136 research outputs found
Charge Orbits of Symmetric Special Geometries and Attractors
We study the critical points of the black hole scalar potential in
N=2, d=4 supergravity coupled to vector multiplets, in an
asymptotically flat extremal black hole background described by a
2(n_{V}+1)-dimensional dyonic charge vector and (complex) scalar fields which
are coordinates of a special K\"{a}hler manifold.
For the case of homogeneous symmetric spaces, we find three general classes
of regular attractor solutions with non-vanishing Bekenstein-Hawking entropy.
They correspond to three (inequivalent) classes of orbits of the charge vector,
which is in a 2(n_{V}+1)-dimensional representation of the U-duality
group. Such orbits are non-degenerate, namely they have non-vanishing quartic
invariant (for rank-3 spaces). Other than the 1/2-BPS one, there are two other
distinct non-BPS classes of charge orbits, one of which has vanishing central
charge.
The three species of solutions to the N=2 extremal black hole attractor
equations give rise to different mass spectra of the scalar fluctuations, whose
pattern can be inferred by using invariance properties of the critical points
of and some group theoretical considerations on homogeneous symmetric
special K\"{a}hler geometry.Comment: 63 pages, 9 Tables. v2: typos fixed, Refs. added, accepted for
publication in IJMP
Public perception of nanotechnology
While several studies on the public opinion of nanotechnology have pointed to a rather enthusiastic U.S. public, the public uptake of nanotechnology in Europe is more contained. The results of the Swiss publifocus on nanotechnology reveal a pragmatic attitude of citizens toward the emerging technologies, thus confirming what has been identified as a "balanced approach” in the NanoJury U
Attractor Horizon Geometries of Extremal Black Holes
We report on recent advances in the study of critical points of the ``black hole effective potential'' V_{BH} (usually named \textit{attractors}) of N=2, d=4 supergravity coupled to n_{V} Abelian vector multiplets, in an asymptotically flat extremal black hole background described by 2n_{V}+2 dyonic charges and (complex) scalar fields which are coordinates of an n_{V}-dimensional Special Kahler manifold
Intersecting Attractors
We apply the entropy formalism to the study of the near-horizon geometry of
extremal black p-brane intersections in D>5 dimensional supergravities. The
scalar flow towards the horizon is described in terms an effective potential
given by the superposition of the kinetic energies of all the forms under which
the brane is charged. At the horizon active scalars get fixed to the minima of
the effective potential and the entropy function is given in terms of U-duality
invariants built entirely out of the black p-brane charges. The resulting
entropy function reproduces the central charges of the dual boundary CFT and
gives rise to a Bekenstein-Hawking like area law. The results are illustrated
in the case of black holes and black string intersections in D=6, 7, 8
supergravities where the effective potentials, attractor equations, moduli
spaces and entropy/central charges are worked out in full detail.Comment: 1+41 pages, 2 Table
Accumulation of Mutated Maize Zeins in Transgenic Forage Legumes
Accumulation of zeins, the endosperm storage proteins of maize, in a heterologous plant expression system was attempted. Plants of birdsfoot trefoil (Lotus corniculatus) and alfalfa (Medicago sativa) were transformed by Agrobacterium with binary vectors harboring genes that code for γ-zein and β-zein, two proteins rich in sulphur amino acids. Adding the ER retention signal KDEL to the C-terminal domain modified zein polypeptides. Our long-term goal was to improve birdsfoot trefoil and alfalfa forage quality. Significant levels of γ- zein:KDEL and β-zein:KDEL were detected in primary transformants of birdsfoot trefoil. Moreover, alfalfa plants expressing γ-zein:KDEL in the leaves were obtained. γ-zein:KDEL accumulated in spherical or elliptical electron-dense bodies of birdsfoot trefoil leaves. The protein bodies were present in the cytoplasm of either mesophyll cells or epidermis cells
Mirror Fermat Calabi-Yau Threefolds and Landau-Ginzburg Black Hole Attractors
We study black hole attractor equations for one-(complex structure)modulus Calabi-Yau spaces which are the mirror dual of Fermat Calabi-Yau threefolds (CY_{3}s). When exploring non-degenerate solutions near the Landau-Ginzburg point of the moduli space of such 4-dimensional compactifications, we always find two species of extremal black hole attractors, depending on the choice of the Sp(4,Z) symplectic charge vector, one 1/2-BPS (which is always stable, according to general results of special Kahler geometry) and one non-BPS. The latter turns out to be stable (local minimum of the ``effective black hole potential'' V_{BH}) for non-vanishing central charge, whereas it is unstable (saddle point of V_{BH}) for the case of vanishing central charge. This is to be compared to the large volume limit of one-modulus CY_{3}-compactifications (of Type II A superstrings), in which the homogeneous symmetric special Kahler geometry based on cubic prepotential admits (beside the 1/2-BPS ones) only non-BPS extremal black hole attractors with non-vanishing central charge, which are always stable.We study black hole attractor equations for one-(complex structure)modulus Calabi-Yau spaces which are the mirror dual of Fermat Calabi-Yau threefolds (CY_{3}s). When exploring non-degenerate solutions near the Landau-Ginzburg point of the moduli space of such 4-dimensional compactifications, we always find two species of extremal black hole attractors, depending on the choice of the Sp(4,Z) symplectic charge vector, one 1/2-BPS (which is always stable, according to general results of special Kahler geometry) and one non-BPS. The latter turns out to be stable (local minimum of the ``effective black hole potential'' V_{BH}) for non-vanishing central charge, whereas it is unstable (saddle point of V_{BH}) for the case of vanishing central charge. This is to be compared to the large volume limit of one-modulus CY_{3}-compactifications (of Type II A superstrings), in which the homogeneous symmetric special Kahler geometry based on cubic prepotential admits (beside the 1/2-BPS ones) only non-BPS extremal black hole attractors with non-vanishing central charge, which are always stable.We study black hole attractor equations for one-(complex structure)modulus Calabi-Yau spaces which are the mirror dual of Fermat Calabi-Yau threefolds (CY_{3}s). When exploring non-degenerate solutions near the Landau-Ginzburg point of the moduli space of such 4-dimensional compactifications, we always find two species of extremal black hole attractors, depending on the choice of the Sp(4,Z) symplectic charge vector, one 1/2-BPS (which is always stable, according to general results of special Kahler geometry) and one non-BPS. The latter turns out to be stable (local minimum of the ``effective black hole potential'' V_{BH}) for non-vanishing central charge, whereas it is unstable (saddle point of V_{BH}) for the case of vanishing central charge. This is to be compared to the large volume limit of one-modulus CY_{3}-compactifications (of Type II A superstrings), in which the homogeneous symmetric special Kahler geometry based on cubic prepotential admits (beside the 1/2-BPS ones) only non-BPS extremal black hole attractors with non-vanishing central charge, which are always stable.We discuss the “attractor mechanism” for extremal black-holes (BHs) in the context of Maxwell-Einstein supergravity theories. The BH squared mass at the horizon (related to the Bekenstein-Hawking entropy area formula) is determined by the “fixed points” of the so-called “BH potential”. In the considered framework, the scalar fields describe trajectories ending into such fixed points, which only depend on the electric and magnetic BH charges. Thus, the BH appears as a soliton, interpolating between maximally supersymmetric limiting solutions at spatial infinity and at the horizon. The BH entropy depend only on the BH charges, and it is independent of the initial data, i.e. on the values of the scalar fields at spatial infinity. In the considered theories, extremal BHs seem to behave as dynamical systems with fixed points (“attractors”) describing the thermodynamical equilibrium and stability features. An introductory review of the “special Kahler” geometry for scalar manifolds encompassing the BH background is given. A detailed study of the BH attractor equations for one-(complex structure)modulus Calabi-Yau spaces which are the mirror dual of Fermat Calabi-Yau threefolds (CY’s) is carried out as well. When exploring non-degenerate solutions near the Landau-Ginzburg point of the moduli space of such 4-dimensional compactifications, we always find two species of extremal black-hole attractors, depending on the choice of the Sp(4, ℤ) symplectic charge vector, one -BPS (which is always stable, according to general results of special Kahler geometry) and one non-BPS. The latter turns out to be stable (local minimum of the “effective black-hole potential” V) for non-vanishing central charge, whereas it is unstable (saddle point of V) for the case of vanishing central charge. This is to be compared to the large volume limit of one-modulus CY-compactifications (of type-IIA superstrings), in which the homogeneous symmetric special Kahler geometry based on cubic prepotential admits (beside the -BPS ones) only non-BPS extremal black-hole attractors with non-vanishing central charge, which are always stable
d=4 Black Hole Attractors in N=2 Supergravity with Fayet-Iliopoulos Terms
We generalize the description of the d=4 Attractor Mechanism based on an
effective black hole (BH) potential to the presence of a gauging which does not
modify the derivatives of the scalars and does not involve hypermultiplets. The
obtained results do not rely necessarily on supersymmetry, and they can be
extended to d>4, as well. Thence, we work out the example of the stu model of
N=2 supergravity in the presence of Fayet-Iliopoulos terms, for the
supergravity analogues of the magnetic and D0-D6 BH charge configurations, and
in three different symplectic frames: the SO(1,1)^{2}, SO(2,2) covariant and
SO(8)-truncated ones. The attractive nature of the critical points, related to
the semi-positive definiteness of the Hessian matrix, is also studied.Comment: 1+33 page
Orbits and Attractors for N=2 Maxwell-Einstein Supergravity Theories in Five Dimensions
BPS and non-BPS orbits for extremal black-holes in N=2 Maxwell-Einstein
supergravity theories (MESGT) in five dimensions were classified long ago by
the present authors for the case of symmetric scalar manifolds. Motivated by
these results and some recent work on non-supersymmetric attractors we show
that attractor equations in N=2 MESGTs in d=5 do indeed possess the distinct
families of solutions with finite Bekenstein-Hawking entropy. The new non-BPS
solutions have non-vanishing central charge and matter charge which is
invariant under the maximal compact subgroup of the stabilizer of the non-BPS
orbit. Our analysis covers all symmetric space theories G/H such that G is a
symmetry of the action. These theories are in one-to-one correspondence with
(Euclidean) Jordan algebras of degree three. In the particular case of N=2
MESGT with scalar manifold SU*(6)/USp(6) a duality of the two solutions with
regard to N=2 and N=6 supergravity is also considered.Comment: Added a footnote on notation and comments on the attactor nature of
non BPS solutions in section 5. Typos corrected. Version to appear in NPB.
Latex file, 24 page
Load bearing capability of three-units 4Y-TZP monolithic fixed dental prostheses: An innovative model for reliable testing
In this work, three-units monolithic fixed dental prostheses (FDPs) have been analysed and a novel model for reliable testing has been proposed. Such model is based on a new design of the polymeric base of the FDP, realised via additive manufacturing (AM) - a solution that conveys at the same time quick manufacturability, low cost, custom-ability, and design freedom. By means of this new model, the load-bearing capability of three-units monolithic FDPs has been thoroughly tested; in particular, three different analyses were performed: (i) analytical with a beam-like model, (ii) numerical, using non-linear three-dimensional Finite Elements (FE) models and (iii) experimental, by static bending test. The FDPs considered in this work were manufactured using a fourth-generation zirconia, namely 4Y-TZP. The findings
demonstrated the undoubted advantages of the new base configuration, which minimized the effect of the base (which as a matter of fact is absent in in-vivo conditions) on the stress state of the connectors in the FDPs, and increased the repeatability and reliability of the experimental bending tests, able to determine the load bearing capability of the 4Y-TZP FDPs
On the Moduli Space of non-BPS Attractors for N=2 Symmetric Manifolds
We study the ``flat'' directions of non-BPS extremal black hole attractors
for N=2, d=4 supergravities whose vector multiplets' scalar manifold is endowed
with homogeneous symmetric special Kahler geometry. The non-BPS attractors with
non-vanishing central charge have a moduli space described by real special
geometry (and thus related to the d=5 parent theory), whereas the moduli spaces
of non-BPS attractors with vanishing central charge are certain Kahler
homogeneous symmetric manifolds. The moduli spaces of the non-BPS attractors of
the corresponding N=2, d=5 theories are also indicated, and shown to be rank-1
homogeneous symmetric manifolds.Comment: 1+11 pages, 4 Table
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