11. 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: 77 Celotno besedilo (372,93 KB) Gradivo ima več datotek! Več...

12. 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: 90 Celotno besedilo (890,06 KB) Gradivo ima več datotek! Več...

13. Origin of Abelian gauge symmetries in heterotic/Ftheory dualityMirjam Cvetič, Antonella Grassi, Denis Klevers, Peng Song, Maximilian Poretschkin, 2016, izvirni znanstveni članek Opis: We study aspects of heterotic/Ftheory duality for compactifications with Abelian gauge symmetries. We consider Ftheory on general CalabiYau manifolds with a rank one MordellWeil group of rational sections. By rigorously performing the stable degeneration limit in a class of toric models, we derive both the CalabiYau geometry as well as the spectral cover describing the vector bundle in the heterotic dual theory. We carefully investigate the spectral cover employing the group law on the elliptic curve in the heterotic theory. We find in explicit examples that there are three different classes of heterotic duals that have U(1) factors in their low energy effective theories: split spectral covers describing bundles with S(U(m) x U(1)) structure group, spectral covers containing torsional sections that seem to give rise to bundles with SU(m) X Z(k) structure group and bundles with purely nonAbelian structure groups having a centralizer in E8 containing a U(1) factor. In the former two cases, it is required that the elliptic fibration on the heterotic side has a nontrivial MordellWeil group. While the number of geometrically massless U(1)'s is determined entirely by geometry on the Ftheory side, on the heterotic side the correct number of U(1)'s is found by taking into account a Stiickelberg mechanism in the lowerdimensional effective theory. In geometry, this corresponds to the condition that sections in the two half K3 surfaces that arise in the stable degeneration limit of Ftheory can be glued together globally. Ključne besede: Ftheory, string duality, superstrings, heterotic strings, Mtheory Objavljeno: 27.06.2017; Ogledov: 349; Prenosov: 99 Celotno besedilo (1,15 MB) Gradivo ima več datotek! Več...

14. 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: 268; Prenosov: 36 Celotno besedilo (1,01 MB) Gradivo ima več datotek! Več...

15. Elliptic fibrations with rank three MordellWeilgroupMirjam Cvetič, Denis Klevers, Hernan Piragua, Peng Song, 2014, izvirni znanstveni članek Opis: We analyze general Ftheory compactifications with U(1)xU(1)xU(1) Abelian gauge symmetry by constructing the general elliptically fibered CalabiYau manifolds with a rank three MordellWeil group of rational sections. The general elliptic fiber is shown to be a complete intersection of two nongeneric quadrics in P3 and resolved elliptic fibrations are obtained by embedding the fiber as the generic CalabiYau complete intersection into Bl(3)P(3), the blowup of P3 at three points. For a fixed base B, there are finitely many CalabiYau elliptic fibrations. Thus, Ftheory compactifications on these CalabiYau manifolds are shown to be labeled by integral points in reflexive polytopes constructed from the nefpartition of Bl(3)P(3). We determine all 14 massless matter representations to six and four dimensions by an explicit study of the codimension two singularities of the elliptic fibration. We obtain three matter representations charged under all three U(1)factors, most notably a trifundamental representation. The existence of these representations, which are not present in generic perturbative Type II compactifications, signifies an intriguing universal structure of codimension two singularities of the elliptic fibrations with higher rank MordellWeil groups. We also compute explicitly the corresponding 14 multiplicities of massless hypermultiplets of a sixdimensional Ftheory compactification for a general base B. Ključne besede: flux compactifications, Ftheory, superstring vacua, Dbranes Objavljeno: 27.06.2017; Ogledov: 202; Prenosov: 55 Celotno besedilo (840,88 KB) Gradivo ima več datotek! Več...

16. 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: 211; Prenosov: 102 Celotno besedilo (563,26 KB) Gradivo ima več datotek! Več...

17. Compactifications of deformed conifolds, branes and the geometry of qubitsMirjam Cvetič, G. W. Gibbons, Christopher N. Pope, 2016, izvirni znanstveni članek Opis: We present three families of exact, cohomogeneityone Einstein metrics in (2n + 2) dimensions, which are generalizations of the Stenzel construction of Ricciflat metrics to those with a positive cosmological constant. The first family of solutions are FubiniStudy metrics on the complex projective spaces CPn+1, written in a Stenzel form, whose principal orbits are the Stiefel manifolds V2(Rn+2) = SO(n+2)/SO(n) divided by Z(2). The second family are also EinsteinKahler metrics, now on the Grassmannian manifolds G(2)(Rn+3) = SO(n+3)/((SO(n+1)xSO(2)), whose principal orbits are the Stiefel manifolds V2(Rn+2) (with no Z(2) factoring in this case). The third family are Einstein metrics on the product manifolds Sn+1 x Sn+1, and are Kahler only for n = 1. Some of these metrics are believed to play a role in studies of consistent string theory compactifications and in the context of the AdS/CFT correspondence. We also elaborate on the geometric approach to quantum mechanics based on the Kahler geometry of FubiniStudy metrics on CPn+1, and we apply the formalism to study the quantum entanglement of qubits. Ključne besede: conformal field models, string theory, models of quantum gravity, differential geometry, algebraic geometry Objavljeno: 27.06.2017; Ogledov: 209; Prenosov: 106 Celotno besedilo (586,14 KB) Gradivo ima več datotek! Več...

18. Chiral fourdimensional Ftheory compactifications with SU(5) and multiple U(1)factorsMirjam Cvetič, Antonella Grassi, Denis Klevers, Hernan Piragua, 2014, izvirni znanstveni članek Opis: We develop geometric techniques to determine the spectrum and the chiral indices of matter multiplets for fourdimensional Ftheory compactifications on elliptic CalabiYau fourfolds with rank two MordellWeil group. The general elliptic fiber is the CalabiYau onefold in dP(2). We classify its resolved elliptic fibrations over a general base B. The study of singularities of these fibrations leads to explicit matter representations, that we determine both for U(1) xU(1) and SU(5) x U(1) x U(1) constructions. We determine for the first time certain matter curves and surfaces using techniques involving prime ideals. The vertical cohomology ring of these fourfolds is calculated for both cases and general formulas for the Euler numbers are derived. Explicit calculations are presented for a specific base B = P3. We determine the general G(4)flux that belongs to HV((2,2)) of the resolved CalabiYau fourfolds. As a byproduct, we derive for the first time all conditions on G(4)flux in general Ftheory compactifications with a nonholomorphic zero section. These conditions have to be formulated after a circle reduction in terms of ChernSimons terms on the 3D Coulomb branch and invoke Mtheory/Ftheory duality. New ChernSimons terms are generated by KaluzaKlein states of the circle compactification. We explicitly perform the relevant field theory computations, that yield nonvanishing results precisely for fourfolds with a nonholomorphic zero section. Taking into account the new ChernSimons terms, all 4D matter chiralities are determined via 3D Mtheory/Ftheory duality. We independently check these chiralities using the subset of matter surfaces we determined. The presented techniques are general and do not rely on toric data. Ključne besede: flux compactifications, Ftheory Objavljeno: 27.06.2017; Ogledov: 152; Prenosov: 107 Celotno besedilo (1,75 MB) Gradivo ima več datotek! Več...

19. 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: 241; Prenosov: 97 Celotno besedilo (598,59 KB) Gradivo ima več datotek! Več...

20. 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: 223; Prenosov: 90 Celotno besedilo (834,82 KB) Gradivo ima več datotek! Več...
