1. SupergeometrodynamicsMirjam Cvetič, G. W. Gibbons, Christopher N. Pope, 2015, izvirni znanstveni članek Opis: We present explicit solutions of the timesymmetric initial value constraints, expressed in terms of freely specifiable harmonic functions for examples of supergravity theories, which emerge as effective theories of compactified string theory. These results are a prerequisite for the study of the timeevolution of topologically nontrivial initial data for supergravity theories, thus generalising the "Geometrodynamics" program of EinsteinMaxwell theory to that of supergravity theories. Specifically, we focus on examples of multiple electric Maxwell and scalar fields, and analyse the initial data problem for the general EinsteinMaxwellDilaton theory both with one and two Maxwell fields, and the STU model. The solutions are given in terms of up to eight arbitrary harmonic functions in the STU model. As a byproduct, in order compare our results with known static solutions, the metric in isotropic coordinates and all the sources of the nonextremal black holes are expressed entirely in terms of harmonic functions. We also comment on generalizations to timenonsymmetric initial data and their relation to cosmological solutions of gauged socalled fake supergravities with positive cosmological constant. Ključne besede: black holes, supergravity, string theory, conformal field models, string duality Objavljeno: 14.06.2017; Ogledov: 202; Prenosov: 35 Celotno besedilo (581,40 KB) Gradivo ima več datotek! Več...

2. Entanglement entropy of subtracted geometry black holesMirjam Cvetič, Zain H. Saleem, Alejandro Satz, 2015, polemika, diskusijski prispevek, komentar Opis: We compute the entanglement entropy of minimally coupled scalar fields on subtracted geometry black hole backgrounds, focusing on the logarithmic corrections. We notice that matching between the entanglement entropy of original black holes and their subtracted counterparts is only at the order of the area term. The logarithmic correction term is not only different but also, in general, changes sign in the subtracted case. We apply Harrison transformations to the original black holes and find out the choice of the Harrison parameters for which the logarithmic corrections vanish. Ključne besede: black holes, string theory Objavljeno: 14.06.2017; Ogledov: 160; Prenosov: 98 Celotno besedilo (378,41 KB) Gradivo ima več datotek! Več...

3. AdS(2) holographic dictionaryMirjam Cvetič, Ioannis Papadimitriou, 2016, izvirni znanstveni članek Opis: We construct the holographic dictionary for both running and constant dilaton solutions of the two dimensional EinsteinMaxwellDilaton theory that is obtained by a circle reduction from EinsteinHilbert gravity with negative cosmological constant in three dimensions. This specific model ensures that the dual theory has a well de fined ultraviolet completion in terms of a two dimensional conformal field theory, but our results apply qualitatively to a wider class of two dimensional dilaton gravity theories. For each type of solutions we perform holographic renormalization, compute the exact renormalized onepoint functions in the presence of arbitrary sources, and derive the asymptotic symmetries and the corresponding conserved charges. In both cases we find that the scalar operator dual to the dilaton plays a crucial role in the description of the dynamics. Its source gives rise to a matter conformal anomaly for the running dilaton solutions, while its expectation value is the only non trivial observable for constant dilaton solutions. The role of this operator has been largely overlooked in the literature. We further show that the only non trivial conserved charges for running dilaton solutions are the mass and the electric charge, while for constant dilaton solutions only the electric charge is non zero. However, by uplifting the solutions to three dimensions we show that constant dilaton solutions can support non trivial extended symmetry algebras, including the one found by Comp ere, Song and Strominger [1], in agreement with the results of Castro and Song [2]. Finally, we demonstrate that any solution of this specific dilaton gravity model can be uplifted to a family of asymptotically AdS(2) x S2 or conformally AdS(2) x S2 solutions of the STU model in four dimensions, including non extremal black holes. The four dimensional solutions obtained by uplifting the running dilaton solutions coincide with the so called 'subtracted geometries', while those obtained from the uplift of the constant dilaton ones are new. Ključne besede: 2D gravity, AdSCFT correspondence, black holes, spacetime symmetries Objavljeno: 27.06.2017; Ogledov: 203; Prenosov: 78 Celotno besedilo (1,01 MB) Gradivo ima več datotek! Več...

4. Black hole thermodynamics from a variational principle: asymptotically conical backgroundsSongok An, Mirjam Cvetič, Ioannis Papadimitriou, 2016, izvirni znanstveni članek Opis: The variational problem of gravity theories is directly related to black hole thermodynamics. For asymptotically locally AdS backgrounds it is known that holographic renormalization results in a variational principle in terms of equivalence classes of boundary data under the local asymptotic symmetries of the theory, which automatically leads to finite conserved charges satisfying the first law of thermodynamics. We show that this connection holds well beyond asymptotically AdS black holes. In particular, we formulate the variational problem for N = 2 STU supergravity in four dimensions with boundary conditions corresponding to those obeyed by the so called 'subtracted geometries'. We show that such boundary conditions can be imposed covariantly in terms of a set of asymptotic second class constraints, and we derive the appropriate boundary terms that render the variational problem well posed in two different duality frames of the STU model. This allows us to define finite conserved charges associated with any asymptotic Killing vector and to demonstrate that these charges satisfy the Smarr formula and the first law of thermodynamics. Moreover, by uplifting the theory to five dimensions and then reducing on a 2sphere, we provide a precise map between the thermodynamic observables of the subtracted geometries and those of the BTZ black hole. Surface terms play a crucial role in this identification. Ključne besede: MTheory, Black Holes, String Theory, Gaugegravity correspondence Objavljeno: 27.06.2017; Ogledov: 221; Prenosov: 90 Celotno besedilo (834,82 KB) Gradivo ima več datotek! Več...

5. Black holes with intrinsic spinMirjam Cvetič, Finn Larsen, 2014, izvirni znanstveni članek Opis: We analyze the general black hole solutions to the four dimensional STU model recently constructed by Chow and Compere. We define a dilute gas limit where the black holes can be interpreted as excited states of an extremal ground state. In this limit we express the black hole entropy and the excitation energy in terms of physical quantities with no need for parametric charges. We discuss a dual microscopic CFT description that incorporates all electric and magnetic charges. This description is recovered geometrically by identification of a near horizon BTZ region. We construct the subtracted geometry with no restrictions on charges by analyzing the scalar wave equation in the full geometry. We determine the matter sources that support the subtracted geometry by studying a scaling limit and show that the general geometry permits a dilute gas description with parameters that we specify. Ključne besede: black holes, string theory, conformal field models, string duality Objavljeno: 27.06.2017; Ogledov: 240; Prenosov: 95 Celotno besedilo (598,59 KB) Gradivo ima več datotek! Več...

6. Electrodynamics of black holes in STU supergravityMirjam Cvetič, G. W. Gibbons, Christopher N. Pope, Zain H. Saleem, 2014, izvirni znanstveni članek Opis: External magnetic fields can probe the composite structure of black holes in string theory. With this motivation we study magnetised fourcharge black holes in the STU model, a consistent truncation of maximally supersymmetric supergravity with four types of electromagnetic fields. We employ solution generating techniques to obtain Melvin backgrounds, and black holes in these backgrounds. For an initially electrically charged static black hole immersed in magnetic fields, we calculate the resultant angular momenta and analyse their global structure. Examples are given for which the ergoregion does not extend to infinity. We calculate magnetic moments and gyromagnetic ratios via Larmor's formula. Our results are consistent with earlier special cases. A scaling limit and associated subtracted geometry in a single surviving magnetic field is shown to lift to AdS(3) x S2. Magnetizing magnetically charged black holes give static solutions with conical singularities representing strings or struts holding the black holes against magnetic forces. In some cases it is possible to balance these magnetic forces. Ključne besede: black holes, supergravity, string theory, conformal field models, string duality Objavljeno: 27.06.2017; Ogledov: 210; Prenosov: 101 Celotno besedilo (563,26 KB) Gradivo ima več datotek! Več...

7. On finiteness of type IIB compactificationsMirjam Cvetič, James Halverson, Denis Klevers, Peng Song, 2014, izvirni znanstveni članek Opis: The string landscape satisfies interesting finiteness properties imposed by supersymmetry and stringtheoretical consistency conditions. We study N = 1 supersymmetric compactifications of Type IIB string theory on smooth elliptically fibered CalabiYau threefolds at large volume with magnetized D9branes and D5branes. We prove that supersymmetry and tadpole cancellation conditions imply that there is a finite number of such configurations. In particular, we derive an explicitly computable bound on the number of magnetic flux quanta, as well as the number of D5branes, which is independent of the continuous moduli of the setup. The proof applies if a number of easy to check geometric conditions of the twofold base are met. We show that these geometric conditions are satisfied for the almost Fano twofold bases given by each toric variety associated to a reflexive twodimensional polytope as well as by the generic del Pezzo surfaces dP(n) with n = 0, ..., 8. Physically, this finiteness proof shows that there exist a finite collection of fourdimensional gauge groups and chiral matter spectra in the 4D supergravity theories realized by these compactifications. As a byproduct we explicitly construct all generators of the Kaahler cones of dP(n) and work out their relation to representation theory. Ključne besede: black holes, supergravity, string theory, conformal field models, string duality Objavljeno: 27.06.2017; Ogledov: 267; Prenosov: 36 Celotno besedilo (1,01 MB) Gradivo ima več datotek! Več...

8. Threefamily particle physics models from global Ftheory compactificationsMirjam Cvetič, Denis Klevers, Damian Kaloni Mayorga Pena, Paul Oehlmann, Jonas Reuter, 2015, izvirni znanstveni članek Opis: We construct fourdimensional, globally consistent Ftheory models with three chiral generations, whose gauge group and matter representations coincide with those of the Minimal Supersymmetric Standard Model, the PatiSalam Model and the Trinification Model. These models result from compactification on toric hypersurface fibrations X with the choice of base P3. We observe that the Ftheory conditions on the G(4)flux restrict the number of families to be at least three. We comment on the phenomenology of the models, and for PatiSalam and Trinification models discuss the Higgsing to the Standard Model. A central point of this work is the construction of globally consistent G(4)flux. For this purpose we compute the vertical cohomology HV((2,2)) (X) in each case and solve the conditions imposed by matching the M and Ftheoretical 3D ChernSimons terms. We explicitly check that the expressions found for the G(4)flux allow for a cancellation of D3brane tadpoles. We also use the integrality of 3D ChernSimons terms to ensure that our G(4)flux solutions are adequately quantized. Ključne besede: black holes, supergravity, string theory, conformal field models, string duality Objavljeno: 27.06.2017; Ogledov: 432; Prenosov: 88 Celotno besedilo (890,06 KB) Gradivo ima več datotek! Več...

9. Vacuum polarization of STU black holes and their subtracted geometry limitMirjam Cvetič, G. W. Gibbons, Zain H. Saleem, Alejandro Satz, 2015, izvirni znanstveni članek Opis: We study the vacuum polarization of a massless minimally coupled scalar field at the horizon of fourcharge STU black holes. We compare the results for the standard asymptotically flat black holes and for the black holes obtained in the "subtracted limit", both in the general static case and at the horizon pole for the general rotating case. The original and the subtracted results are identical only in the BPS limit, and have opposite sign in the extremal Kerr limit. We also compute the vacuum polarization on the static solutions that interpolate between both the original and the subtracted case through a solutiongenerating transformation and show that the vacuum polarization stays positive throughout the interpolating solution. In the appendix we provide a closedform solution for the Green's function on general (static or rotating) subtracted black hole geometries. Ključne besede: black holes, supergravity, string theory, conformal field models, string duality Objavljeno: 27.06.2017; Ogledov: 385; Prenosov: 75 Celotno besedilo (372,93 KB) Gradivo ima več datotek! Več...

10. Wave equation for the Wu black holeTolga Birkandan, Mirjam Cvetič, 2014, izvirni znanstveni članek Opis: Wu black hole is the most general solution of maximally supersymmetric gauged supergravity in D=5, containing U(1)(3) gauge symmetry. We study the separability of the massless KleinGordon equation and probe its singularities for a general stationary, axisymmetric metric with orthogonal transitivity, and apply the results to the Wu black hole solution. We start with the zero azimuthalangle eigenvalues in the scalar field Ansatz and find that the residuum of a pole in the radial equation is associated with the surface gravity calculated at this horizon. We then generalize our calculations to nonzero azimuthal eigenvalues and probing each horizon singularity, we show that the residua of the singularities for each horizon are in general associated with a specific combination of the surface gravity and the angular velocities at the associated horizon. It turns out that for the Wu black hole both the radial and angular equations are general Heun's equations with four regular singularities. Ključne besede: black holes, string theory, conformal field models, string duality Objavljeno: 27.06.2017; Ogledov: 432; Prenosov: 90 Celotno besedilo (424,79 KB) Gradivo ima več datotek! Več...
