We define a wave-function for string theory cosmological backgrounds. We give a prescription for computing its norm following an earlier analysis within general relativity. Under Euclidean continuation, the cosmologies we discuss in this paper are described in terms of compact parafermionic worldsheet systems. To define the wave-function we provide a T-fold description of the parafermionic conformal field theory, and of the corresponding string cosmology. In specific examples, we compute the norm of the wave-function and comment on its behavior as a function of moduli.
Using the recent observations of the relation between Hartle-Hawking wave function and topological string partition function, we propose a wave function for scalar metric fluctuations on S^3 embedded in a Calabi-Yau. This problem maps to a study of non-critical bosonic string propagating on a circle at the self-dual radius. This can be viewed as a stringy toy model for a quantum cosmology.
Exact string solutions are presented, where moduli fields are varying with time. They provide examples where a dynamical change of the topology of space is occurring. Some other solutions give cosmological examples where some dimensions are compactified dynamically or simulate pre-big bang type scenarios. Some lessons are drawn concerning the region of validity of effective theories and how they can be glued together, using stringy information in the region where the geometry and topology are not well defined from the low energy point of view. Other time dependent solutions are presented where…
A cosmological model for the early time Universe is proposed. In this model, the Universe is a wandering brane moving in a warped throat of a Calabi-Yau space. A non-zero angular momentum induces a turning point in the brane trajectory, and leads to a bouncing cosmology as experienced by an observer living on the brane. The Universe undergoes a decelerated contraction followed by an accelerating expansion and no big-bang singularity. Although the number of e-folds of accelerated motion is low (less than 2), standard cosmological problems are not present in our model thanks to the absence of an…
We further study the nonperturbative formulation of two-dimensional black holes. We find a nonlinear differential equation satisfied by the tachyon in the black hole background. We show that singularities in the tachyon field configurations are always associated with divergent semiclassical expansions and are absent in the exact theory. We also discuss how the Euclidian black hole emerges from an analytically continued fermion theory that corresponds to the right side up harmonic oscillator potential.
In the type IIB maximally supersymmetric pp-wave background, stringy excited modes are described by BMN (Berenstein-Madalcena-Nastase) operators in the dual $\mathcal{N}=4$ super-Yang-Mills theory. In this paper, we continue the studies of higher genus free BMN correlators with more stringy modes, mostly focusing on the case of genus one and four stringy modes in different transverse directions. Surprisingly, we find that the non negativity of torus two-point functions, which is a consequence of a previously proposed probability interpretation and has been verified in the cases with two and th…
We study a d-dimensional FRW universe, containing a perfect fluid with p = w ρand \frac{1} {d - 1} \le w \le 1, and find a correspondence principle similar to that of Horowitz and Polchinski in the black hole case. This principle follows quite generally from thermodynamics and the conservation of energy momentum tensor, and can be stated along similar lines as in the black hole case: ``When the temperature T of the universe becomes of order string scale the universe state becomes a highly excited string state. At the transition, the entropies and energies of the universe and strings differ by …
We obtain axionic charged primordial black holes on a vacuum created gravitational pair of $(3{\bar 3})$-brane by the Kalb-Ramond field on a $D_4$-brane in presence of a background open string metric. The new geometries on an emergent pair of $(3{\bar 3})$-brane universe is shown to be influenced by the non-perturbative quantum effects underlying a geometric torsion in a second order formalism. The presence of small extra dimensions transverse to the pair in the formalism ensures dynamical scalar fields hidden to a $3$-brane or an anti 3-brane universe. We investigate the non-perturbative quan…
In this paper we point out that the spacetime uncertainty relation proposed for string theory has strong cosmological implications that can solve the flatness problem and the horizon problem without the need of inflation. We make minimal assumptions about the very early universe.
It is generally considered as self evident that the lifetime of our vacuum in the landscape of string theory cannot be much shorter than the current age of the universe. Here I show why this lower limit is invalid. A certain type of ``parallel universes'' is a necessary consequence of the string-landscape dynamics and might well allow us to ``survive'' vacuum decay. As a consequence our stringy vacuum's lifetime is empirically unconstrained and could be very short. Based on this counter-intuitive insight I propose a novel type of laboratory experiment that searches for an apparent violation of…
In this paper we construct a stringy embedding of the dark bubble model of an expanding 4D cosmology with the help of branes rotating in extra dimensions. The universe rides a bubble which has nucleated in an unstable higher dimensional background. Our construction is therefore a string theoretical realization of Vilenkin's quantum cosmology. While the cosmological constant vanishes at lowest order, loop corrections predicted by the Weak Gravity Conjecture can induce a phenomenologically viable value. The model predicts the existence of large extra dimensions compatible with observational cons…
We construct boundary states for supertubes in the flat spacetime. The T-dual objects of supertubes are moving spiral D1-branes (D-helices). Since we can obtain these D-helices from the usual D1-branes via null deformation, we can construct the boundary states for these moving D-helices in the covariant formalism. Using these boundary states, we calculate the vacuum amplitude between two supertubes in the closed string channel and read the open string spectrum via the open closed duality. We find there are critical values of the energy for on-shell open strings on the supertubes due to the non…
In previous works we have derived a Running Vacuum Model (RVM) for a string Universe, which provides an effective description of the evolution of 4-dimensional string-inspired cosmologies from inflation till the present epoch. In the context of this "stringy RVM" version, it is assumed that the early Universe is characterised by purely gravitational degrees of freedom, from the massless gravitational string multiplet, including the antisymmetric tensor field. The latter plays an important role, since its dual gives rise to a `stiff' gravitational-axion "matter", which in turn couples to the gr…
We consider a universe with a non-classical stringy topology that has fixed points. We concentrate on the simplest example, an orbifold point, and study its observable imprints on the cosmic microwave background (CMB). We show that an orbifold preserves the Gaussian nature of the temperature fluctuations, yet modifies the angular correlation function. A direct signature of an orbifold is a single circle in the CMB that is invariant under rotation by 180 degrees. Searching the 7-year ILC map of WMAP, we find one candidate circle with high statistical significance. However, a closer look reveals…
A class of solutions of the low energy string theory in four dimensions is studied. This class admits a geodesic, shear-free null congruence which is non-twisting but in general diverging and the corresponding solutions in Einstein's theory form the Robinson-Trautman family together with a subset of the Kundt's class. The Robinson-Trautman conditions are found to be frame invariant in string theory. The Lorentz Chern-Simons three form of the stringy Robinson-Trautman solutions is shown to be always closed. The stringy generalizations of the vacuum Robinson-Trautman equation are obtained and th…
We argue that, for generic string compactifications, dark energy is likely to signal the beginning of the end of our universe, perhaps even through decompactification, with possible implications for the cosmological coincidence problem. Thanks to the scarcity (absence?) of stable de Sitter vacua, dark energy in string theory is assumed to take the form of a quintessence field in slow roll. As it rolls, a tower of heavy states will generically descend, triggering an apocalyptic phase transition in the low energy cosmological dynamics after at most a few hundred Hubble times. As a result, dark e…
We present plane-wave-type solutions of the lowest order superstring effective action which have unbroken space-time supersymmetries. They describe dilaton, axion and gauge fields in a stringy generalization of the Brinkmann metric. Some conspiracy between the metric and the axion field is required. We show that there exists a special class of these solutions, for which $α^\prime$ stringy corrections to the effective on-shell action, to the equations of motion (and therefore to the solutions themselves), and to the supersymmetry transformations vanish. We call these solutions supersymmetric st…
Starting from microscopic models of space-time foam, based on brane universes propagating in bulk space-times populated by D0-brane defects ("D-particles"), we arrive at effective actions used by a low-energy observer on the brane world to describe his/her observations of the Universe. These actions include, apart from the metric tensor field, also scalar (dilaton) and vector fields, the latter describing the interactions of low-energy matter on the brane world with the recoiling point-like space-time defect (D-particle). The vector field is proportional to the recoil velocity of the D-particl…
We argue that string theory has all the ingredients to provide us with candidates for the cold dark matter and explain the current acceleration of our Universe. In any generic string compactification the dilaton plays an important role as it couples to the Standard Model and other heavy non-relativistic degrees of freedom such as the string winding modes and wrapped branes, we collectively call them stringy cold dark matter. These couplings are non-universal which results in an interesting dynamics for a rolling dilaton. Initially, its potential can track radiation and matter while beginning t…
The Kerr spinning particle has a remarkable analytical twistorial structure. Analyzing electromagnetic excitations of the Kerr circular string which are aligned to this structure, we obtain a simple stringy skeleton of the spinning particle which is formed by a topological coupling of the Kerr circular singular string and by an axial singular stringy system. We show that the chiral traveling waves, related to an orientifold world-sheet of the axial stringy system, are described by the massive Dirac equation, so we argue that the axial string may play the part of a stringy carrier of wave funct…
The cubic interaction vertex and the dynamical supercharges are constructed for open strings ending on D7-branes, in light-cone superstring field theory in PP-wave background. In this context, we write down the symmetry generators in terms of the relevant group structure: SU(2) x SU(2) x SO(2) x SO(2), originating from the eight transverse directions in the PP-wave background and use the expressions to explicitly construct the vertex at the level of stringy zero modes. The results are further generalized to include all the stringy excitations as well.
We consider the problem of constructing a non-singular inflationary universe in stringy gravity via branch changing, from a previously superexponentially expanding phase to an FRW-like phase. Our approach is based on the phase space analysis of the dynamics, and we obtain a no-go theorem which rules out the efficient scenario of branch changing catalyzed by dilaton potential and stringy fluid sources. We furthermore consider the effects of string-loop corrections to the gravitational action in the form recently suggested by Damour and Polyakov. These corrections also fail to produce the desire…
We study cosmological solutions to the low-energy effective action of heterotic string theory including possible leading order $α'$ corrections and a potential for the dilaton. We consider the possibility that including such stringy corrections can resolve the initial cosmological singularity. Since the exact form of these corrections is not known the higher-derivative terms are constructed so that they vanish when the metric is de Sitter spacetime. The constructed terms are compatible with known restrictions from scattering amplitude and string worldsheet beta-function calculations. Analytic …
In low-energy effective string theory, $α'$ corrections involve the coupling of the dilaton field to Gauss-Bonnet term. We assume that the dilaton potential is fine tuned so that the dilaton field may oscillate rapidly for a while around the minimum of its potential but the inflation background is not affected. By numerical method, we find that if the dilaton starts to oscillate at the time of about $\sim 60$ e-folds before the end of inflation, $α^\prime$ correction may bring unusual oscillations to the inflationary gravitational wave spectrum, which might be measurably imprinted in the CMB B…
Cryptons, metastable bound states of matter in the string hidden sector, with dynamically determined masses M_X on the order of 10^{12} GeV and lifetimes tau_X greater than or on the order of 10^{18} yr, may be generated, through inflation, with an abundance close to that required for a near-critical universe. Their decay debris may be responsible for the most energetic particles striking Earth's atmosphere. Recent developments of this astonishing hypothesis are reviewed, indicating that NESTOR or the PIERRE AUGER project may be able to confirm or refute the existence of cryptons.
In a previous publication by some of the authors (N.E.M., M.S. and M.F.Y.), we have argued that the "D-material universe", that is a model of a brane world propagating in a higher-dimensional bulk populated by collections of D-particle stringy defects, provides a model for the growth of large-scale structure in the universe via the vector field in its spectrum. The latter corresponds to D-particle recoil velocity excitations as a result of the interactions of the defects with stringy matter and radiation on the brane world. In this article, we first elaborate further on the results of the prev…
Misner space, also known as the Lorentzian orbifold $R^{1,1}/boost$, is the simplest tree-level solution of string theory with a cosmological singularity. We compute tree-level scattering amplitudes involving twisted states, using operator and current algebra techniques. We find that, due to zero-point quantum fluctuations of the excited modes, twisted strings with a large winding number $w$ are fuzzy on a scale $\sqrt{\log w}$, which can be much larger than the string scale. Wave functions are smeared by an operator $\exp(Δ(ν) \partial_+ \partial_-)$ reminiscent of the Moyal-product of non-co…
In the Cosmological Slingshot Scenario, our Universe is a D3-brane that extends in the 4d noncompact directions of a warped Calabi-Yau compactification of IIB Supergravity. Early time cosmology corresponds to a period in which the brane moves inside a warped throat where a non-vanishing angular momentum ensures that the trajectory of the brane has a turning point. The corresponding induced metric on the D3-brane experiences a cosmological evolution with a bounce. In this framework, the homogeneity, flatness, and isotropy problems of standard cosmology might be avoided. The power spectrum of pr…
We propose a variation of spacetime noncommutative field theory to realize the stringy spacetime uncertainty relation without breaking any of the global symmetries of the homogeneous isotropic universe. We study the spectrum of metric perturbations in this model for a wide class of accelerating background cosmologies. Spacetime noncommutativity leads to a coupling between the fluctuation modes and the background cosmology which is nonlocal in time. For each mode, there is a critical time at which the spacetime uncertainty relation is saturated. This is the time when the mode is generated. Thes…
We investigate stringy excitations in Randall-Sundrum effective theories for electroweak symmetry breaking arising from embedding in string theory. RS is dual to a confining gauge theory, which we expect to have "QCD strings," or color flux tubes. Stringy constructions of RS-like theories allow us to investigate the mass of these string states, which typically grows with a small fractional power of the number of colors N of the dual gauge theory. There are two known strong constraints on N for RS-like theories. The first arises from demanding that the Standard Model gauge couplings do not have…
We show that the frame of the Kerr spinning particle consists of two topologically coupled strings. One of them is the Kerr singular ring representing a string with an orientifold world-sheet. It has electromagnetic excitations (traveling waves), which corresponds to the old model of the Kerr's microgeon. The excitations induce the appearance of the extra axial string which is topologically coupled to the Kerr circular string and is a carrier of pp-waves and fermionic zero modes. This string can be described by the Witten field model for superconducting strings.
A classical spinning particle based on the Kerr-Newman black hole (BH) solution is considered. For parameters of spinning particles $|a|>>m$, the BH horizons disappear and BH image is drastically changed. We show that it turns into a skeleton formed by two coupled stringy systems. One of them is the Kerr singular ring which can be considered as a circular D-string with an orientifold world-sheet. Analyzing the aligned to the Kerr congruence electromagnetic excitations of this string, we obtain the second stringy system which consists of two axial half-infinite chiral D-strings. These axial str…
I discuss a model inspired from the string/brane framework, in which our Universe is represented as a three brane, propagating in a bulk space time punctured by D0-brane (D-particle) defects. As the D3-brane world moves in the bulk, the D-particles cross it, and from an effective observer on D3 the situation looks like a ``space-time foam'' with the defects ``flashing'' on and off (``D-particle foam''). The open strings, with their ends attached on the brane, which represent matter in this scenario, can interact with the D-particles on the D3-brane universe in a topologically non-trivial manne…
The theory of cosmological fluctuations assumes that the pre-inflationary state of the universe was the quantum vacuum of a scalar field(s) coupled to gravity. The observed cosmic microwave background fluctuations are then interpreted as quantum fluctuations. Here we consider alternate interpretations of the classic calculations of scalar and tensor power spectra by replacing the Bunch-Davies quantum vacuum with a classical statistical distribution, which may have been the consequence of a pre-inflationary process of decoherence as in the quantum cosmology literature. Mathematically they are e…
In this paper we revisit the formulation of scalar field theories on de Sitter backgrounds subject to the generalized uncertainty principle (GUP). The GUP arises in several contexts in string theory, but is most readily thought of as resulting from using strings as effective probes of geometry, which suggests an uncertainty relation incorporating the string scale $l_s$. After reviewing the string theoretic case for the GUP, which implies a minimum length scale $l_s$, we follow in the footsteps of Kempf and concern ourselves with how one might write down field theories which respect the GUP. We…
We start by pointing out that certain Riemann surfaces appear rather naturally in the context of wave equations in the black hole background. For a given black hole there are two closely related surfaces. One is the Riemann surface of complexified ``tortoise'' coordinate. The other Riemann surface appears when the radial wave equation is interpreted as the Fuchsian differential equation. We study these surfaces in detail for the BTZ and Schwarzschild black holes in four and higher dimensions. Topologically, in all cases both surfaces are a sphere with a set of marked points; for BTZ and 4D Sch…
Brane inflation is a specific realization of the inflationary universe scenario in the early universe within the brane world framework in string theory. The naturalness and robustness of this realistic scenario is explained. Its predictions on the cosmological observables in the cosmic microwave background radiation, especially possible distinct stringy features, such as large non-Gaussianity or large tensor mode that deviates from that predicted in the slow roll scenario, are discussed. Stringy KK modes as hidden dark matter is also a possibility. Another generic consequence of brane inflatio…
The structure of classical spinning particle based on the Kerr-Newman black hole (BH) solution is investigated. For large angular momentum, $|a|>>m$, the BH horizons disappear exposing a naked ringlike source which is a circular relativistic string. It was shown recently that electromagnetic excitations of this string lead to the appearance of an extra axial stringy system which consists of two half-infinite strings of opposite chirality. In this paper we consider the relation of this stringy system to the Dirac equation. We also show that the axial strings are the Witten superconducting strin…
Space-filling S-branes can mediate a transition between a contracting and an expanding universe in the Einstein frame. Following up on previous work that uncovered such bouncing solutions in the context of weakly coupled thermal configurations of a certain class of type II superstrings, we set up here the formalism in which we can study the evolution of metric fluctuations across such an S-brane. Our work shows that the specific nature of the S-brane, which is sourced by non-trivial massless thermal string states and appears when the universe reaches a maximal critical temperature, allows for …
We propose an alternative scenario to cosmic inflation for producing the initial seeds of cosmic structures. The cosmological fluctuations are generated by thermal fluctuation of the energy density of the ideal string gas in three compact spatial dimensions. Statistical mechanics of the strings reveals that scalar power spectrum of the cosmological fluctuations on cosmic scales is scale-invariant for closed strings and inclines towards red for open strings in three compact spatial dimensions. This generation of thermal fluctuations happens during the Hagedorn era of string gas cosmology and wi…
In this thesis, we study the details of some fundamental cosmological problems of the gauge mediated supersymmetry breakdown and we probe the supersymmetry breaking sector by cosmological arguments. We manifest that problems like the metastable vacuum selection and the gravitino overproduction in the reheated early universe are naturally absent in the most general class of gauge mediation models without including additional ingredients or assumptions. We also find that the gravitino can generically account for the bulk dark matter of the universe. Cosmological implications of a stringy UV-comp…
The cosmological evolution of the string landscape is expected to consist of multiple stages of old inflation with large cosmological constant ending by tunnelling. Old inflation has a well known graceful exit problem as the observable universe becomes empty, devoid of any entropy. Simultaneously, in the quest for reheating the right degrees of freedom, it is important that the final stage of inflation reheat Standard Model sector. It is known that inflation can occur naturally along a flat direction of the Minimal Supersymmetric Standard Model (MSSM), solving the reheating problem, but the in…
We propose a new holographic C-function for the accelerating universe defined in the stringy frame motivated mainly by the fact that the number of degrees of freedom should be infinite for a physical system of infinite size. This is the generalization of Strominger's recent proposal of the holographic C-function to the asymptotically non-de Sitter universe. We find that the corresponding C-theorem holds true if the universe accelerates toward the weak coupling regime driven by the exponential dilaton potential. It also holds in other simple cases.
General ideas of gauge/gravity duality allow for the possibility of time dependent solutions that interpolate between a perturbative gauge theory phase and a weakly curved string/gravity phase. Such a scenario applied to cosmology would exhibit a non-geometric phase before the big bang. We investigate a toy model for such a cosmology, whose endpoint is the classical limit of the two-dimensional non-critical string. We discuss the basic dynamics of this model, in particular how it evolves toward the double scaling limit required for stringy dynamics. We further comment on the physics that will …
In previous works we have embedded the Running Vacuum Model (RVM) of Cosmology in the framework of string theory. Specifically, we considered a string-inspired Cosmology with primordial gravitational waves (GW) and gravitational anomalies, which were argued to lead, via appropriate condensation during the very-early-universe era, to dynamical inflation, of RVM type, without the need for extra inflaton fields. A crucial role for the associated slow-roll nature of the inflationary era was played by the fundamental axion field that exists in the gravitational multiplet of strings, viz. the Kalb-R…
Based on the observation that $AdS_5\times S^5/Z_k$ orbifolds have a maximal supersymmetric PP-wave limit, the description of strings in PP-waves in terms of ${\cal N}=2$ quiver gauge theories is presented. We consider two different, small and large $k$, cases and show that the operators in the gauge theory which correspond to stringy excitations are labelled by two integers, the excitation and winding or momentum numbers. For the large $k$ case, the relation between the space-time and worldsheet deconstructions is discussed. We also comment on the possible duality between these two cases.
From infinite to infinitesimal: Using the Universe as a dataset to probe Casimir corrections to the vacuum energy from fields inhabiting the dark dimension
String tension fundamentally determines the properties of strings; yet its value is often assigned arbitrarily, creating a fine-tuning problem. We describe a mechanism for dynamically generating string tension in a flat or almost flat spacetime, using the modified measures formalism, which in turn naturally generates a new type of stringy brane-world scenario. Such a scenario allows strings to achieve near infinite tension confining the strings to two very close expanding surfaces, but the infinite tensions also threatens to distort the near-flat embedding spacetime through large back reaction…
We study some gravitational instanton solutions that offer a natural realization of the spontaneous creation of inflationary universes in the brane world context in string theory. Decoherence due to couplings of higher (perturbative) modes of the metric as well as matter fields modifies the Hartle-Hawking wavefunction for de Sitter space. Generalizing this new wavefunction to be used in string theory, we propose a principle in string theory that hopefully will lead us to the particular vacuum we live in, thus avoiding the anthropic principle. As an illustration of this idea, we give a phenomen…
We construct a manifestly SO(4) x SO(4) invariant, supersymmetric extension of the closed string cubic interaction vertex and dynamical supercharges in light-cone string field theory on the plane wave space-time. We find that the effective vertex for states built out of bosonic creation oscillators coincides with the one previously constructed in the SO(8) formalism and conjecture that in general the two formulations are physically equivalent. Further evidence for this claim is obtained from the discrete Z_2-symmetry of the plane wave and by computing the mass-shift of the simplest stringy sta…
We discuss stringy ${α'}$ corrections to the gravitational wave signal generated in the merging of two black holes. We model the merging with two BPS compact massive objects in the heterotic string, described by standard vertex operators or coherent states. Despite the expected cubic suppression in ${α'}$ w.r.t. the General Relativity result, at tree level the string corrections seem to leave a footprint or a memory on the gravitational wave signals within the sensitivity region of aLIGO/VIRGO and future interferometers. Including loop effects that broaden and destabilise the string resonances…
We consider the nonrelativistic field theory with a quartic interaction on a noncommutative plane. We compute the four point scattering amplitude within perturbative analysis to all orders and identify the beta function and the running of the coupling constant. Since the theory admits an equivalent description via the N particle Schrodinger equation, we regain the scattering amplitude by finding an exact scattering wavefunction of the two body equation. The wave function for the bound state is also identified. These wave functions unusually have two center positions in the relative coordinates…
I discuss a specific model of space-time foam, inspired by the modern non-perturbative approach to string theory (D-branes). The model views our world as a three brane, intersecting with D-particles that represent stringy quantum gravity effects, which can be real or virtual. In this picture, matter is represented generically by (closed or open) strings on the D3 brane propagating in such a background. Scattering of the (matter) strings off the D-particles causes recoil of the latter, which in turn results in a distortion of the surrounding space-time fluid and the formation of (microscopic, i…
In this paper, based on the notion of plane wave string/gauge theory duality, we explore the pp wave limit associated with the bosonic sector of $ η$ deformed superstrings propagating in $ (AdS_5 \times S^{5})_η $. Our analysis reveals that in the presence of NS-NS and RR fluxes, the pp wave limit associated to full ABF background satisfies type IIB equations in its standard form. However, the beta functions as well as the string Hamiltonian start receiving non trivial curvature corrections as one starts probing beyond pp wave limit which thereby takes solutions away from the standard type IIB…
A characteristic spectrum of relic gravitational radiation is produced by a period of ``stringy inflation" in the early universe. This spectrum is unusual, because the energy-density rises rapidly with frequency. We show that correlation experiments with the two gravitational wave detectors being built for the Laser Interferometric Gravitational Observatory (LIGO) could detect this relic radiation, for certain ranges of the parameters that characterize the underlying string cosmology model.
We revisit the cubic interaction of IIB string theory in the maximally supersymmetric pp-wave background. In the supergravity limit, we show that detailed comparison with AdS supergravity determine the vertex completely. Extension of this supergravity vertex to the full string theory leads to a new cubic vertex that combines the previous proposals and contains additional terms. We give an alternative derivation of the holographic duality map in supergravity, first found by Dobashi and Yoneya (hep-th/0406225) and show that our new vertex is consistent with it. We compare some non-BPS amplitudes…
We find exact rotating and non-rotating neutral black hole solutions in the Godel universe of the five dimensional minimal supergravity theory. We also describe the embedding of this solution in M-theory. After dimensional reduction and T-duality, we obtain a supergravity solution corresponding to placing a black string in a pp-wave background.
