arXiv subjects

Zygmunt Lalak

Publications and source records attributed to Zygmunt Lalak.

At least 91 records · Page 5Linked to original sources

arXiv2001

Non-BPS Branes of Supersymmetric Brane Worlds

We consider five-dimensional brane worlds with N=2 gauged supergravity in the bulk coupled supersymmetrically to two boundary branes at the fixed points of a Z_2 symmetry. We analyse two mechanisms that break supersymmetry either by choosing flipped fermionic boundary conditions on the boundary branes or by modifying the gravitino variation to include both Z_2-odd and Z_2-even operators. In all cases we find the corresponding background. Including an even part in the gravitino variation leads to tilted branes. Choosing the flipped boundary conditions leads to AdS_4 branes and stabilized radion in the detuned case, when the expectation value of the even variation is nonzero. Another solution has the interpretation of moving AdS_4 branes separated by a horizon. The solution with moving branes separated by a horizon can be extended to the tuned case. In the presence of a horizon, temperature mediation communicates supersymmetry breakdown to the branes.

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arXiv2001

Low Energy Supersymmetry in Warped Brane Worlds

We discuss physical implications of the four-dimensional effective supergravity, that describes low-energy physics of the Randall--Sundrum model with moduli fields in the bulk and charged chiral matter living on the branes. Cosmological constant can be cancelled through the introduction of a brane Polonyi field and a brane superpotential for the 4d dilaton. We deduce a generalization of the effective 4d action to the case of a general, not necessarily exponential, warp factor. We note, that breakdown of supersymmetry in generic warped models may lead to the stabilization of the interbrane distance.

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arXiv2001

Supersymmetry and Vacuum Energy in Five-Dimensional Brane Worlds

We present the explicit form of the four-dimensional effective supergravity action which describes low-energy physics of the Randall--Sundrum model with moduli fields in the bulk and charged chiral matter living on the branes. The low-energy action is derived from the compactification of a locally supersymmetric model in five dimension. We describe the mechanism of supersymmetry breaking mediation which relies on the non-trivial configuration of the $Z_2$-odd bulk fields. Broken supersymmetry leads to stabilization of the interbrane distance.

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arXiv2001

Four-Dimensional Supergravities from Five-Dimensional Brane Worlds

We give the explicit form of the four dimensional effective supergravity action, which describes low energy physics of the Randall-Sundrum model with moduli fields in the bulk and charged chiral matter living on the branes. The relation between 5d and 4d physics is explicit: the low energy action is derived from the compactification of a locally supersymmetric model in five dimension. The presence of odd $Z_2$ parity scalars in the bulk gives rise to effective potential for the radion in four dimensions. We describe the mechanism of supersymmetry breaking mediation, which relies on non-trivial configuration of these $Z_2$-odd bulk fields. Broken supersymmetry leads to stabilization of the interbrane distance.

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arXiv2000

Five-Dimensional Gauged Supergravities with Universal Hypermultiplet and Warped Brane Worlds

We present five dimensional gauged supergravity with universal hypermultiplet on M_4 \times S^1 / Z_2 coupled supersymmetrically to three-branes located at the fixed points. The construction is extended to the smooth picture with auxiliary singlet and four-form fields. The model admits the Randall-Sundrum solution as a BPS vacuum with vanishing energy. We give the form of all KK-tower modes for fields present in the model.

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arXiv2000

The Cosmological Constant Problem from a Brane-World Perspective

We point out several subtleties arising in brane-world scenarios of cosmological constant cancellation. We show that solutions with curvature singularities are inconsistent, unless the contribution to the effective four-dimentional cosmological constant of the physics that resolves the singularities is fine-tuned. This holds for both flat and curved branes. Irrespective of this problem, we then study an isolated class of flat solutions in models where a bulk scalar field with a vanishing potential couples to a 3-brane. We give an example where the introduction of a bulk scalar potential results in a nonzero cosmological constant. Finally we comment on the stability of classical solutions of the brane system with respect to quantum corrections.

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arXiv2000

Supersymmetrizing Branes with Bulk in Five-Dimensional Supergravity

We supersymmetrize a class of moduli dependent potentials living on branes with the help of additional bulk terms in 5d N=2 supergravity. The space of Poincare invariant vacuum solutions includes the Randall-Sundrum solution and the $M$-theoretical solution. After adding gauge sectors to the branes we discuss breakdown of low energy supersymmetry in this setup and hierarchy of physical scales. In the limit of large warp factors we find decoupling between effects stemming from different branes in the compactified theory.

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arXiv2000

A Comment on Self-Tuning and Vanishing Cosmological Constant in the Brane World

In this note we elaborate on various five dimensional contributions to the effective 4D cosmological constant in brane systems. In solutions with vanishing 5D cosmological constant we describe a non-local mechanism of cancellation of vacuum energy between the brane and the singularities. We comment on a hidden fine tuning which is implied by this observation.

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arXiv1999

Target-Space Duality in Heterotic and Type I Effective Lagrangians

We study the implications of target-space duality symmetries for low-energy effective actions of various four-dimensional string theories. In the heterotic case such symmetries can be incorporated in simple orbifold examples. At present a similar statement cannot be made about the simplest type IIB orientifolds due to an obstruction at the level of gravitational anomalies. This fact confirms previous doubts concerning a conjectured heterotic-type IIB orientifold duality and shows that target-space symmetries can be a powerful tool in studying relations between various string theories at the level of the effective low-energy action. Contraints on effective Lagrangians from these symmetries are discussed in detail. In particular, we consider ways of extending T-duality to include additional corrections to the Kaehler potential in heterotic string models with N=2 subsectors.

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arXiv1999

Scales of Gaugino Condensation and Supersymmetry Breaking in Nonstandard M-Theory Embeddings

We investigate the formation of dynamical gaugino condensates and supersymmetry breaking in the compactifications of Horava-Witten theory with perturbative nonstandard embeddings. Specific models are considered where the underlying massless charged states of the condensing sector are determined by the spectra of $Z_2 \times Z_2 $ and $Z_4 $ orbifolds with nonstandard embeddings. We find among them viable examples where gaugino condensation is triggered on the wall with the weakest gauge coupling at $M_{GUT} $. In all these cases the magnitude of the condensate formed is below the energy scales at which extra dimensions are resolved, and so justifies the analysis of condensation in an effective 4-dimensional framework. We make some comments concerning the size of the largest extra dimension in the models considered. We discuss racetrack scenarios in the framework of perturbative nonstandard embeddings.

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arXiv1999

Supergravity and Supersymmetry Breaking in Four and Five Dimensions

We discuss supersymmetry breaking in the field-theoretical limit of the strongly-coupled heterotic string compactified on a Calabi-Yau manifold, from the different perspectives of four and five dimensions. The former applies to light degrees of freedom below the threshold for five-dimensional Kaluza-Klein excitations, whereas the five-dimensional perspective is also valid up to the Calabi-Yau scale. We show how, in the latter case, two gauge sectors separated in the fifth dimension are combined to form a consistent four-dimensional supergravity. In the lowest order of the $κ^{2/3}$ expansion, we show how a four-dimensional supergravity with gauge kinetic function $f_{1,2}=S$ is reproduced, and we show how higher-order terms give rise to four-dimensional operators that differ in the two gauge sectors. In the four-dimensional approach, supersymmetry is seen to be broken when condensates form on one or both walls, and the goldstino may have a non-zero dilatino component. As in the five-dimensional approach, the Lagrangian is not a perfect square, and we have not identified a vacuum with broken supersymmetry and zero vacuum energy. We derive soft supersymmetry-breaking terms for non-standard perturbative embeddings, that are relevant in more general situations such as type I/type IIB orientifold models.

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arXiv1999

String Dualities in the Presence of Anomalous U(1) Symmetries

Anomalous U(1) gauge symmetries in type II orientifold theories show some unexpected properties. In contrast to the heterotic case, the masses of the gauge bosons are in general of order of the string scale even in the absence of large Fayet-Iliopoulos terms. Despite this fact, the notion of heterotic-type II orientifold duality remains a useful concept, although this symmetry does not seem to hold in all cases considered. We analyse the status of this duality symmetry, clarify the properties of anomalous U(1) gauge symmetry in the orientifold picture and comment on the consequences for phenomenological applications of such anomalous gauge symmetries.

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arXiv1998

Five-Dimensional Gauged Supergravity and Supersymmetry Breaking in $M$~Theory

We extend the formulation of gauged supergravity in five dimensions, as obtained by compactification of $M$~theory on a deformed Calabi-Yau manifold, to include non-universal matter hypermultiplets. Even in the presence of this gauging, only the graviton supermultiplets and matter hypermultiplets can couple to supersymmetry breaking sources on the walls, though these mix with vector supermultiplets in the bulk. Whatever the source of supersymmetry breaking on the hidden wall, that on the observable wall is in general a combination of dilaton- and moduli-dominated scenarios.

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arXiv1998

Five-Dimensional Aspects of M-Theory Dynamics and Supersymmetry Breaking

We discuss the reduction of the eleven-dimensional M-theory effective Lagrangian, considering first compactification from eleven to five dimensions on a Calabi-Yau manifold, followed by reduction to four dimensions on an S_1/Z_2 line segment at a larger distance scale. The Calabi-Yau geometry leads to a structure of the five-dimensional Lagrangian that has more freedom than the eleven-dimensional theory. In five dimensions one obtains a non-linear sigma-model coupled to gravity, which implies non-trivial dynamics for the scalar moduli fields in the bulk of the Z_2 orbifold. We discuss solutions to the five-dimensional equations of motion in the presence of sources localized on the boundaries of the Z_2 orbifold that may trigger supersymmetry breaking, e.g., gaugino condensates. The transmission of supersymmetry breaking from the hidden wall to the visible wall is demonstrated in specific models. The role of the messenger of supersymmetry breaking may be played by the gravity supermultiplet and/or by scalar hypermultiplets. The latter include the universal hypermultiplet associated with the Calabi-Yau volume, and also the hypermultiplets associated with deformations of its complex structure, which mix in general.

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arXiv1998

Beyond the Standard Embedding in M-Theory on S^1/Z_2

In this paper we discuss compactifications of M-theory to four dimensions on X \times S^1/Z_2, in which nonstandard embeddings in the E_8 \times E_8 vacuum gauge bundle are considered. At the level of the effective field theory description of Horava and Witten, this provides a natural extension of well known results at weak coupling, to strongly coupled E_8 \times E_8 heterotic strings. As an application of our results, we discuss models which exhibit an anomalous U(1)_A symmetry in four dimensions, and show how this emerges from the reduction of the d = 11 toplogical term C \wedge G \wedge G, and how it is consistent with d = 4 anomaly cancellation in M-theory. As a further application of nonstandard embeddings, we show how it is possible to obtain an inverse hierarchy of gauge couplings, where the observable sector is more strongly coupled than the hidden one. The basic construction and phenomenological viability of these scenarios is demonstrated.

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arXiv1997

Gaugino Condensation, Moduli Potentials and Supersymmetry Breaking in M-Theory Models

We derive the explicit form, and discuss some properties of the moduli dependent effective potential arising from M-theory compactified on $M_4 \times X\times S^1 / Z_2 $, when one of the boundaries supports a strongly interacting gauge sector and induces gaugino condensation. We discuss the relation between the explicit gaugino condensate and effective superpotential formulations and find interesting differences with respect to the situation known from the weakly coupled heterotic string case. The moduli dependence of the effective potential turns out to be more complicated than expected, and perhaps offers new clues to the stabilization problem.

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arXiv1997

Soliton Solutions of M-theory on an Orbifold

We explicitly construct soliton solutions in the low energy description of M-theory on S^1/Z_2. It is shown that the 11-dimensional membrane is a BPS solution of this theory if stretched between the Z_2 hyperplanes. A similar statement holds for the 11-dimensional 5--brane oriented parallel to the hyperplanes. The parallel membrane and the orthogonal 5-brane, though solutions, break all supersymmetries. Furthermore, we construct the analog of the gauge 5-brane with gauge instantons on the hyperplanes. This solution varies nontrivially along the orbifold direction due to the gauge anomalies located on the orbifold hyperplanes. Its zero mode part is identical to the weakly coupled 10-dimensional gauge 5-brane.

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arXiv1997

Towards a Solution of the Cosmological Domain Walls Problem

We show that all kinds of biasing of cosmological phase transitions produce qualitatively new type of domain wall networks. The biased networks consist of compact, finite size, bag-like wall structures and exhibit a generic instability. The surface of biased networks disappears exponentially fast after a limited period of scaling. We argue that fluctuations of the background make the network unstable even in the case of the ``symmetric on the average'' initial distribution. We observe that the variation in parameters of the potential, like its hight, can influence the lifetime of the wall network, contrary to the standard beliefs.

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