Phenomenological Signatures Research Articles

Primordial Black Holes from Null Energy Condition Violation during Inflation.

Primordial black holes (PBHs) and the violation of the null energy condition (NEC) have significant implications for our understanding of the very early Universe. We present a novel approach to generate PBHs via the NEC violation in a single-field inflationary scenario. In our scenario, the Universe transitions from a first slow-roll inflation stage with a Hubble parameter H=H_{inf1} to a second slow-roll inflation stage with H=H_{inf2}≫H_{inf1}, passing through an intermediate stage of NEC violation. The NEC violation naturally enhances the primordial scalar power spectrum at a certain wavelength, leading to the production of PBHs with masses and abundances of observational interest. We also investigate the phenomenological signatures of scalar-induced gravitational waves resulting from the enhanced density perturbations. Our work highlights the potential of utilizing a combination of PBHs, scalar-induced gravitational waves, and primordial gravitational waves as a valuable probe for studying NEC violation during inflation, opening up new avenues for exploring the early Universe.

Density dependent displaced vertex signatures as a novel probe of light dark sector scalars at the LHC

Dynamical theories of dark energy predict new degrees of freedom with particular environmental sensitivity to avoid constraints on fifth forces. We show that the similar, yet complementary multi-purpose detector setup of the ATLASand CMS experiments provides a unique opportunity to place sensitivity on such scenarios in a narrow, yet relevant parameter range. Furthermore, our investigation gives rise to a novel phenomenological signature that the LHC experimentscan pursue to exploit their complementary detector design from a BSM perspective.

Dark matter bound-state formation in the Sun

The Sun may capture asymmetric dark matter (DM), which can subsequently form bound-states through the radiative emission of a sub-GeV scalar. This process enables generation of scalars without requiring DM annihilation. In addition to DM capture on nucleons, the DM-scalar coupling responsible for bound-state formation also induces capture from self-scatterings of ambient DM particles with DM particles already captured, as well as with DM bound-states formed in-situ within the Sun. This scenario is studied in detail by solving Boltzmann equations numerically and analytically. In particular, we take into consideration that the DM self-capture rates require a treatment beyond the conventional Born approximation. We show that, thanks to DM scatterings on bound-states, the number of DM particles captured increases exponentially, leading to enhanced emission of relativistic scalars through bound-state formation, whose final decay products could be observable. We explore phenomenological signatures with the example that the scalar mediator decays to neutrinos. We find that the neutrino flux emitted can be comparable to atmospheric neutrino fluxes within the range of energies below one hundred MeV. Future facilities like Hyper-K, and direct DM detection experiments can further test such scenario.

Core and halo properties in multi-field wave dark matter

In this work, we compute multi-field core and halo properties in wave Dark Matter models. We focus on the case where Dark Matter consists of two light (real) scalars, interacting gravitationally. As in the single-field Ultra Light Dark Matter (ULDM) case, the scalar field behaves as a coherent BEC with a definite ground state (at fixed total mass), often referred to in the literature as a gravitational soliton. We establish an efficient algorithm to find the ground and excited states of such two-field systems. We then use simulations to investigate the gravitational collapse and virialization, starting from different initial conditions, into solitons and surrounding halo. As in the single-field case, a virialized halo forms with a gravitational soliton (ground state) at the center. We find some evidence for an empirical relation between the soliton mass and energy and those of the host halo. We use this to then find a numerical relation between the properties of the two. Finally, we use this to address the issue of alleviating some of the tensions that single-field ULDM has with observational data, in particular, the issue of how a galaxy's core and radius are related. We find that if galaxies of different masses have similar percentages of the two species, then the core-radius scaling tension is not addressed. However, more general possibilities occur if the relative abundance of species in each halo correlates with the total mass of the galaxy. If this is the case, the model predicts several other phenomenological signatures.

Spatial diffusion of heavy quarks in a background magnetic field

The ratio of shear viscosity to entropy density shows a valley-shaped pattern well-known in the community of heavy-ion physics. Diffusion coefficients of heavy quark and meson show a similar structure, and both sketches have become quite popular in the community. Present work has attempted a finite magnetic field extension of the diffusion coefficients of heavy quark and meson. Using Einstein's diffusion relation, we calculated heavy quark and heavy meson diffusion by the ratio of conductivity to susceptibility in the kinetic theory framework of relaxation time approximation. The relaxation time of heavy quark and meson are tuned from the knowledge of earlier works on spatial diffusion estimations, and then we have extended the framework for a finite magnetic field, where our outcomes have revealed two aspects—anisotropic and quantum aspects of diffusion with future possibilities of phenomenological signature. Published by the American Physical Society 2024

Probing light fermiophobic Higgs boson via diphoton jets at the HL-LHC

In this study, we explore the phenomenological signatures associated with a light fermiophobic Higgs boson, hf, within the type-I two-Higgs-doublet model at the HL-LHC. Our meticulous parameter scan illuminates an intriguing mass range for mhf, spanning [1,10] GeV. This mass range owes its viability to substantial parameter points, largely due to the inherent challenges of detecting the soft decay products of hf at contemporary high-energy colliders. Given that this light hf ensures Br(hf→γγ)≃1, Br(H±→hfW±)≃1, and MH±≲330 GeV, we propose a golden discovery channel: pp→hfH±→γγγγℓ±ν, where ℓ± includes e± and μ±. However, a significant obstacle arises as the two photons from the hf decay mostly merge into a single jet due to their proximity within ΔR<0.4. This results in a final state characterized by two jets, rather than four isolated photons, thus intensifying the QCD backgrounds. To tackle this, we devise a strategy within to identify jets with two leading subparticles as photons, termed diphoton jets. Our thorough detector-level simulations across 18 benchmark points predominantly show signal significances exceeding the 5σ threshold at an integrated luminosity of 3 ab−1. Furthermore, our approach facilitates accurate mass reconstructions for both mhf and MH±. Notably, in the intricate scenarios with heavy charged Higgs bosons, our application of machine learning techniques provides a significant boost in significance. Published by the American Physical Society 2024

Quantum gravity phenomenology from the perspective of quantum general relativity and quadratic gravity

Multi-messenger astronomy provides us with the possibility of discovering phenomenological signatures of quantum-gravity effects. This should be of paramount importance in the pursuit of an elusive quantum theory for the gravitational interactions. Here we discuss feasible explorations within the effective field theory (EFT) treatment of general relativity. By exploring current techniques borrowed from modern amplitude methods, we calculate leading quantum corrections to the classical radiated momentum and spectral waveforms. The lessons drawn from these low-energy results are that phenomenological applications in gravitational-wave physics can be discussed in line with the EFT approach. In turn, we also examine possible phenomenological surveys from the perspective of a UV completion for quantum gravity which employs the metric as the fundamental dynamical variable, namely quadratic gravity. Being more specific, by resorting to the eikonal approximation, we compute the leading-order time delay/advance in the scattering of light by a heavy object and find a possible significant deviation from the standard general-relativity prediction. This allows us to probe causal uncertainty due to quantum fluctuations of the gravitational field as a genuine prediction from Planck-scale physics.

Functional Connectivity of the Anterior Cingulate Cortex and the Right Anterior Insula Differentiates between Major Depressive Disorder, Bipolar Disorder and Healthy Controls.

Background: This study aimed to explore possible differences of the whole-brain functional connectivity of the anterior cingulate cortex (ACC) and anterior insula (AI), in a sample of depressed patients with major depressive disorder (MDD), bipolar disorder (BD) and healthy controls (HC). Methods: A hundred and three subjects (nMDD = 35, nBD = 25, and nHC = 43) between the ages of eighteen and sixty-five years old underwent functional magnetic resonance imaging. The CONN Toolbox was used to process and analyze the functional connectivity of the ACC and AI. Results: The comparison between the patients (MDD/BD) and HC yielded increased resting-state functional connectivity (rsFC) between the ACC and the motor and somatosensory cortices (SSC), superior parietal lobule (SPL), precuneus, and lateral occipital cortex, which was driven by the BD group. In addition, hyperconnectivity between the right AI and the motor and SSC was found in BD, as compared to HC. In MDD, as compared to HC, hyperconnectivity between ACC and SPL and the lateral occipital cortex was found, with no statistical rsFC differences for the AI seed. Compared to BD, the MDD group showed ACC-cerebellum hyperconnectivity and a trend for increased rsFC between the right AI and the bilateral superior frontal cortex. Conclusions: Considering the observed hyperconnectivity between the ACC/somatosensory cortex in the patient group, we suggest depression may be related to an impairment of the sensory-discriminative function of the SSC, which results in the phenomenological signature of mental pain in both MDD and BD. These findings suggest that future research should investigate this particular network with respect to motor functions and executive control, as a potential differential diagnostic biomarker for MDD and BD.

Primordial black holes and induced gravitational waves from double-pole inflation

The primordial black hole (PBH) productions from the inflationary potential with an inflection point usually rely heavily on the fine-tuning of the model parameters. We propose in this work a new kind of the α-attractor inflation with asymmetric double poles that naturally and easily lead to a period of non-attractor inflation, during which the PBH productions are guaranteed with less fine-tuning the model parameters. This double-pole inflation can be tested against the observational data in the future with rich phenomenological signatures: (1) the enhanced curvature perturbations at small scales admit a distinctive feature of ultraviolet oscillations in the power spectrum; (2) the quasi-monochromatic mass function of the produced PBHs can be made compatible to the asteroid-mass PBHs as the dominant dark matter component, the planet-mass PBHs as the OGLE ultrashort-timescale microlensing events, and the solar-mass PBHs as the LIGO-Virgo events; (3) the induced gravitational waves can be detected by the gravitational-wave detectors in space and Pulsar Timing Array/Square Kilometer Array.

Phenomenological signatures of gauge invariant theories of gravity with vectorial nonmetricity

In this paper, we discuss on the phenomenological footprints of gauge invariant theories of gravity where the gravitational effects are due not only to spacetime curvature, but also to vectorial nonmetricity. We explore the possibility that vectorial nonmetricity and gauge symmetry may survive after $SU(2)\ifmmode\times\else\texttimes\fi{}U(1)$ (electroweak) symmetry breaking, so that these may have impact on the explanation of certain cosmological puzzles, such as the nature of the dark matter and of the dark energy. We show that this is possible only for theories with gradient nonmetricity, i.e., when the vectorial nonmetricity amounts to a gradient of a scalar. The possibility that vectorial nonmetricity may have played a role in the quantum epoch is not ruled out. We also present an alternative interpretation of gauge invariance of theories with vectorial nonmetricity, which we call the ``many-worlds'' interpretation due to its overall similitude with the known interpretation of quantum physics.

Lepton-flavor-violating tau decays from triality

Motivated by flavour symmetry models, we construct theories based on a low-energy limit featuring lepton flavour triality that have the flavour-violating decays $\tau^\pm \to \mu^\pm \mu^\pm e^\mp$ and $\tau^\pm \to e^\pm e^\pm \mu^\mp$ as the main phenomenological signatures of physics beyond the standard model. These decay modes are expected to be probed in the near future with increased sensitivity by the Belle II experiment at the SuperKEKB collider. The simple standard model extensions featured have doubly-charged scalars as the mediators of the above decay processes. The phenomenology of these extensions is studied here in detail.

LHC signatures of τ-flavoured vector leptoquarks

We consider the phenomenological signatures of Simplified Models of Flavourful Leptoquarks, whose Beyond-the-Standard Model (SM) couplings to fermion generations occur via textures that are well motivated from a broad class of ultraviolet flavour models (which we briefly review). We place particular emphasis on the study of the vector leptoquark ∆μ with assignments (3,1, 2/3) under the SM’s gauge symmetry, SU(3)C× SU(2)L× U(1)Y, which has the tantalising possibility of explaining both {mathcal{R}}_{K^{left(ast right)}} and {mathcal{R}}_{D^{left(ast right)}} anomalies. Upon performing global likelihood scans of the leptoquark’s coupling parameter space, focusing in particular on models with tree-level couplings to a single charged lepton species, we then provide confidence intervals and benchmark points preferred by low (er)-energy flavour data. Finally, we use these constraints to further evaluate the (promising) Large Hadron Collider (LHC) detection prospects of pairs of τ-flavoured ∆μ, through their distinct (a)symmetric decay channels. Namely, we consider direct third-generation leptoquark and jets plus missing-energy searches at the LHC, which we find to be complementary. Depending on the simplified model under consideration, the direct searches constrain the ∆μ mass up to 1500-1770 GeV when the branching fraction of ∆μ is entirely to third-generation quarks (but are significantly reduced with decreased branching ratios to the third generation), whereas the missing-energy searches constrain the mass up to 1150-1700 GeV while being largely insensitive to the third-generation branching fraction.

Effective models of nonsingular quantum black holes

We investigate how the resolution of the singularity problem for the Schwarzschild black hole could be related to the presence of quantum gravity effects at horizon scales. Motivated by the analogy with the cosmological Schwarzschild-de Sitter solution, we construct a broad class of nonsingular, static, asymptotically flat black-hole solutions with a de Sitter (dS) core, sourced by an anisotropic fluid, which effectively encodes the quantum corrections. The latter are parametrized by a single length-scale $\ensuremath{\ell}$, which has a dual interpretation as an effective ``quantum hair'' and as the length-scale resolving the classical singularity. Depending on the value of $\ensuremath{\ell}$, these solutions can have two horizons, be extremal (when the two horizons merge) or be horizonless exotic stars. We also investigate the thermodynamic behavior of our black-hole solutions and propose a generalization of the area law in order to account for their entropy. We find a second-order phase transition near extremality, when $\ensuremath{\ell}$ is of order of the classical Schwarzschild radius ${R}_{\mathrm{S}}$. Black holes with $\ensuremath{\ell}\ensuremath{\sim}{R}_{\mathrm{S}}$ are thermodynamically preferred with respect to those with $\ensuremath{\ell}\ensuremath{\ll}{R}_{\mathrm{S}}$, supporting the relevance of quantum corrections at horizon scales. We also find that the extremal configuration is a zero-temperature, zero-entropy state with its near-horizon geometry factorizing as ${\mathrm{AdS}}_{2}\ifmmode\times\else\texttimes\fi{}{\mathrm{S}}^{2}$, signalizing the possible relevance of these models for the information paradox. Finally, we show that the presence of quantum corrections with $\ensuremath{\ell}\ensuremath{\sim}{R}_{\mathrm{S}}$ have observable phenomenological signatures in the photon orbits and in the quasinormal modes (QNMs) spectrum. In particular, in the near-extremal regime, the imaginary part of the QNMs spectrum scales with the temperature as ${c}_{1}/\ensuremath{\ell}+{c}_{2}\ensuremath{\ell}{T}_{\mathrm{H}}^{2}$, while it goes to zero linearly in the near-horizon limit. Our general findings are confirmed by revisiting two already known models, which are particular cases of our general class of models, namely the Hayward and Gaussian-core black holes.

Comprehensive study of the light charged Higgs boson in the type-I two-Higgs-doublet model

In the type-I two-Higgs-doublet model, existing theoretical and experimental constraints still permit the light charged Higgs boson with a mass below the top quark mass. We present a complete roadmap for the light charged Higgs boson at the LHC through the comprehensive phenomenology study, focusing on the normal scenario where the lighter \textit{CP}-even Higgs boson is the observed Higgs boson. In type-I, it is challenging to simultaneously accommodate the light mass of the charged Higgs boson and the constraints from theory, electroweak precision data, Higgs data, $b\to s \gamma$, and direct search bounds. Consequently, the parameter space is extremely curtailed, which predicts somewhat definite phenomenological signatures. We find that the mass of the pseudoscalar Higgs boson, $M_A$, is the most crucial factor in the phenomenology of the charged Higgs boson. If $M_A$ is light, the charged Higgs boson decays mainly into $A W^\pm$. When $M_A$ is above the $A W^\pm$ threshold, the dominant decay mode is into $ \tau^\pm \nu$. Over the whole viable parameter space, we study all the possible production and decay modes of charged Higgs bosons at the LHC, and suggest three efficient channels: (i) $pp \to H^+ H^-\to [\tau \nu] [\tau \nu]$; (ii) $pp \to HA/HH/AA \to H^\pm W^\mp H^\pm W^\mp \to [\tau \nu] [\tau \nu] W W$; (iii) $pp \to H^+ H^-\to [b \bar b W ] [b \bar b W ] $. Based on the sophisticated signal-background analyses including detector simulation, we showed that the significance of the first final state is large, that of the second one is marginal around three, but the third one suffers from huge $t\bar t$ related backgrounds.

On the Inner Horizon Instability of Non-Singular Black Holes

Regular black holes represent a conservative model in which the classical singularity is replaced by a non-singular core without necessarily modifying the spacetime outside the trapping horizon. Given the possible lack of phenomenological signatures, it is crucial to study the consistency of the model. In this short work, we review the physical mechanism leading to the instability of the central core, arguing that that non-perturbative backreation is non-negligible and must be taken into account to provide a meaningful description of physical black holes.

The Aha! moment: Is insight a different form of problem solving?

In everyday life, we mainly solve problems with a conscious solution search (non-insight). However, sometimes a perplexing problem is resolved by a quantum leap in understanding. This phenomenon is known as the Aha! experience (insight). Although insight has a distinct phenomenological and behavioral signature, its driving mechanism remains debated. Weisberg (2015) proposed an integrated theory of insight arguing that insight, like non-insight, mainly depends on conscious, cognitive operations with restructuring as a distinguishing feature of insight. However, only if those operations lead to an impasse, insight is achieved through unconscious processes. We assessed some of the premises of this theory by asking participants (N = 42) to solve 70 word puzzles (CRAT) that can either be solved with insight or non-insight. For each puzzle, participants indicated word puzzle difficulty, solution confidence, solution suddenness, and the experiences of impasse and restructuring. As expected, participants reported higher suddenness of and confidence in insight solutions than non-insightful ones. Surprisingly, we could not corroborate the otherwise consistently reported higher solution accuracy and faster solution speed for insight. Crucially, as suggested by the integrated theory of insight, impasse was not a prerequisite for insight to occur. Although restructuring, indeed, preceded insight solutions more often, it seemed a more general problem-solving skill also applied for non-insight solutions. Moreover, early on, participants reported an increased experience of problem difficulty for puzzles later solved with insight. This ability to report on the solution search of insight demonstrates that, as proposed by the theory, insight involves conscious, cognitive operations.

String Theory, the Dark Sector, and the Hierarchy Problem

We discuss dark energy, dark matter and the hierarchy problem in the context of a general non-commutative formulation of string theory. In this framework dark energy is generated by the dynamical geometry of the dual spacetime while dark matter, on the other hand, comes from the degrees of freedom dual to the visible matter. This formulation of string theory is sensitive both to the IR and UV scales and the Higgs scale is radiatively stable by being a geometric mean of radiatively stable UV and IR scales. We also comment on various phenomenological signatures of this novel approach to dark energy, dark matter and the hierarchy problem. We find that this new view on the hierarchy problem is realized in a toy model based on a non-holomorphic deformation of the stringy cosmic string. Finally, we discuss a proposal for a new non-perturbative formulation of string theory, which sheds light on M theory and F theory, as well as on supersymmetry and holography.

Distinguishing inert Higgs doublet and inert triplet scenarios

In this article we consider a comparative study between Type-I 2HDM and Y=0, SU(2) triplet extensions having one Z_2-odd doublet and triplet that render the desired dark matter(DM). For the inert doublet model (IDM) either a neutral scalar or pseudoscalar can be the DM, whereas for inert triplet model (ITM) it is a CP-even scalar. The bounds from perturbativity and vacuum stability are studied for both the scenarios by calculating the two-loop beta functions. While the quartic couplings are restricted to 0.1-0.2 for a Planck scale perturbativity for IDM, these are much relaxed (0.8 ) for ITM. The RG-improved potentials by Coleman-Weinberg show the regions of stability, meta-stability and instability of the electroweak vacuum. The constraints coming from DM relic, the direct and indirect experiments like XENON1T, LUX and H.E.S.S., Fermi-LAT allow the DM mass gtrsim 700, ,1176 GeV for IDM, ITM respectively. Though mass-splitting among Z_2-odd particles in IDM is a possibility for ITM we have to rely on loop-corrections. The phenomenological signatures at the LHC show that the mono-lepton plus missing energy with prompt and displaced decays in the case of IDM and ITM can distinguish such scenarios at the LHC along with other complementary modes.

Gauge-invariant bounce from loop quantum gravity

We present a gauge-invariant treatment of singularity resolution using loop quantum gravity techniques with respect to local SU(2) transformations. Our analysis reveals many novel features of quantum geometry which were till now hidden in models based on non-gauge-invariant discretizations. Quantum geometric effects resolve the big bang singularity replacing it with a non-singular bounce when spacetime curvature reaches Planckian value. The bounce is found to be generically asymmetric in the sense that pre-bounce and post-bounce branches are not mirrored to each other and effective constants, such as Newton’s constant, are rescaled across the bounce. Furthermore, in the vicinity of the bounce, minimally coupled matter behaves as non-minimally coupled. These ramifications of quantum geometry open a rich avenue for potential phenomenological signatures.

Examining the Discriminant Validity of Complex Posttraumatic Stress Disorder and Borderline Personality Disorder Symptoms: Results From a United Kingdom Population Sample.

Complex posttraumatic stress disorder (CPTSD) was added to the diagnostic nomenclature in the 11th revision of the International Classification of Diseases (ICD-11). Although considerable evidence exists supporting the construct validity of CPTSD, the distinguishability of CPTSD symptoms from those of borderline personality disorder (BPD) has been questioned. The present study examined the discriminant validity of CPTSD and BPD symptoms among a trauma-exposed population sample from the United Kingdom (N = 546). Participants completed self-report measures of CPTSD and BPD symptoms, and their latent structure was assessed using exploratory structural equation modeling (ESEM). A three-factor model with latent variables reflecting PTSD, disturbances in self-organization (DSO), and BPD symptoms provided the best fit of the data, χ2 (399, N = 546) = 1,650, p < .001; CFI = .944; TLI = .930; RMSEA = .077, 90% CI [.073, .081]. We identified multiple symptoms distinctive to individual constructs (e.g., disturbed relationships and suicidality) as well as symptoms shared across the constructs (e.g., affective dysregulation). The PTSD, β = .24; DSO, β = .23; and BPD, β = .27, latent variables were positively and significantly associated with childhood interpersonal trauma. The current findings support the discriminant validity of CPTSD and BPD symptoms and highlight various phenomenological signatures of each construct as well as demonstrate how these constructs share important similarities in symptom composition and exogenous correlates.