arXiv subjects

Lisa Randall

Publications and source records attributed to Lisa Randall.

At least 19 recordsLinked to original sources

arXiv2026

A Warped Extra Dimensional Candidate for the LZ 248 keV Event

The recent result by the LUX-ZEPLIN (LZ) experiment of a single nuclear-recoil event at $248\,\mathrm{keV}$ suggests an interpretation in terms of inelastic scattering between dark matter (DM) and the xenon target. The widely considered thermal Higgsino DM with $m_{\chi}\sim$~TeV and mass splitting $\delta \sim 350$~keV is essentially excluded as it would be captured efficiently by the Sun, with a resulting neutrino flux from its annihilation in excess of the IceCube limit, and expected recoils above the LZ nominal search window, where none were seen. However we argue that although these tensions apply to a Higgsino with constrained cross section, they need not apply to the broader set of inelastic candidates that alternative solutions to the hierarchy problem might suggest. We show that a new massive gauge boson, $Z'$ with a candidate DM sector and Majorana mass splitting of order $\sim 10^{-7}$ of the Dirac mass, evades current constraints. We propose an inelastic dark matter (iDM) candidate that can arise naturally in a Randall-Sundrum warped extra-dimensional model. The DM candidate involves a vector-like fermion confined to the TeV brane and a bulk field. The brane Lagrangian contains Dirac mass terms that are also naturally exponentially suppressed. The left-handed component of the bulk field has a Majorana mass with origin on the UV brane, while the interaction with Standard Model nucleons is mediated by a massive dark Kaluza-Klein (KK) gauge boson whose mass is also automatically in the right range. We propose a concrete model of thermal DM with $m_{\chi}\sim$~TeV in an RS geometry with warp factor $\pi kR\simeq 31.7$ and the $Z'$ a KK mode with natural TeV-ish scale mass in which the ratio of neutrino to quark coupling is also natural, giving a mass splitting of $\delta \sim 300$~keV, and show how it could explain the LZ signal while being consistent with existing constraints.

hep-ph↗

arXiv2026

Covariant Locally Localized Gravity and vDVZ Continuity

The Karch-Randall braneworld concerns the physics of an AdS$_{d}$ brane embedded in an ambient gravitational AdS$_{d+1}$ spacetime. The gravitational theory induced on the AdS$_{d}$ brane has a very light but massive graviton. It has been established that the zero graviton mass limit of the $d$-dimensional graviton propagator is smooth at tree-level. Furthermore, this smoothness was conjectured to persist to the quantum level. This conjecture suggests that the massive graviton on the AdS$_{d}$ brane is due to spontaneous symmetry breaking, which is consistent with its holographic dual description. In this letter, we show that the zero mass limit of the partition function is a theory of a massless graviton and a decoupled massive vector. The zero mass limit is not the basic Randall-Sundrum II model, but a theory with these additional decoupled vector degrees of freedom coupled only to gravity. The proof relies on deriving the fully covariant description of the $d$-dimensional gravity theory which enables us to compute the one-loop partition function. At the end, we comment on the implications of this result to the physics of entanglement islands.

hep-th↗

arXiv2026

Seeing Page Curves and Islands with Blinders On

This paper summarizes recent discussions of the Page curve and the information paradox, and responds to the reasoning and examples from arXiv:2506.04311. We review arguments demonstrating that in quantum gravity the algebra of observables at infinity is complete, both in AdS and in asymptotically flat space. This completeness implies that the bulk Hilbert space in quantum gravity does not factorize along the radial direction, undermining a key common assumption in Hawking's argument for information loss and in initial derivations of the Page curve. As a consequence, in a standard theory of gravity, information does not ``emerge'' from a black hole in the manner suggested by the Page curve; rather, it is already encoded in asymptotic observables. Relatedly, the full black hole interior, and not just an ``island'', can be reconstructed from exterior data. Page curves and islands can be obtained by removing the Hamiltonian from the exterior algebra. This may be implemented operationally by restricting access to part of the asymptotic region (a detector with a ``blind spot'') or, in the special case of null infinity in asymptotically flat spacetimes, by formally discarding the Hamiltonian from the set of observables despite its physical accessibility. Such Page curves describe only the redistribution of information between measured and unmeasured degrees of freedom, rather than fundamental information recovery. Finally, Page curves and islands also arise when a black hole is coupled to a nongravitational bath, a setup that yields a nonstandard theory of gravity. We show how, even in this setting, the unusual localization of information in gravity provides a concrete physical mechanism for information transfer from the gravitational system into the bath.

hep-th↗

arXiv2025

Wet Hair: Global Symmetries in Entanglement Islands

A central conjecture in quantum gravity is the non-existence of global symmetries. As a fully unitary theory, there is no information loss in a UV complete quantum gravity theory. We see both these concepts reflected in the AdS/CFT correspondence, which tells us that dynamical processes in AdS are fully captured by a manifestly unitary CFT with no information loss. Furthermore, global symmetries of the CFT are dual to gauge symmetries in the AdS, which implies no global symmetry in the AdS. In this work, we provide concrete evidence for the connection between the non-existence of global symmetries and the absence of information loss in quantum gravity. We study the $\textit{island setups}$ in which a gravitational AdS is coupled with a nongravitational bath on its boundary. In such theories, the information in the AdS can be lost to the bath. We provide concrete examples with global symmetries in the island setup, from both the bottom-up and the top-down perspectives. We argue that these global symmetries are consistent due to $\textit{entanglement islands}$, in which holography is realized in a novel fashion. The global symmetries we construct are all mixed with spontaneously broken gauge symmetries. We will show that this fact has two implications: $\textbf{1)}$ The black hole hair is detectable in the bath (``wet hair"); $\textbf{2)}$ a resolution of a puzzle proposed by Harlow and Shaghoulian.

hep-th↗

arXiv2025

Inflation with a Growing Fifth Dimension

Inflation generally assumes a field with nonzero potential that leads to inflationary expansion happening at arbitrarily early times. We demonstrate potentially observable consequences of inflation with a finite initial time in a model in five-dimensional warped anti-de Sitter space, with both a UV and an IR brane present during inflation. Considering an inflaton with an approximately flat potential localized on the UV brane, we derive the resulting brane motion in the bulk and the 4D effective action describing the dynamics. A concrete model allows us to evaluate possible consequences of a starting point of inflation. The background evolution is driven by the fast roll of the radion at early times and the slow roll of the inflaton at late times. We find that the action has the form of a two-field hyperbolic inflation model, the two fields being the radion and the inflaton, both of which have a time-dependent background solution. This setup is holographically dual to an inflaton coupled to a strongly coupled confining sector in which the ratio of the confinement scale to the 4D Planck scale evolves cosmologically. Focusing on the period when the equation of state becomes that of inflation, we find that the presence of the IR brane leads to deviations from the approximate de Sitter background in addition to those from the slow-roll parameters of the inflaton potential. We quantify the effect of the presence of the IR brane on the two point function of the adiabatic scalar perturbations and tensor perturbations. The dominant deviations occur at large scales: the adiabatic power spectrum has a blue tilt, while the tensor power spectrum shows oscillatory features. We present numerical fits to the shape of the adiabatic power spectrum, and discuss the implications for cosmic microwave background (CMB) analysis.

hep-th↗

arXiv2025

More Effective RS Field Theory

In this paper we derive the effective theory for a stabilized five-dimensional warped geometry, addressing several outstanding issues in this derivation. These include allowing for a non-zero 4d cosmological constant, accounting for constraints from both the UV and IR branes, and determining how the stabilized theory responds to an energy perturbation on each brane. We show how a consistent low-energy effective theory from a stable warped solution must respect a constraint that follows from the higher-dimensional Einstein equation. Satisfying the constraint requires that the 4d cosmological constant must be the same everywhere throughout the bulk, which means the stabilizing fields must adjust to allow for the same 4d curvature everywhere in the extra dimension. We show explicitly how this works in a 5d model, and how the correct 4d effective potential reproduces this behavior. We find that the cosmological constant generated from adding energy to one of the branes is unaffected by the details of the stabilization mechanism at leading order, despite the need for the stabilizing fields to adjust. In anticipation of a companion paper, we also briefly discuss how supersymmetry can be realized consistently in the 5d theory. In particular, we show how the stabilization mechanism remains consistent with sequestering, even as the supersymmetry-breaking energy is reflected in the stabilizing field throughout the bulk.

hep-ph↗

arXiv2025

Sequestered Conformal Anomaly Mediation (SCAM)

Supersymmetric models in singular extra dimensional spaces feature prominently in many interesting phenomenological models, including those derived from string theory. In this paper we explicitly derive the low energy theory of phenomenologically viable supersymmetric theories in five dimensions, and highlight several aspects of these models that are not obvious from working solely in the 4d effective theory. Important deviations arise for anomaly mediation, which is purported to be a predictive mechanism to mediate supersymmetry (SUSY) breaking that is naturally most relevant in extra dimensional theories. Despite this, most analyses of anomaly mediation have been performed in the 4d effective theory. We fill this gap in the literature by constructing stabilized supersymmetric theories in 5d and studying supersymmetry breaking and anomaly mediation. Studying Sequestered Conformal Anomaly-Mediated (SCAM) in full generality reveals important deviations from the 4d EFT expectations, particularly for the role of boundary superpotentials, the radion and the predicted universality of anomaly mediation. We discuss the requirements for viable extra dimensional models of SUSY-breaking, and demonstrate when and how the anomaly-mediated masses in 5d reduce to the na{\i}ve 4d supersymmetric result. In many cases supersymmetry is necessarily broken at the 5d level, leading to anomaly-mediated and other supersymmetry breaking masses that are not derivable in a simple supersymmetric 4d EFT, but need to be included as matching corrections. We comment on the potential implications of our methods for phenomenology and singular higher-dimensional constructions, such as the KKLT scenario.

hep-th↗

arXiv2025

Holography and Causality in the Karch-Randall Braneworld

It has been argued that the existence of a geodesic shortcut in the Karch-Randall (KR) braneworld rules out the possibility for a low-energy intermediate theory, even when gravity is turned off. We study this problem in an explicit example with two symmetrically placed KR branes. We find that there can be a consistent quantization of bulk matter fields with a holographic intermediate description. In our model, there is no causality violation. We use this example to study potential implications of the bulk geodesic shortcut. We find that there are possible enhancements of the correlation or entanglement between the two branes that is directly correlated with the extra-dimensional geometry. This could affect the low-energy regime when there are interactions between low and high energy modes. Our model makes it clear that any possible causality violation can only arise from the UV. Independently of the quantization, an intermediate description should be valid as an EFT.

hep-th↗

arXiv2024

Mass Beyond Measure: Eccentric Searches for Black Hole Populations

Stellar mass binary black holes of unknown formation mechanism have been observed, motivating new methods for distinguishing distinct black hole populations. This work explores how the orbital eccentricity of stellar mass binary black holes is a viable conduit for making such distinctions. Four different production mechanisms, and their corresponding eccentricity distributions, are studied in the context of an experimental landscape composed of mHz (LISA), dHz (DECIGO), and Hz (LIGO) range gravitational wave detectors. We expand on prior work considering these effects at fixed population eccentricity. We show that a strong signal corresponding to subsets of eccentric populations is effectively hidden from the mHz and dHz range gravitational wave detectors without the incorporation of high eccentricity waveform templates. Even with sufficiently large eccentricity templates, we find dHz range experiments with a LISA-like level of sensitivity are unlikely to aid in distinguishing different populations. We consider the degree to which a mHz range detector like LISA can differentiate among black hole populations independently and in concert with follow-up merger detection for binaries coalescing within a 10 year period. We find that mHz range detectors, with only $e < 0.01$ (nearly circular) sensitivity, can successfully discern eccentric sub-populations except when attempting to distinguish very low eccentricity distributions. In these cases where $e < 0.01$ sensitivity is insufficient, we find that the increase in event counts resulting from $e < 0.1$ sensitivity provides a statistically significant signal for discerning even these low eccentricity sub-populations. While improvements offered by $e<0.1$ sensitivity can be generally increased by $\mathcal{O}(1)$ factors with $e<0.4$ sensitivity, going beyond this in eccentricity sensitivity provides negligible enhancement.

gr-qc↗

arXiv2024

Phase Transition to RS: Cool, not Supercool

Motivated by the warped conifold compactification, we model the infrared (IR) dynamics of confining gauge theories in a Randall-Sundrum (RS)-like setup by modifying the stabilizing Goldberger-Wise (GW) potential so that it becomes large (in magnitude) in the IR and back-reacts on the geometry. We study the high-temperature phase by considering a black brane background in which we calculate the entropy and free energy of the strongly back-reacted solution. As with Buchel's result for the conifold (arXiv:2103.15188), we find a minimum temperature beyond which the black brane phase is thermodynamically unstable. In the context of a phase transition to the confining background, our results suggest that the amount of supercooling that the metastable black brane phase undergoes can be limited. It also suggests the first-order phase transition (and the associated gravitational waves from bubble collision) is not universal. Our results therefore have important phenomenological implications for early universe model building in these scenarios.

hep-ph↗

arXiv2023

Consequences of a Stabilizing Field's Self-Interactions for RS Cosmology

It has been argued that the Randall-Sundrum (RS) phase transition rate is suppressed when the holographic theory corresponds to a large $N$ Yang-Mills and when the stabilizing field has a small mass. Here we argue that self-interactions can alleviate the latter suppression. We consider a cubic term in the bulk potential for the Goldberger-Wise (GW) scalar that is responsible for stabilizing the RS geometry. Adding a cubic term suffices to separate the two roles of the GW stabilization: generating a large hierarchy and triggering confinement. We study the resulting radion potential and the dynamics of the early universe phase transition. For a negative coefficient of the cubic term, the effect of the cubic becomes important in the infra-red, and the resulting radion potential is deeper, thereby increasing the radion mass while maintaining a large hierarchy. Staying within the radion effective field theory, we calculate the rate of bubble nucleation from the hot phase to the confined RS phase, both in thin and thick wall limits. The cubic term enhances the rate and allows relaxing the condition on the maximum number of colors $N_\text{max}$ of the dual theory for which the phase transition can be completed. Importantly, this reduces the amount of supercooling that the false vacuum undergoes, increases the peak frequency of the gravitational waves (GW) produced from bubble collisions, and reduces the strength of the GW signal. The reduced GW signal is however still within the reach of proposed space-based GW detectors.

hep-ph↗

arXiv2023

Constraining braneworlds with entanglement entropy

We propose swampland criteria for braneworlds viewed as effective field theories of defects coupled to semiclassical gravity. We do this by exploiting their holographic interpretation. We focus on general features of entanglement entropies and their holographic calculations. Entropies have to be positive. Furthermore, causality imposes certain constraints on the surfaces that are used holographically to compute them, most notably a property known as causal wedge inclusion. As a test case, we explicitly constrain the Dvali--Gabadadze--Porrati term as a second-order-in-derivatives correction to the Randall--Sundrum action. We conclude by discussing the implications of these criteria for the question on whether entanglement islands in theories with massless gravitons are possible in Karch--Randall braneworlds.

hep-th↗

arXiv2023

Savior Curvatons and Large non-Gaussianity

Curvatons are light (compared to the Hubble scale during inflation) spectator fields during inflation that potentially contribute to adiabatic curvature perturbations post-inflation. They can alter CMB observables such as the spectral index $n_s$, the tensor-to-scalar ratio $r$, and the local non-Gaussianity $\;f_{\rm NL}^{\rm (loc)}$. We systematically explore the observable space of a curvaton with a quadratic potential. We find that when the underlying inflation model does not satisfy the $n_s$ and $r$ observational constraints but can be made viable with a significant contribution from what we call a savior curvaton, a large $\;f_{\rm NL}^{\rm (loc)}$ is inevitable. On the other hand, when the underlying inflation model already satisfies the $n_s$ and $r$ observational constraints, so significant curvaton contribution is forbidden, a large $\;f_{\rm NL}^{\rm (loc)}$ is possible in the exceptional case when the isocurvature fluctuation in the curvaton fluid is much greater than the global curvature fluctuation.

astro-ph.CO↗

arXiv2022

TF08 Snowmass Report: BSM Model Building

We summarize the state of Beyond the Standard Model (BSM) model building in particle physics for Snowmass 2021, focusing mainly on several whitepaper contributions to BSM model building (TF08) and closely related areas.

hep-ph↗

arXiv2022

BCFT in a Black Hole Background: An Analytical Holographic Model

We study the entanglement phase structure of a holographic boundary conformal field theory (BCFT) in a two-dimensional black hole background. The bulk dual is the AdS$_3$ black string geometry with a Karch-Randall brane. We compute the subregion entanglement entropy of various two-sided bipartitions to elucidate the phase space where a Page curve exists in this setup. We do fully analytical computations on both the gravity side and the field theory side and demonstrate that the results precisely match. We discuss the entanglement phase structure describing where a Page curve exists in this geometry in the context of these analytical results. This is a useful model to study entanglement entropy for quantum field theory on a curved background.

hep-th↗

arXiv2022

Effective Theory of Warped Compactifications and the Implications for KKLT

We argue that effective actions for warped compactifications can be subtle, with large deviations in the effective potential from naive expectations owing to constraint equations from the higher-dimensional metric. We demonstrate this deviation in a careful computation of the effective potential for the conifold deformation parameter of the Klebanov-Strassler solution. The uncorrected naive effective potential for the conifold was previously used to argue that the Klebanov-Strassler background would be destabilized by antibranes placed at the conifold infrared tip unless the flux was uncomfortably large. We show this result is too strong because the formerly neglected constraint equations eliminate the features of the potential that allowed for the instability in the de Sitter uplift of the KKLT scenario.

hep-th↗

arXiv2022

Jackiw-Teitelboim Gravity from the Karch-Randall Braneworld

In this letter, we show that Jackiw-Teitelboim (JT) gravity can be naturally realized in the Karch-Randall braneworld. Notably the role of the dilaton in JT gravity is played by the radion in a suitably orbifolded version of the setup. In the classical entanglement entropy calculation, there is an apparent degeneracy of Ryu-Takayanagi surfaces. We demonstrate how quantum fluctuations of the radion/dilaton resolves this would-be classical puzzle regarding entanglement wedge reconstruction.

hep-th↗

arXiv2022

New Horizons for Fundamental Physics with LISA

The Laser Interferometer Space Antenna (LISA) has the potential to reveal wonders about the fundamental theory of nature at play in the extreme gravity regime, where the gravitational interaction is both strong and dynamical. In this white paper, the Fundamental Physics Working Group of the LISA Consortium summarizes the current topics in fundamental physics where LISA observations of GWs can be expected to provide key input. We provide the briefest of reviews to then delineate avenues for future research directions and to discuss connections between this working group, other working groups and the consortium work package teams. These connections must be developed for LISA to live up to its science potential in these areas.

gr-qc↗