We consider K-mouflage models, which are K-essence theories coupled to matter. We analyze their quantum properties and in particular the quantum corrections to the classical Lagrangian. We setup the renormalization program for these models and show that, contrary to renormalizable field theories where renormalization by infinite counterterms can be performed in one step, K-mouflage theories involve a recursive construction whereby each set of counterterms introduces new divergent quantum contributions which in turn must be subtracted by new counterterms. This tower of counterterms can be in principle constructed step by step by recursion and allows one to calculate the finite renormalized action of the model. In particular, it can be checked that the classical action is not renormalized and that the finite corrections to the renormalized action contain only higher-derivative operators. We concentrate then on the regime where calculability is ensured, i.e., when the corrections to the classical action are negligible. We establish an operational criterion for classicality and show that this is satisfied in cosmological and astrophysical situations for (healthy) K-mouflage models which pass the solar system tests. These results rely on perturbation theory around a background and are only valid when the background configuration is quantum stable. We analyze the quantum stability of astrophysical and cosmological backgrounds and find that models that pass the solar system tests are quantum stable. We then consider the possible embedding of the K-mouflage models in an UV completion. We find that the healthy models which pass the solar system tests all violate the positivity constraint which would follow from the unitarity of the putative UV completion, implying that these healthy K-mouflage theories have no UV completion. We then analyze their behavior at high energy, and we find that the classicality criterion is satisfied in the vicinity of a high-energy collision, implying that the classical K-mouflage theory can be applied in this context. Moreover, the classical description becomes more accurate as the energy increases, in a way compatible with the classicalization concept.

We investigate the particle production due to parametric resonances in a model of inflation where the lightest composite state stemming from the minimal walking technicolor theory plays the role of the inflaton. For this model of inflation, the effective theory couples nonminimally to gravity. Regarding the preheating, we study in detail a model of a composite inflaton field $\varphi$ coupled to another scalar field $\chi$ with the interaction term $g^2{\varphi }^2{\chi }^2$. Particularly, in Minkowski space, the stage of parametric resonances can be described by the Mathieu equation. Interestingly, we discover that broad resonances can be typically achieved and are potentially efficient in our model causing the particle number density in this process to exponentially increase.

We discuss the consequences of assuming that the (Majorana) neutrino mass matrix $M_{\nu }$ and the charged lepton mass matrix $M_l$ satisfy $S_{\nu }^T{M}_{\nu }{S}_{\nu }=-M_{\nu }$ and $T_l^{†}{M}_l{M}_l^{†}{T}_l=M_l{M}_l^{†}$ with respect to some discrete groups $S_{\nu }$ and $T_l$ contained in $A_5$. These assumptions lead to a neutrino mass spectrum with two degenerate and one massless neutrino and also constrain mixing among them. We derive possible mixing patterns following from the choices $S_{\nu }=Z_2$, $Z_2\times Z_2$, and $T_l=Z_2,Z_2\times Z_2,Z_3,Z_5$ as subgroups of $A_5$. One predicts the maximal atmospheric neutrino mixing angle ${\theta }_{23}$ and $\mu \text{−}\tau$ reflection symmetry in a large number of cases, but it is also possible to obtain nonmaximal values for ${\theta }_{23}$. Only the third column of the neutrino mixing matrix can be obtained at the leading order due to degeneracy in masses of two of the neutrinos. We take up a specific example within the $A_5$ group and identify Higgs vacuum expectation values which realize the above assumptions. Nonleading terms present in this example are shown to lead to splitting among degenerate pairs and a consistent description of both neutrino masses and mixing angles.

We investigate the discovery potential of singly produced top-philic resonances at the high luminosity (HL) LHC in the four-top final state. Our analysis spans over the fully hadronic, semileptonic, and same-sign dilepton channels where we present concrete search strategies adequate to a boosted kinematic regime and high jet-multiplicity environments. We utilize the template overlap method with newly developed template observables for tagging boosted top quarks, a large-radius jet variable $M_J$, and customized $b$-tagging tactics for background discrimination. Our results show that the same-sign dilepton channel gives the best sensitivity among the considered channels, with an improvement of significance up to 10%–20% when combined with boosted top-tagging. Both the fully hadronic and semileptonic channels yield comparable discovery potential and contribute to further enhancements in the sensitivity by combining all channels. Finally, we show the sensitivity of a top-philic resonance at the LHC and HL-LHC by showing the $2\sigma$ exclusion limit and $5\sigma$ discovery reach, including a combination of all three channels.

We study the stability of hexaquark systems containing two heavy quarks and four light quarks within a simple quark model. No bound or metastable state is found. The reason stems from a delicate interplay between chromoelectric and chromomagnetic effects. Our calculation also provides information about anticharmed pentaquarks that are seemingly unbound in simple quark models.

We investigate the role of heavy quarks in the production of light flavored hadrons and in the determination of the corresponding nonperturbative hadronization probabilities. We define a general mass variable flavor number scheme for fragmentation functions that accounts for heavy quark mass effects, and perform a global QCD analysis to an up-to-date data set including very precise Belle and BABAR results. We show that the mass dependent picture provides a much more accurate and consistent description of the data.

We study the gauged ${\mathrm{U}(1)}_{\mathrm{B}–\mathrm{L}}$ extensions of the models for neutrino masses and dark matter. In this class of models, tiny neutrino masses are radiatively induced through the loop diagrams, while the origin of the dark matter stability is guaranteed by the remnant of the gauge symmetry. Depending on how the lepton number conservation is violated, these models are systematically classified. We present complete lists for the one-loop ${\mathbb{Z}}_2$ and the two-loop ${\mathbb{Z}}_3$ radiative seesaw models as examples of the classification. The anomaly cancellation conditions in these models are also discussed.

We investigate the potential of the long-baseline Deep Underground Neutrino Experiment (DUNE) to study large-extra-dimension (LED) models originally proposed to explain the smallness of neutrino masses by postulating that right-handed neutrinos, unlike all standard model fermion fields, can propagate in the bulk. The massive Kaluza-Klein (KK) modes of the right-handed neutrino fields modify the neutrino oscillation probabilities and can hence affect their propagation. We show that, as far as DUNE is concerned, the LED model is indistinguishable from a ($3+3N$)-neutrino framework for modest values of $N$; $N=1$ is usually a very good approximation. Nonetheless, there are no new sources of $CP$-invariance violation other than one $CP$-odd phase that can be easily mapped onto the $CP$-odd phase in the standard three-neutrino paradigm. We analyze the sensitivity of DUNE to the LED framework and explore the capability of DUNE to differentiate the LED model from the three-neutrino scenario and from a generic ($3+1$)-neutrino model.

We study planar Aharony-Bergman-Jafferis-Maldacena (ABJM) theory in a limit where one coupling is negligible compared to the other. We provide a recipe for exactly solving the expectation value of bosonic Bogomol’nyi-Prasad-Sommerfield (BPS) Wilson loops on arbitrary smooth contours, or the leading divergence for cusped ones, using results from localization. As an application, we compute the exact (generalized) cusp anomalous dimension and Bremsstrahlung function and use it to determine the interpolating $h$-function. We finally prove a conjecture on the exact form of the dilatation operator in a closed sector, hinting at the integrability of this limit.

The Ernst formulation of the Einstein equations is generalized to accommodate $f(R)$ theories of gravity. It is shown that, as in general relativity, the axisymmetric $f(R)$ field equations for a vacuum spacetime that is either stationary or cylindrically symmetric reduce to a single, nonlinear differential equation for a complex-valued scalar function. As a worked example, we apply the generalized Ernst equations to derive a $f(R)$ generalization of the Zipoy-Voorhees metric, which may be used to describe the gravitational field outside of an ellipsoidal neutron star. We also apply the theory to investigate the phase speed of large-amplitude gravitational waves in $f(R)$ gravity in the context of solitonlike solutions that display shock-wave behavior across the causal boundary.

We revisit the constraints on the small scale density perturbations ($10^4{\mathrm{Mpc}}^{-1}\lesssim k\lesssim 10^5{\mathrm{Mpc}}^{-1}$) from the modification of the freeze-out value of the neutron-proton ratio at the big-bang nucleosynthesis era. Around the freeze-out temperature $T\sim 0.5\mathrm{MeV}$, the universe can be divided into several local patches that have different temperatures since any perturbation that enters the horizon after the neutrino decoupling has not diffused yet. Taking account of this situation, we calculate the freeze-out value in detail. We find that the small scale perturbations decrease the $n$-$p$ ratio in contrast to previous works. With the use of the latest observed ${}^4\mathrm{He}$ abundance, we obtain the constraint on the power spectrum of the curvature perturbations as ${\mathrm{\Delta }}_{\mathcal{R}}^2\lesssim 0.018$ on $10^4{\mathrm{Mpc}}^{-1}\lesssim k\lesssim 10^5{\mathrm{Mpc}}^{-1}$.

It has become standard practice to take the logarithmic growth of the scale factor as a measure of the amount of inflation, despite the well-known fact that this is only an approximation for the true amount of inflation required to solve the horizon and flatness problems. The aim of this work is to show how this approximation can be completely avoided using an alternative framework for inflation model building. We show that using the inverse Hubble radius, $\mathcal{H}=aH$, as the key dynamical parameter, the correct number of $e$-folding arises naturally as a measure of inflation. As an application, we present an interesting model in which the entire inflationary dynamics can be solved analytically and exactly, and, in special cases, reduces to the familiar class of power-law models.

We determine the forecast errors on the absolute neutrino mass scale and the equation of state of dark energy by combining synthetic data from the Dark Energy Survey (DES) and the cosmic microwave background Planck surveyor. We use angular clustering of galaxies for DES in seven redshift shells up to $z\sim 1.7$ including cross-correlations between different redshift shells. We study models with massless and massive neutrinos and three different dark energy models: $\mathrm{\Lambda }$ cold dark matter (CDM) ($w=-1$), $w\mathrm{CDM}$ (constant $w$), and $w_a\mathrm{CDM}$ [evolving equation of state parameter $w(a)=w_0+w_a(1-a)$]. We include the impact of uncertainties in modeling galaxy bias using a constant and a redshift-evolving bias model. For the $\mathrm{\Lambda }\mathrm{CDM}$ model we obtain an upper limit for the sum of neutrino masses from $\mathrm{DES}+\text{Planck}$ of $\mathrm{\Sigma }{m}_{\nu }<0.08\mathrm{eV}$ (95% C.L.) for a fiducial mass of $\mathrm{\Sigma }{m}_{\nu }=0.047\mathrm{eV}$, with a $1\sigma$ error of 0.02 eV, assuming perfect knowledge of galaxy bias. For the $w\mathrm{CDM}$ model the limit is $\mathrm{\Sigma }{m}_{\nu }<0.10\mathrm{eV}$. For a $w\mathrm{CDM}$ model where galaxy bias evolves with redshift, the upper limit on the sum of neutrino masses increases to 0.29 eV. DES will be able to place competitive upper limits on the sum of neutrino masses of 0.1–0.3 eV and could therefore strongly constrain the inverted mass hierarchy of neutrinos. In a $w\mathrm{CDM}$ model the $1\sigma$ error on constant $w$ is $\mathrm{\Delta }w=0.03$ from DES galaxy clustering and Planck. Allowing $\mathrm{\Sigma }{m}_{\nu }$ as a free parameter increases the error on $w$ by a factor of 2, with $\mathrm{\Delta }w=0.06$. In a $w_a\mathrm{CDM}$ model, in which the dark energy equation of state varies with time, the errors are $\mathrm{\Delta }{w}_0=0.2$ and $\mathrm{\Delta }{w}_a=0.42$. Including neutrinos and redshift-dependent galaxy bias increases the errors to $\mathrm{\Delta }{w}_0=0.39$ and $\mathrm{\Delta }{w}_a=0.99$.

We show that if a spectator linear isocurvature dark matter field degree of freedom has a constant mass through its entire evolution history, the maximum measurable isocurvature spectral index that is consistent with the current tensor-to-scalar ratio bound of about $r\lesssim 0.1$ is about $n_I\lesssim 2.4$, even if experiments can be sensitive to a ${10}^{-6}$ contamination of the predominantly adiabatic power spectrum with an isocurvature power spectrum at the shortest observable length scales. Hence, any foreseeable future measurement of a blue isocurvature spectral index larger than $\sim 2.4$ may provide nontrivial evidence for dynamical degrees of freedom with time-dependent masses during inflation. The bound is not sensitive to the details of the reheating scenario and can be made mildly smaller if $r$ is better constrained in the future.

We set the first upper limit on the stochastic gravitational wave (GW) background in the frequency range of 1–5 Hz using a torsion-bar antenna (TOBA). A TOBA is a GW detector designed for the detection of low frequency GWs on the ground, with two orthogonal test masses rotated by the incident GWs. We performed a 24-hour observation run using the TOBA and set upper limits, based on frequentist statistics and Bayesian statistics. The most stringent values are ${\mathrm{\Omega }}_{\mathrm{gw}}{h}_0^2\le 6.0\times 10^{18}$ (frequentist) and ${\mathrm{\Omega }}_{\mathrm{gw}}{h}_0^2\le 1.2\times 10^{20}$ (Bayesian) both at 2.58 Hz, where $h_0$ is the Hubble constant in units of $100\mathrm{km}/\mathrm{s}/\mathrm{Mpc}$ and ${\mathrm{\Omega }}_{\mathrm{gw}}$ is the GW energy density per logarithmic frequency interval in units of the closure density.

Inspired by the tachyon-free nonsupersymmetric heterotic $\mathrm{SO}(16)\times \mathrm{SO}(16)$ string we consider a special class of nonsupersymmetric field theories: those that can be obtained from supersymmetric field theories by supersymmetry-breaking twists. We argue that such theories, like their supersymmetric counterparts, may still possess some fermionic symmetries as leftovers of the supergauge transformations and have special one-loop nonrenormalization properties due to holomorphicity. In addition, we extend the supergraph techniques to these theories to calculate some explicit supersymmetry-breaking corrections.

We study the prospects for probing a gauge singlet scalar-driven strong first-order electroweak phase transition with a future proton-proton collider in the 100 TeV range. Singlet-Higgs mixing enables resonantly enhanced di-Higgs production, potentially aiding discovery prospects. We perform Monte Carlo scans of the parameter space to identify regions associated with a strong first-order electroweak phase transition, analyze the corresponding di-Higgs signal, and select a set of benchmark points that span the range of di-Higgs signal strengths. For the $b\overline{b}\gamma \gamma$ and $4\tau$ final states, we investigate discovery prospects for each benchmark point for the high-luminosity phase of the Large Hadron Collider and for a future $pp$ collider with $\sqrt{s}=50$, 100, or 200 TeV. We find that any of these future collider scenarios could significantly extend the reach beyond that of the high-luminosity LHC, and that with $\sqrt{s}=100\mathrm{TeV}$ (200 TeV) and $30{\mathrm{ab}}^{-1}$, the full region of parameter space favorable to strong first-order electroweak phase transitions is almost fully (fully) discoverable.

The neutral component of a real pseudoscalar electroweak (EW) triplet can produce a diphoton excess at 750 GeV, if it is somewhat mixed with an EW singlet pseudoscalar. This triplet-singlet mixing allows for greater freedom in the diboson branching ratios than the singlet-only case, but it is still possible to probe the parameter space extensively with $300{\mathrm{fb}}^{-1}$. The charged component of the triplet is pair produced at the LHC, which results in a striking signal in the form of a pair of $W\gamma$ resonances with an irreducible rate of 0.27 fb. Other signatures include multiboson final states from cascade decays of the triplet-singlet neutral states. A large class of composite models feature both EW singlet and triplet pseudo-Nambu-Goldstone bosons in their spectrum, with the diboson couplings generated by axial anomalies.

The recent observation by the D0 collaboration of a narrow structure $X(5568)$ consisting of four different quark flavors $bdus$, has not been confirmed by LHCb. In the tightly bound diquark model, we estimate the lightest $bdus$, $0^{+}$ tetraquark at a mass of about 5770 MeV, approximately 200 MeV above the reported $X(5568)$, and just 7 MeV below the $B\overline{K}$ threshold. The charged tetraquark is accompanied by $I=1$ and $I=0$ neutral partners almost degenerate in mass. A $bdus$, $S$-wave, $1^{+}$ quartet at 5820 MeV is implied as well. In the charm sector, $cdus$, $0^{+}$ and $1^{+}$ tetraquarks are predicted at 2365 and 2501 MeV, about 40–50 MeV heavier than $D_{s0}(2317)$ and $D_{s1}(2460)$. The $bdus$ tetraquarks can be searched in the hadronic debris of a jet initiated by a $b$. However, some of them may also be produced in $B_c$ decays, $B_c\to X_{b0}+\pi$ with the subsequent decays $X_{b0}\to B_s+\pi$, giving rise to final states such as $B_s{\pi }^{+}{\pi }^0$. We also emphasize the importance of $B_c$ decays as a source of bound hidden charm tetraquarks, such as $B_c\to X(3872)+\pi$.

The parton distribution functions (PDFs) of the proton are one of the essential ingredients to describe physics processes at hadron colliders. The $Z$ boson production data at the LHC have a potential to constrain PDFs, especially the gluon distribution. In this study the CMS measurement of the inclusive double differential $Z$ boson production cross section in terms of transverse momentum and rapidity is compared to the next-to-leading order theory predictions at the center-of-mass energy, $\sqrt{s}=8\mathrm{TeV}$ with an integrated luminosity of $19.71{\mathrm{fb}}^{-1}$. In addition, the sensitivity of this measurement to PDFs is studied within the framework of the HERAFitter. A moderate improvement to the gluon distribution is observed at the Bjorken $x\approx 0.1$ region. However, in order to obtain further improvement to the gluon distribution in the global fits, the higher-order theory calculations accessible via fast techniques are necessary.