Extra Sector Research Articles

Cosmological solution through gravitational decoupling in [formula omitted] gravity

This paper aims to formulate anisotropic cosmological solution of a non-static spherical structure with the help of gravitational decoupling scheme through minimal geometric deformation in f(G,T) gravity. This technique transforms only the radial metric function while the temporal component remains unchanged. Consequently, the field equations are separated into two independent arrays: one is related to the seed source and the other characterizes the extra sector. In order to derive the solution corresponding to the isotropic sector, we use the Friedmann–Lemaitre–Robertson–Walker cosmic model and employ the barotropic equation of state as well as power-law model. Finally, we study the impact of decoupling parameter to describe different eras of the universe through graphical analysis. It is found that physically viable and stable trends of the resulting solution are achieved for both radiation-dominated as well as matter-dominated epochs in this modified theory.

Purely virtual extension of quantum field theory for gauge invariant fields: quantum gravity

Quantum gravity is extended to include purely virtual “cloud sectors”, which allow us to define a complete set of point-dependent observables, including a gauge invariant metric and gauge invariant matter fields, and calculate their off-shell correlation functions perturbatively. The ordinary on-shell correlation functions and the S matrix elements are unaffected. Each extra sector is made of a cloud field, its anticommuting partner, a “cloud-fixing” function and a cloud Faddeev-Popov determinant. The additional fields are purely virtual, to ensure that no ghosts propagate. The extension is unitary. In particular, the off-shell, diagrammatic version of the optical theorem holds. The one-loop two-point functions of dressed scalars, vectors and gravitons are calculated. Their absorptive parts are positive, cloud independent and gauge independent, while they are unphysical if non purely virtual clouds are used. We illustrate the differences between our approach to the problem of finding a complete set of observables in quantum gravity and other approaches available in the literature.

Charged anisotropic solutions through decoupling in f(G,T) gravity

This paper formulates two charged interior anisotropic spherical solutions through extended gravitational decoupling scheme in the context of [Formula: see text] theory, where [Formula: see text] and [Formula: see text] symbolize the Gauss–Bonnet term and trace of the stress–energy tensor, respectively. The inclusion of an extra sector in the isotropic domain results in the production of anisotropy in the inner geometry. This technique splits the field equations into two independent arrays by deforming the temporal and radial metric coefficients, giving rise to the seed and extra fluid distributions, respectively. The Krori–Barua metric potentials are used to calculate solution of the first set, while some constraints are used to solve the unknowns present in the second array. The resulting anisotropic solution is a combination of both the obtained solutions. We inspect the influence of charge as well as decoupling parameter on the physical variables and anisotropic factor. Finally, the viability and stability of the developed solutions are checked by energy conditions and stability criteria, respectively. We conclude that the first solution is viable as well as stable for the particular range of the decoupling parameter, whereas the second solution is viable but not stable.

Extra W-boson mass from a D3-brane

Motivated by the recent CDF measurement of the W-boson mass, we study string-based particle physics models which can accommodate this deviation from the Standard Model. We consider an F-theory GUT in which the visible sector is realized on intersecting 7-branes, and extra sector states arise from a probe D3-brane near an E-type Yukawa point. The D3-brane worldvolume naturally realizes a strongly coupled sector which mixes with the Higgs. In the limit where some extra sector states get their mass solely from Higgs vevs, this leads to a contribution to the ρ parameter which is too large, but as the D3-brane is separated from the 7-brane stack, this effect is suppressed, leading to O(1) - O(10) TeV scale extra sector states and a correction to ρ which would be in accord with the CDF result. We also estimate the contribution to the oblique electroweak parameter S, and find that it is compatible with existing constraints. This also leads to additional signatures, including diphoton resonances (as well as other diboson final states) in the O(1) - O(10) TeV range.

CFTs blueshift tensor fluctuations universally

The strong constraints of conformal symmetry cause any nearly-conformal sector to blueshift tensor fluctuations in cosmology. Hidden sectors with approximate conformal symmetry, which may be quite large, are a well-motivated extension of physics beyond the Standard Models of particle physics and cosmology. They can therefore lead to a detectable shift in the tensor tilt for next-generation CMB and gravitational wave experiments. We compute the leading-order contribution to the in-in graviton two-point function from virtual loops in such sectors to demonstrate this universal effect. In units where a single conformally-coupled scalar is 1, limits from Stage-IV CMB experiments could bound the size of this extra sector to be smaller than ∼1015, under a plausible calculational assumption backed by a simple power counting argument. This would be sufficient to rule out N-Naturalness as a complete resolution of the hierarchy problem.

Toverline{T} -deformed fermionic theories revisited

We revisit Toverline{T} deformations of d = 2 theories with fermions with a view toward the quantization. As a simple illustration, we compute the deformed Dirac bracket for a Majorana doublet and confirm the known eigenvalue flows perturbatively. We mostly consider those Toverline{T} theories that can be reconstructed from string-like theories upon integrating out the worldsheet metric. After a quick overview of how this works when we add NSR-like or GS-like fermions, we obtain a known non-supersymmetric Toverline{T} deformation of a mathcal{N} = (1, 1) theory from the latter, based on the Noether energy-momentum. This world- sheet reconstruction implies that the latter is actually a supersymmetric subsector of a d = 3 GS-like model, implying hidden supercharges, which we do construct explicitly. This brings us to ask about different Toverline{T} deformations, such as manifestly supersymmetric Toverline{T} and also more generally via the symmetric energy-momentum. We show that, for theories with fermions, such choices often lead us to doubling of degrees of freedom, with potential unitarity issues. We show that the extra sector develops a divergent gap in the “small deformation” limit and decouples in the infrared, although it remains uncertain in what sense these can be considered a deformation.

Statistical coupling constants from hidden sector entanglement

String theory predicts that the couplings of nature descend from dynamical fields. All known string-motivated particle physics models also come with a wide range of possible extra sectors. It is common to posit that such moduli are frozen to a background value, and that extra sectors can be nearly completely decoupled. Performing a partial trace over all sectors other than the visible sector generically puts the visible sector in a mixed state, with coupling constants drawn from a quantum statistical ensemble. An observable consequence of this entanglement between visible and extra sectors is that the reported values of couplings will appear to have an irreducible variance. Including this variance in fits to experimental data gives an important additional parameter that can be used to distinguish this scenario from the case where couplings are treated as fixed parameters. There is a consequent interplay between energy range and precision of an experiment that allows an extended reach for new physics.

Signatures of dark Higgs boson in light fermionic dark matter scenarios

Thermal dark matter scenarios based on light (sub-GeV) fermions typically require the presence of an extra dark sector containing both a massive dark photon along with a dark Higgs boson. The latter typically generates both the dark photon mass and an additional mass term for the dark sector fermions. This simple setup has both rich phenomenology and bright detection prospects at high-intensity accelerator experiments. We point out that in addition to the well studied pseudo-Dirac regime, this model can achieve the correct relic density in three different scenarios, and examine in details their properties and experimental prospects. We emphasize in particular the effect of the dark Higgs boson on both detection prospects and cosmological bounds.

From 6D superconformal field theories to dynamic gauged linear sigma models

Compactifications of 6D superconformal field theories (SCFTs) on four-manifolds generate a large class of novel 2d quantum field theories. We consider in detail the case of the rank one simple non-Higgsable cluster 6D SCFTs. On the tensor branch of these theories, the gauge group is simple and there are no matter fields. For compactifications on suitably chosen Kahler surfaces, we present evidence that this provides a method to realize 2d SCFTs with N = (0,2) supersymmetry. In particular, we find that reduction on the tensor branch of the 6D SCFT yields a description of the same 2d fixed point that is described in the UV by a gauged linear sigma model (GLSM) in which the parameters are promoted to dynamical fields, that is, a "dynamic GLSM" (DGLSM). Consistency of the model requires the DGLSM to be coupled to additional non-Lagrangian sectors obtained from reduction of the anti-chiral two-form of the 6D theory. These extra sectors include both chiral and anti-chiral currents, as well as spacetime filling non-critical strings of the 6D theory. For each candidate 2d SCFT, we also extract the left- and right-moving central charges in terms of data of the 6D SCFT and the compactification manifold.

Symmetric and asymmetric reheating

We study models in which the inflaton is coupled to two otherwise decoupled sectors, and the effect of preheating and related processes on their energy densities during the evolution of the universe. Over most of parameter space, preheating is not disrupted by the presence of extra sectors, and even comparatively weakly coupled sectors can get an order 1 fraction of the total energy at this time. If two sectors are both preheated, the high number densities could also lead to inflaton mediated thermalisation. If only one sector is preheated, Bose enhancement of the late time inflaton decays may cause significant deviations from the perturbative prediction for their relative reheat temperatures. Meanwhile, in Non-Oscillatory inflation models resonant effects can result in exponentially large final temperature differences between sectors that have similar couplings to the inflaton. Asymmetric reheating is potentially relevant for a range of beyond the Standard Model physics scenarios. We show that in dark matter freeze-in models, hidden sector temperatures a factor of 10 below that of the visible sector are typically needed for the relic abundance to be set solely by freeze-in dynamics.

No-go theorem for fully supersymmetric GUTs with metastable supersymmetry breaking

We introduce fully SGUTs, SUSY grand unified theories that, upon symmetry breaking through the Higgs mechanism, decompose into a visible sector and an extra sector where the dynamics of the extra sector gauge group is responsible for SUSY breaking. Fully SGUTs thus have the important feature that all gauge groups of the visible sector and the extra sector unify into a simple gauge group at the SGUT scale, therefore generalizing the successful MSSM gauge coupling unification to all the gauge couplings of the theory. By focusing on the ISS SUSY-breaking mechanism in the extra sector, we show that it is impossible to reproduce the MSSM matter content when there exists a metastable ISS SUSY-breaking state.

Kinetic mixing at strong coupling

A common feature of many string-motivated particle physics models is additional strongly coupled U(1)'s. In such sectors, electric and magnetic states have comparable mass, and integrating out modes also charged under U(1) hypercharge generically yields CP preserving electric kinetic mixing and CP violating magnetic kinetic mixing terms. Even though these extra sectors are strongly coupled, we show that in the limit where the extra sector has approximate N = 2 supersymmetry, we can use formal methods from Seiberg-Witten theory to compute these couplings. We also calculate various quantities of phenomenological interest such as the cross section for scattering between visible sector states and heavy extra sector states, as well as the effects of supersymmetry breaking induced from coupling to the MSSM.

Lorentzian proper vertex amplitude: Classical analysis and quantum derivation

Spin foam models, an approach to defining the dynamics of loop quantum gravity, make use of the Plebanski formulation of gravity, in which gravity is recovered from a topological field theory via certain constraints called simplicity constraints. However, the simplicity constraints in their usual form select more than just one gravitational sector as well as a degenerate sector. This was shown, in previous work, to be the reason for the "extra" terms appearing in the semiclassical limit of the Euclidean EPRL amplitude. In this previous work, a way to eliminate the extra sectors, and hence terms, was developed, leading to the what was called the Euclidean proper vertex amplitude. In the present work, these results are extended to the Lorentzian signature, establishing what is called the Lorentzian proper vertex amplitude. This extension is non-trivial and involves a number of new elements since, for Lorentzian bivectors, the split into self-dual and anti-self-dual parts, on which the Euclidean derivation was based, is no longer available. In fact, the classical parts of the present derivation provide not only an extension to the Lorentzian case, but also, with minor modifications, provide a new, more four dimensionally covariant derivation for the Euclidean case. The new elements in the quantum part of the derivation are due to the different structure of unitary representations of the Lorentz group.

750 GeV diphotons from a D3-brane

Motivated by the recently reported diphoton excess at 750 GeV observed by both CMS and ATLAS, we study string-based particle physics models which can accommodate this signal. Quite remarkably, although Grand Unified Theories in F-theory tend to impose tight restrictions on candidate extra sectors, the case of a probe D3-brane near an E-type Yukawa point naturally leads to a class of strongly coupled models capable of accommodating the observed signature. In these models, the visible sector is realized by intersecting 7-branes, and the 750 GeV resonance is a scalar modulus associated with motion of the D3-brane in the direction transverse to the Standard Model 7-branes. Integrating out heavy 3–7 string messenger states leads to dimension five operators for gluon fusion production and diphoton decays. Due to the unified structure of interactions, these models also predict that there should be additional decay channels to ZZ and Zγ. We also comment on models with distorted unification, where both the production mechanism and decay channels can differ.

Interpreting the CMSℓ+ℓ−jj+missing transverse energy excess with a leptoquark model

Motivated by excesses in $ee jj$ and $e\nu jj$ channels observed by the CMS collaboration, in 8 TeV LHC data, a model of lepto-quarks with mass around 500 GeV was proposed in the literature. In order to reproduce the claimed event rate, lepto-quarks were assumed to have a significant partial branching ratio into an extra sector, taken to be Dark Matter, other than the canonical $ej$. We here show that the decay channel of lepto-quark into Dark Matter can fit another excess claimed by CMS, in $\ell^+\ell^- jj E\!\!\!\!/_{\rm T}$: the event rate, the distribution in di-lepton invariant mass and the rapidity range are compatible with the data. We provide predictions for the forthcoming Run II of the 14 TeV LHC and discuss aspects of dark matter detection.

OPE methods for the holomorphic Higgs portal

We develop a systematic and general approach to study the effective Higgs Lagrangian in a supersymmetric framework in which the Higgs fields in the visible sector couple weakly to another sector. The extra sector may be strongly coupled in general. It is assumed to be superconformal in the ultraviolet, but develop a mass-gap with supersymmetry breaking in the infrared. The main technique used in our approach is that of the operator product expansion (OPE). By using OPE methods we are able to compute the parameters in the Higgs Lagrangian to quadratic order and make general statements that are applicable to many classes of models. Not only does this approach allow us to understand the traditional problems plaguing simple models from a different perspective, it also reveals new possibilities for solutions of these problems. The methods and results of our work should be useful in constructing a viable and natural model of physics beyond the Standard Model.

EFFECTS OF SECTOR AGGREGATION ON CO2 MULTIPLIERS IN MULTIREGIONAL INPUT–OUTPUT ANALYSES

The past few years have seen the emergence of several global multiregional input–output (MRIO) databases. Due to the cost and complexity of developing such extensive tables, industry sectors are generally represented at a rather aggregate level. Currently, one of the most important applications of input–output analysis is environmental assessments, for which highly aggregate sectors may not be sufficient to yield accurate results. We experiment with four of the most important global MRIO systems available, analyzing the sensitivity of a set of aggregate CO2 multipliers to aggregations in the MRIO tables used to calculate them. Across databases, we find (a) significant sensitivity to background system detail and (b) that sub-sectors contained within the same aggregate MRIO sector may exhibit highly different carbon multipliers. We conclude that the additional information provided by the extra sector detail may warrant the additional costs of compilation, due to the heterogeneous nature of economic sectors in terms of their environmental characteristics.

Oblique electroweak parametersSandTfor superconformal field theories

We develop a general set of methods for computing the oblique electroweak parameters S and T for bottom-up and top-down motivated scenarios in which the Higgs weakly mixes with a superconformal extra sector. In addition to their utility in phenomenological studies, the observables S and T are also of purely theoretical interest as they are defined by correlation functions of broken symmetries. We show that in the limit where the extra sector enjoys an approximate custodial symmetry, the leading contributions to S and T can be recast as calculable data of the theory in the conformal phase. Using this result, we also obtain model-independent bounds on the sign and size of oblique electroweak corrections from unitary superconformal theories.

The Higgs as a probe of supersymmetric extra sectors

We present a general method for calculating the leading contributions to h 0 → gg and h 0 → γγ in models where the Higgs weakly mixes with a nearly supersymmetric extra sector. Such mixing terms can play an important role in raising the Higgs mass relative to the value expected in the MSSM. Our method applies even when the extra sector is strongly coupled, and moreover does not require a microscopic Lagrangian description. Using constraints from holomorphy we fix the leading parametric form of the contributions to these Higgs processes, including the Higgs mixing angle dependence, up to an overall coefficient. Moreover, when the Higgs is the sole source of mass for a superconformal sector, we show that even this coefficient is often calculable. For appropriate mixing angles, the contribution of the extra states to h 0 → gg and h 0 → γγ can vanish. We also discuss how current experimental limits already lead to non-trivial constraints on such models. Finally, we provide examples of extra sectors which satisfy the requirements necessary to use the holomorphic approximation.

Classical and quantum wormholes in a 5D compact Kaluza–Klein theory

We study the classical and quantum euclidean wormholes for an empty (4+1) dimensional Kaluza–Klein universe with a positive cosmological constant and a spatially flat Robertson–Walker type metric. It is shown that classical wormholes do not exist neither for the space–time sector nor the extra dimensional sector of this model, but two spectra of quantum wormholes as the solutions of the Wheeler–DeWitt equation exist that are consistent with the Hawking–Page conjecture about the necessary boundary conditions. In the spectrum where the external scale factor R shapes the quantum wormholes the internal scale factor a may play the role of effective matter source, and in the spectrum where the internal scale factor a shapes the quantum wormholes the external scale factor R may play the role of effective matter source.