1,721,001 research outputs found
D-branes on C^3_6. Part I: prepotential and GW-invariants
Full text linkThis is the first of a set of papers having the aim to provide a detailed description of brane configurations on a family of noncompact threedimensional Calabi-Yau manifolds. The starting point is the singular manifold C^3/Z_6, which admits five distinct crepant resolutions. Here we apply local mirror symmetry to partially determine the prepotential encoding the GW-invariants of the resolved varieties. It results that such prepotential provides all numbers but the ones corresponding to curves having null intersection with the compact divisor. This is realized by means of a conjecture, due to S. Hosono, so that our results provide a check confirming at least in part the conjecture
On the geometry of C^3/\Delta_{27} and del Pezzo surfaces
Full text linkWe clarify some aspects of the geometry of a resolution of the orbifold X = C3/Δ27, the noncompact complex manifold underlying the brane quiver standard model recently proposed by Verlinde and Wijnholt. We explicitly realize a map between X and the total space of the canonical bundle over a degree 1 quasi del Pezzo surface, thus defining a desingularization of X. Our analysis relys essentially on the relationship existing between the normalizer group of Δ27 and the Hessian group and on the study of the behaviour of the Hesse pencil of plane cubic curves under the quotient
Quantum instability for charged scalar articles on charged Nariai and ultracold black hole manifolds
No full textWe analyze in detail the quantum instability which characterizes charged scalar
field on three special de Sitter charged black hole backgrounds. In particular,
we compute exactly the imaginary part of the effective action for scalar charged
fields on the ultracold I, ultracold II and Nariai charged black hole backgrounds.
Both the transmission coefficient approach and the zeta-function approach are
exploited. Thermal effects on this quantum instability are also taken into
account in the presence of a non-zero black hole temperature (ultracold I and
Nariai)
Quantum instability for charged particles on charged Nariai black hole manifolds: Exact 4D results for black hole discharge phenomenon
No full textSupersymmetric Standard Model, Branes and Del Pezzo Surfaces
No full textThe Standard Model of particle physics is one of the most important successful results of the work of the last century physicists. In this new book, the authors present topical research in the study of new developments in the Standard Model. Topics discussed include non-equilibrium theory, fractional dynamics and the physics of the terascale sector; unexplored regions in QFT and the conceptual foundations of the Standard Model; supersymmetric Standard Model, Branes and Del Pezzo surfaces; fermion condensate as Higgs substitute and Lepton flavor violation shedding light on CP-violation.
Even though the Standard Model of particles has been confirme by several experiments, many questions require improvements. Beyond the problem of Grand Unification the mass gap problem, the question of hierarchies, low boson masses and dynamical soft supersymmetry breaking, there is the really hard difficult in including gravity in a full quantum paradigm of the Standard Model. The most famous scheme elaborated in order to solve the last and, possibly, all this points is String Theory.
Dualities, mirror symmetry, M-theory and AdS/CFT are some of the powerful tools
which permit to perform several progresses in all the mentioned directions, at least in principle. However, interactions of String Theory with phenomenology are really recent results. A way to get a contact between theory and phenomenology is the so called bottom-up approach. We will present here a possible String Theory approach to the (Minimal Supersymmetric) Standard Model based on the geometric engineering construction firs proposed in [H. Verlinde and M. Wijnholt, JHEP 0701, 106]. We will study the relevant geometry along the lines of [S.L. Cacciatori and M. Compagnoni, JHEP 1005:078,2010], and the related physics. We will study the singular orbifold C3/27, with 27 a suitable non abelian group, its geometry and show how it can be desingularized. To render technical computations as simple as possible we will work also with a simplifie toric version, studing its main properties at K-theory level, and we will discuss how such calculations should be extended to the non abelian case. The associated relevant physics will be discussed
General symmetries: from homogeneous thermodynamics to black holes
No full textWe consider the topic of symmetries as classifying tools for thermodynamic systems. We adopt the contact geometry approach, in a general framework including standard homogeneous thermodynamics but not limited to it, and we focus our attention on the problem of the existence of a general symmetry, to
be defined as a symmetry which is the same for a class of thermodynamic systems. Homogeneity symmetry of standard equilibrium thermodynamics is the paradigmatic example of general symmetry, and we point out its being associated with a multi-class thermodynamics, whose mathematical characterization is taken into account. Furthermore, quasi-homogeneity symmetry, which describes some non-extensive systems, is shown to give rise to a general symmetry, in the above sense, in the case of non-relativistic self-gravitating fermions. In the latter case, it is also conjectured to give rise to a multi-class structure. An analysis of the behavior of transversal symmetries under the partial Legendre involutions enhances a special role of quasi-homogeneity symmetry, as well as the role of special thermodynamic limit is pointed out as a tool for investigating the topic of general symmetries
The Dirac equation in Kerr-Newman-AdS black hole background
No full textWe consider the Dirac equation on the Kerr–Newman–AdS black hole background. We first perform the variable separation for the Dirac equation and define the Hamiltonian operator H. Then we show that for a massive Dirac field with mass \mu \geq 1 / ͑(2l), where l is linked to the cosmological constant \Lambda by \Lambda = -3 /(l^2), essential self-adjointness of H on
C_0^\infty ((r_+ ,\infty)\times S^2͒)^4 is obtained even in presence of the boundarylike behavior of infinity in an asymptotically AdS black hole background. Furthermore, qualitative spectral properties of the Hamiltonian are taken into account and in agreement with the existing results concerning the case of stationary axisymmetric asymptotically flat black holes we infer the absence of time-periodic and normalizable solutions of the Dirac equation around the black hole in the nonextremal case
Absence of normalizable time-periodic solutions for the Dirac equation in Kerr Newman-dS black hole background
No full textWe consider the Dirac equation on the background of a Kerr–Newman–de
Sitter black hole. By performing variable separation, we show that no time-
periodic and normalizable solution of the Dirac equation is allowed, which
amounts to the absence of quantum bound states for the Dirac Hamiltonian.
This conclusion holds true even for extremal black holes. With respect to
previously considered cases, the novelty is represented by the presence, in
addition to a black hole event horizon, of a cosmological (non-degenerate)
event horizon, which is at the root of the possibility to draw a conclusion on
the aforementioned topic in a straightforward way even in the extremal case
Massive Dirac particles on the background of charged de Sitter black hole manifolds
No full textWe consider the behavior of massive Dirac fields on the background of a charged de Sitter black hole. All black hole geometries are taken into account, including the Reissner-Nordstrom-de Sitter one, the Nariai case, and the ultracold case. Our focus is at first on the existence of bound quantum mechanical states for the Dirac Hamiltonian on the given backgrounds. In this respect, we show that in all cases no bound state is allowed, which amounts also to the nonexistence of normalizable time-periodic solutions of the Dirac equation. This quantum result is in contrast to classical physics, and it is shown to hold true even for extremal cases. Furthermore, we shift our attention on the very interesting problem of the quantum discharge of the black holes. Following the Damour-Deruelle-Ruffini approach, we show that the existence of level crossing between positive and negative continuous energy states is a signal of the
quantum instability leading to the discharge of the black hole, and in the cases of the Nariai geometry and of the ultracold geometries we also calculate in WKB approximation the transmission coefficient related to the discharge process
Quantum Effects for the Dirac Field in Reissner-Nordstrom-AdS Black Hole Background
No full textThe behavior of a charged massive Dirac field on a Reissner–Nordstrom–AdS
black hole background is investigated. We first analyze the problem of the
essential self-adjointness of the Dirac Hamiltonian, which is made difficult by
the boundary-like behavior of spatial infinity, and we find that the Hamiltonian
is essentially self-adjoint iff \mu L \geq 1/2; moreover, we determine the essential
spectrum of the Hamiltonian. Then we focus on the analysis of the discharge
problem for the case \mu L \geq 1/2. We follow the Ruffini–Damour–Deruelle
approach and, as in the standard Reissner–Nordstrom black hole case, we
find that the existence of level-crossing between the positive and negative
energy solutions of the Dirac equation is at the root of the pair-creation process
associated with the discharge of the black hole
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