We study the influence of the fluctuations of a Lorentz-invariant and conserved vacuum on cosmological metric perturbations, and show that they generically blow up in the IR. We compute this effect using the Källén-Lehmann spectral representation of stress correlators in generic quantum field theories, as well as the holographic bound on their entanglement entropy, both leading to an IR cutoff that scales as the fifth power of the highest UV scale (in Planck units). One may view this as analogous to the Heisenberg uncertainty principle, which is imposed on the phase space of gravitational theories by the Einstein constraint equations. The leading effect on cosmological observables comes from anisotropic vacuum stresses which imply: i) any extension of the standard model of particle physics can only have masses (or resonances) $\lesssim 24\mathrm{TeV}$, and ii) perturbative quantum field theory or quantum gravity become strongly coupled beyond a UV scale of $\mathrm{\Lambda }\lesssim 1\mathrm{PeV}$. Such a low strong coupling scale is independently motivated by the Higgs hierarchy problem. This result, which we dub the cosmological nonconstant problem, can be viewed as an extension of the cosmological constant (CC) problem, demonstrating the nontrivial UV-IR coupling and (yet another) limitation of effective field theory in gravity. However, it is more severe than the old CC problem, as vacuum fluctuations cannot be tuned to cancel due to the positivity of spectral densities or entropy. We thus predict that future advances in cosmological observations and collider technology will sandwich from above and below, and eventually discover, new (nonperturbative) physics beyond the standard model within the TeV–PeV energy range.

We propose new large field inflation scenarios built on the framework of F-term axion monodromy. Our setup is based on string compactifications where D-branes create potentials for closed string axions via F-terms. Because the source of the axion potential is different from the standard sources of moduli stabilization, it is possible to lower the inflaton mass as compared to other massive scalars. We discuss a particular class of models based on type IIA flux compactifications with D6-branes. In the small field regime they describe supergravity models of quadratic chaotic inflation with a stabilizer field. In the large field regime the inflaton potential displays a flattening effect due to Planck suppressed corrections, allowing us to easily fit the cosmological parameters of the model within current experimental bounds.

There are indications of a possible breakdown of the standard model, suggesting that $\tau$ lepton interactions violate flavor universality, particularly through $B$ meson decays. BABAR, Belle, and LHCb report high ratios of $B\to D^{(*)}\tau \nu$. There are long-standing excesses in $B\to \tau \nu$ and $W\to \tau \nu$ decays and a deficit in inclusive $\tau$ to strange decays. We investigate whether two Higgs doublet models with the most general allowed couplings to quarks, and a large coupling to $\tau$ leptons, can explain these anomalies while respecting other flavor constraints and technical naturalness. Fits to $B\to D^{(*)}\tau \nu$ data require couplings of the new Higgs doublet to down-type quarks, opening the door to many highly constrained flavor-changing neutral current processes. We confront these challenges by introducing a novel ansatz that relates the new up- and down-type Yukawa couplings, and demonstrate viable values of the couplings that are free from fine-tuning. LEP and LHC searches for new Higgs bosons decaying via $H^0\to {\tau }^{+}{\tau }^{-}$ and $H^{\pm }\to {\tau }^{\pm }\nu$ allow a window of masses $m_H=[100–125]\mathrm{GeV}$ and $m_{\pm }\sim 100\mathrm{GeV}$ that is consistent with the predictions of our model. Contamination of the $W^{+}\to {\tau }^{+}\nu$ signal by $H^{+}\to {\tau }^{+}\nu$ decays at LEP could explain the apparent $W\to \tau \nu$ excess. We predict that the branching ratio for $B_s\to {\tau }^{+}{\tau }^{-}$ is not far below its current limit of several percent. An alternative model with decays of $B\to D^{(*)}\tau {\nu }_s$ to a sterile neutrino is also argued to be viable.

The condensation of scalar bilinear in a classically scale invariant strongly interacting hidden sector is used to generate the electroweak scale, where the excitation of the condensate is identified as dark matter. We formulate an effective theory for the condensation of the scalar bilinear and find in the self-consistent mean field approximation that the dark matter mass is of $O(1)\mathrm{TeV}$ with the spin-independent elastic cross section off the nucleon slightly below the LUX upper bound.

We derive the complete set of continuous maximal symmetries for standard model (SM) alignment that may occur in the tree-level scalar potential of multi-Higgs doublet models, with $n>2$ Higgs doublets. Our results generalize the symmetries of SM alignment, without decoupling of large mass scales or fine-tuning, previously obtained in the context of two-Higgs doublet models.

Measurement of $Z$ bosons produced in association with charm jets $(Zc)$ in proton-proton collisions in the forward region provides a direct probe of a potential nonperturbative (intrinsic) charm component in the proton wave function. We provide a detailed study of the potential to measure $Zc$ production at the LHCb experiment in Runs 2 and 3 of the LHC. The sensitivity to valence-like (sea-like) intrinsic charm is predicted to be $⟨x{⟩}_{\mathrm{IC}}\gtrsim 0.3\%(1\%)$. The impact of intrinsic charm on Higgs production at the LHC, including $Hc$, is also discussed in detail.

The azimuthal asymmetry in the risetime of signals in Auger surface detector stations is a source of information on shower development. The azimuthal asymmetry is due to a combination of the longitudinal evolution of the shower and geometrical effects related to the angles of incidence of the particles into the detectors. The magnitude of the effect depends upon the zenith angle and state of development of the shower and thus provides a novel observable, $(\sec \theta {)}_{\max }$, sensitive to the mass composition of cosmic rays above $3\times {10}^{18}\mathrm{eV}$. By comparing measurements with predictions from shower simulations, we find for both of our adopted models of hadronic physics (QGSJETII-04 and EPOS-LHC) an indication that the mean cosmic-ray mass increases slowly with energy, as has been inferred from other studies. However, the mass estimates are dependent on the shower model and on the range of distance from the shower core selected. Thus the method has uncovered further deficiencies in our understanding of shower modeling that must be resolved before the mass composition can be inferred from $(\sec \theta {)}_{\max }$.

We have measured the muon flux and production rate of muon-induced neutrons at a depth of 611 m water equivalent. Our apparatus comprises three layers of crossed plastic scintillator hodoscopes for tracking the incident cosmic-ray muons and 760 L of a gadolinium-doped liquid scintillator for producing and detecting neutrons. The vertical muon intensity was measured to be $I_{\mu }=(5.7\pm 0.6)\times {10}^{-6}{\mathrm{cm}}^{-2}{\mathrm{s}}^{-1}{\mathrm{sr}}^{-1}$. The yield of muon-induced neutrons in the liquid scintillator was determined to be $Y_n=(1.19\pm 0.08(\text{stat})\pm 0.21(\text{syst}))\times {10}^{-4}\mathrm{neutrons}/(\mu ·\mathrm{g}·{\mathrm{cm}}^{-2})$. A fit to the recently measured neutron yields at different depths gave a mean muon energy dependence of ${⟨E_{\mu }⟩}^{0.76\pm 0.03}$ for liquid-scintillator targets.

A new set of measurements of the top quark mass are presented, based on the proton-proton data recorded by the CMS experiment at the LHC at $\sqrt{s}=8\mathrm{TeV}$ corresponding to a luminosity of $19.7{\mathrm{fb}}^{-1}$. The top quark mass is measured using the $\text{lepton}+\text{jets}$, all-jets and dilepton decay channels, giving values of $172.35\pm 0.16(\mathrm{stat})\pm 0.48(\mathrm{syst})\mathrm{GeV}$, $172.32\pm 0.25(\mathrm{stat})\pm 0.59(\mathrm{syst})\mathrm{GeV}$, and $172.82\pm 0.19(\mathrm{stat})\pm 1.22(\mathrm{syst})\mathrm{GeV}$, respectively. When combined with the published CMS results at $\sqrt{s}=7\mathrm{TeV}$, they provide a top quark mass measurement of $172.44\pm 0.13(\mathrm{stat})\pm 0.47(\mathrm{syst})\mathrm{GeV}$. The top quark mass is also studied as a function of the event kinematical properties in the $\text{lepton}+\text{jets}$ decay channel. No indications of a kinematic bias are observed and the collision data are consistent with a range of predictions from current theoretical models of $t\overline{t}$ production.

Using a unified approach, we study the entropy of extremal black holes through the entropy of an electrically charged thin shell. We encounter three cases in which a shell can be taken to its own gravitational or horizon radius and become an extremal spacetime. In case 1, we use a nonextremal shell, calculate all the thermodynamic quantities including the entropy, take it to the horizon radius, and then take the extremal limit. In case 2, we take the extremal limit and the horizon radius limit simultaneously; i.e., as the shell approaches its horizon radius, it also approaches extremality. In case 3, we take first an extremal shell, and then take its horizon radius. We find that the thermodynamic quantities, in general, have different expressions in the three different cases. The entropy is the Bekenstein-Hawking entropy $S=A_{+}/4$ (where $A_{+}$ is the horizon area) in cases 1 and 2, and in case 3 it can be any well-behaved function of $A_{+}$. The contributions from the various thermodynamic quantities for the entropy in all three cases are distinct. Indeed, in cases 1 and 2, the limits agree in what concerns the entropy but they disagree in the behavior of all other thermodynamic quantities. Cases 2 and 3 disagree in what concerns the entropy but agree in the behavior of the local temperature and electric potential. Case 2 is, in a sense, intermediate between cases 1 and 3. Our approach sheds light on the extremal black hole entropy issue.

We obtain a point-separated noise kernel for the Reissner-Nordström metric. The noise kernel defines the fluctuations of the quantum stress tensor and is of central importance to semiclassical stochastic gravity. The metric is modeled as gravitationally collapsing spacetime, by using suitable coordinate transformations, defined earlier. The fluctuations of the quantum stress tensor, at the final stage of collapse, are then analyzed for both the naked singularity and black hole end states. The behavior of this noise kernel, at the Cauchy horizon (CH) for naked singularity, shows markedly different behavior from the self-similar Tolman-Bondi metric, which was obtained earlier. In the latter a very unique divergence was seen, which does not appear for the Reissner-Nordström metric here. It is known that the quantum stress tensor itself diverges at the CH for both of these metrics. In contrast, it can now be seen that the fluctuations of the stress tensor behave differently for the two cases. We give a discussion and further directions for investigations of this interesting behavior in the two cases (regarding the collapse scenario).

Herein we explore the possibility of explaining a gamma-ray excess in the Galactic Center with the dark matter scenario. After taking into account the constraints from both the AMS-02 experiment and the gamma-ray observation on dwarf spheroidal satellite galaxies in Fermi-LAT, we find that the $\tau$ lepton channel is the only permissive channel for the interpretation of the Galaxy center excess. Tau leptophilic dark matter provides a well-motivated framework in which the dark matter can dominantly couple to $\tau$ lepton at tree-level. We describe the interactions with a general effective field theory approach by using higher-dimensional operators, and this approach provides for a model independent analysis. We consider the constraints from the measurement of the DM relic density in the Planck experiment and the AMS-02 cosmic rays experiment, and find that most of the interaction operators except ${\mathcal{O}}_7$, ${\mathcal{O}}_9$ and ${\mathcal{O}}_{12}$ have been excluded. Due to the quantum fluctuations, even in such a scenario there are loop induced dark matter-nucleon interactions. We calculate the dark matter-nucleon scattering cross-section at loop-level, and if the limits on the dark matter-nucleon scattering cross-section from direct detection experiments are also taken into account, we find that the operators remaining available for accounting for the Galaxy center excess are ${\mathcal{O}}_9$ and ${\mathcal{O}}_{12}$.

An ultralight axion around $10^{-23}\mathrm{eV}$ is known as a viable dark matter candidate. A distinguished feature of such a dark matter is the oscillating pressure which produces the oscillation of the gravitational potential with frequency in the nano-Hz range. Recently, Khmelnitsky and Rubakov pointed out that this time dependent potential induces the pulse arrival residual and could be observed by the Square Kilometre Array (SKA) experiment. In this paper, we study the detectability of the oscillating pressure of the axion in the framework of $f(R)$ theory, and show that the amplitude of the gravitational potential can be enhanced or suppressed compared to that in Einstein’s theory depending on the parameters of the $f(R)$ model and mass of the axion. In particular, we investigate the Hu-Sawicki model and find the condition that the Hu-Sawicki model is excluded.

We study an $s$-channel resonance $R$ as a viable candidate to fit the diboson excess reported by ATLAS. We compute the contribution of the $\sim 2\mathrm{TeV}$ resonance $R$ to semileptonic and leptonic final states at the 13 TeV LHC. To explain the absence of an excess in the semileptonic channel, we explore the possibility where the particle $R$ decays to additional light scalars $X$, $X$ or $X$, $Y$. A modified analysis strategy has been proposed to study the three-particle final state of the resonance decay and to identify decay channels of $X$. Associated production of $R$ with gauge bosons has been studied in detail to identify the production mechanism of $R$. We construct comprehensive categories for vector and scalar beyond-standard-model particles which may play the role of particles $R$, $X$, $Y$ and find alternate channels to fix the new couplings and search for these particles.

At the LHC, an effective theory of the Higgs sector allows us to analyze kinematic distributions in addition to inclusive rates, although there is no clear hierarchy of scales. We systematically analyze how well dimension-6 operators describe LHC observables in comparison to the full theory, and in a range where the LHC will be sensitive. The key question is how the breakdown of the dimension-6 description affects Higgs measurements during the upcoming LHC run for weakly interacting models. We cover modified Higgs sectors with a singlet and doublet extension, new top partners, and a vector triplet. First, weakly interacting models only generate small relevant subsets of dimension-6 operators. Second, the dimension-6 description tends to be justified at the LHC. Scanning over model parameters, significant discrepancies can nevertheless arise; their main source is the matching procedure in the absence of a well-defined hierarchy of scales. While these issues require vigilance, they should not present a major problem for future LHC analyses.

A very plausible explanation for the recently observed diphoton excess at the 13 TeV LHC is a (pseudo)scalar with mass around 750 GeV, which couples to a gluon pair and to a photon pair through loops involving vectorlike quarks (VLQs). To accommodate the observed rate, the required Yukawa couplings tend to be large. A large Yukawa coupling would rapidly run up with the scale and quickly reach the perturbativity bound, indicating that new physics, possibly with a strong dynamics origin, is nearby. The case becomes stronger especially if the ATLAS observation of a large width persists. In this paper we study the implication on the scale of new physics from the 750 GeV diphoton excess using the method of renormalization group running with careful treatment of different contributions and perturbativity criterion. Our results suggest that the scale of new physics is generically not much larger than the TeV scale, in particular if the width of the hinted (pseudo)scalar is large. Introducing multiple copies of VLQs, lowering the VLQ masses, and enlarging VLQ electric charges help reduce the required Yukawa couplings and can push the cutoff scale to higher values. Nevertheless, if the width of the 750 GeV resonance turns out to be larger than about 1 GeV, it is very hard to increase the cutoff scale beyond a few TeVs. This is a strong hint that new particles in addition to the 750 GeV resonance and the vectorlike quarks should be around the TeV scale.

We investigate the symmetry property and construct the wave function of the dibaryon states containing two strange quarks with $S=0$ in both the flavor SU(3) symmetric and breaking cases. We discuss how the color $\otimes$ isospin $\otimes$ spin states of dibaryon in the symmetry broken case of flavor SU(3) can be extracted from the fully antisymmetric states in flavor SU(3). The stability of the dibaryon against the strong decay into two baryons is then discussed, by using the variational method within a constituent quark model with confining and color-spin interactions. To compare our results with those from lattice QCD in the flavor SU(3) limit, we search for the stable H-dibaryon in a wide range of $\pi$ meson masses. We find that with the given potential, there is no compact six-quark dibaryon state in the SU(3) flavor symmetry broken case with realistic quark masses as well as in the flavor SU(3) symmetric case in a wide range of quark masses.

We study $U_A(1)$ symmetry and its relation to chiral symmetry at finite temperature through the application of the functional renormalization group to the $SU(3)$ quark-meson model. Very different from the mass gap and mixing angel between $\eta$ and ${\eta }^{\prime }$ mesons, which are defined at the mean-field level and behavior like condensates, the topological susceptibility includes a fluctuation-induced part which becomes dominant at high temperature. As a result, the $U_A(1)$ symmetry is still considerably broken in the chiral symmetry restoration phase.