T cell differentiation upon acute infection, with a focus on the transcriptional and epigenetic regulation of cell fate decision and memory formation. Moreover, we will highlight the importance of high throughput sequencing approaches and single cell technologies in providing insight into genome-wide investigations and the heterogeneity of individual CD8 T cells
Sunscreens - Which and what for?
It is well established that sun exposure is the main cause for the development of skin cancer. Chronic continuous UV radiation is believed to induce malignant melanoma, whereas intermittent high-dose UV exposure contributes to the occurrence of actinic keratosis as precursor lesions of squamous cell carcinoma as well as basal cell carcinoma. Not only photocarcinogenesis but also the mechanisms of photoaging have recently become apparent. In this respect the use of sunscreens seemed to prove to be more and more important and popular within the last decades. However, there is still inconsistency about the usefulness of sunscreens. Several studies show that inadequate use and incomplete UV spectrum efficacy may compromise protection more than previously expected. The sunscreen market is crowded by numerous products. Inorganic sunscreens such as zinc oxide and titanium oxide have a wide spectral range of activity compared to most of the organic sunscreen products. It is not uncommon for organic sunscreens to cause photocontact allergy, but their cosmetic acceptability is still superior to the one given by inorganic sunscreens. Recently, modern galenic approaches such as micronization and encapsulation allow the development of high-quality inorganic sunscreens. The potential systemic toxicity of organic sunscreens has lately primarily been discussed controversially in public, and several studies show contradictory results. Although a matter of debate, at present the sun protection factor (SPF) is the most reliable information for the consumer as a measure of sunscreen filter efficacy. In this context additional tests have been introduced for the evaluation of not only the protective effect against erythema but also protection against UV-induced immunological and mutational effects. Recently, combinations of UV filters with agents active in DNA repair have been introduced in order to improve photoprotection. This article reviews the efficacy of sunscreens in the prevention of epithelial and nonepithelial skin cancer, the effect on immunosuppression and the value of the SPF as well as new developments on the sunscreen market. Copyright (C) 2005 S. Karger AG, Basel
What can food service operators do to remedy undernutrition in hospitals? – a European perspective from an ad hoc group on Nutrition Programmes in Hospitals
Second-order -regularity in nonlinear elliptic problems
A second-order regularity theory is developed for solutions to a class of
quasilinear elliptic equations in divergence form, including the -Laplace
equation, with merely square-integrable right-hand side. Our results amount to
the existence and square integrability of the weak derivatives of the nonlinear
expression of the gradient under the divergence operator. This provides a
nonlinear counterpart of the classical -coercivity theory for linear
problems, which is missing in the existing literature. Both local and global
estimates are established. The latter apply to solutions to either Dirichlet or
Neumann boundary value problems. Minimal regularity on the boundary of the
domain is required. If the domain is convex, no regularity of its boundary is
needed at all
- …