The emergent gravity paradigm interprets gravitational field equations as describing the thermodynamic limit of the underlying statistical mechanics of microscopic degrees of freedom of the spacetime. The connection is established by attributing a heat density $Ts$ to the null surfaces where $T$ is the appropriate Davies-Unruh temperature and $s$ is the entropy density. The field equations can be obtained from a thermodynamic variational principle which extremizes the total heat density of all null surfaces. The explicit form of $s$ determines the nature of the theory. We explore the consequences of this paradigm for an arbitrary null surface and highlight the thermodynamic significance of various geometrical quantities. In particular, we show that (a) a conserved current, associated with the time development vector in a natural fashion, has direct thermodynamic interpretation in all Lanczos-Lovelock models of gravity; (b) one can generalize the notion of gravitational momentum, introduced in T. Padmanabhan, [arXiv:1506.03814] to all Lanczos-Lovelock models of gravity such that the conservation of the total momentum leads to the relevant field equations; (c) the thermodynamic variational principle which leads to the field equations of gravity can also be expressed in terms of the gravitational momentum in all Lanczos-Lovelock models; and (d) three different projections of gravitational momentum related to an arbitrary null surface in the spacetime lead to three different equations, all of which have thermodynamic interpretation. The first one reduces to a Navier-Stokes equation for the transverse drift velocity. The second can be written as a thermodynamic identity $TdS=dE+PdV$. The third describes the time evolution of the null surface in terms of suitably defined surface and bulk degrees of freedom. The implications are discussed.

We study conservation laws for gravity theories invariant under general coordinate transformations. The class of models under consideration includes Einstein’s general relativity theory as a special case as well as its generalizations to non-Riemannian spacetime geometry and nonminimal coupling. We demonstrate that an arbitrary vector field on the spacetime manifold generates a current density that is conserved under certain conditions, and find the expression of the corresponding superpotential. For a family of models including nonminimal coupling between geometry and matter, we discuss in detail the differential conservation laws and the conserved quantities defined in terms of covariant multipole moments. We show that the equations of motion for the multipole moments of extended microstructured test bodies lead to conserved quantities that are closely related to the conserved currents derived in the field-theoretic framework.

We study the spin $1/2$ and spin $3/2$ fermion fields in a thick braneworld scenario in six dimensions called string-cigar model. This smooth stringlike model has a source that satisfies the dominant energy condition and undergoes a Ricci flow. We propose a new coupling for the fermions with a background gauge field which allows a smooth and normalized massless mode in the brane with positive tension. By numerical methods the mass spectrum and the massive eigenfunctions are obtained. The Kaluza-Klein massive tower exhibits the usual increasing pattern and, in this scenario, the coupling term does not allow tachyonic Kaluza-Klein states. The brane core and the background gauge field alter the properties of the massive KK tower, enhancing the amplitude of the massive states near the origin and changing the properties of the analogue Schrödinger potential. Furthermore, we find massive modes as resonant states in this scenario for both fermionic fields.

The cross-correlation of a foreground density field with two different background convergence fields can be used to measure cosmographic distance ratios and constrain dark energy parameters. We investigate the possibility of performing such measurements using a combination of optical galaxy surveys and neutral hydrogen (HI) intensity mapping surveys, with emphasis on the performance of the planned Square Kilometre Array (SKA). Using HI intensity mapping to probe the foreground density tracer field and/or the background source fields has the advantage of excellent redshift resolution and a longer lever arm achieved by using the lensing signal from high redshift background sources. Our results show that, for our best SKA-optical configuration of surveys, a constant equation of state for dark energy can be constrained to $\simeq 8\%$ for a sky coverage $f_{\mathrm{sky}}=0.5$ and assuming a $\sigma ({\mathrm{\Omega }}_{\mathrm{DE}})=0.03$ prior for the dark energy density parameter. We also show that using the cosmic microwave background as the second source plane is not competitive, even when considering a COrE-like satellite.

The evolution of the Universe between inflation and the onset of big bang nucleosynthesis is difficult to probe and largely unconstrained. This ignorance profoundly limits our understanding of dark matter: we cannot calculate its thermal relic abundance without knowing when the Universe became radiation dominated. Fortunately, small-scale density perturbations provide a probe of the early Universe that could break this degeneracy. If dark matter is a thermal relic, density perturbations that enter the horizon during an early matter-dominated era grow linearly with the scale factor prior to reheating. The resulting abundance of substructure boosts the annihilation rate by several orders of magnitude, which can compensate for the smaller annihilation cross sections that are required to generate the observed dark matter density in these scenarios. In particular, thermal relics with masses less than a TeV that thermally and kinetically decouple prior to reheating may already be ruled out by Fermi-LAT observations of dwarf spheroidal galaxies. Although these constraints are subject to uncertainties regarding the internal structure of the microhalos that form from the enhanced perturbations, they open up the possibility of using gamma-ray observations to learn about the reheating of the Universe.

Coalescing binaries of neutron stars and black holes are one of the most important sources of gravitational waves for the upcoming network of ground-based detectors. Detection and extraction of astrophysical information from gravitational-wave signals requires accurate waveform models. The effective-one-body and other phenomenological models interpolate between analytic results and numerical relativity simulations, that typically span $\mathcal{O}(10)$ orbits before coalescence. In this paper we study the faithfulness of these models for neutron star-black hole binaries. We investigate their accuracy using new numerical relativity (NR) simulations that span 36–88 orbits, with mass ratios $q$ and black hole spins ${\chi }_{\mathrm{BH}}$ of $(q,{\chi }_{\mathrm{BH}})=(7,\pm 0.4),(7,\pm 0.6)$, and $(5,-0.9)$. These simulations were performed treating the neutron star as a low-mass black hole, ignoring its matter effects. We find that (i) the recently published SEOBNRv1 and SEOBNRv2 models of the effective-one-body family disagree with each other (mismatches of a few percent) for black hole spins ${\chi }_{\mathrm{BH}}\ge 0.5$ or ${\chi }_{\mathrm{BH}}\le -0.3$, with waveform mismatch accumulating during early inspiral; (ii) comparison with numerical waveforms indicates that this disagreement is due to phasing errors of SEOBNRv1, with SEOBNRv2 in good agreement with all of our simulations; (iii) phenomenological waveforms agree with SEOBNRv2 only for comparable-mass low-spin binaries, with overlaps below 0.7 elsewhere in the neutron star-black hole binary parameter space; (iv) comparison with numerical waveforms shows that most of this model’s dephasing accumulates near the frequency interval where it switches to a phenomenological phasing prescription; and finally (v) both SEOBNR and post-Newtonian models are effectual for neutron star-black hole systems, but post-Newtonian waveforms will give a significant bias in parameter recovery. Our results suggest that future gravitational-wave detection searches and parameter estimation efforts would benefit from using SEOBNRv2 waveform templates when focused on neutron star-black hole systems with $q\lesssim 7$ and ${\chi }_{\mathrm{BH}}\approx [-0.9,+0.6]$. For larger black hole spins and/or binary mass ratios, we recommend the models be further investigated as NR simulations in that region of the parameter space become available.

We examine the usefulness of the unitarity conditions in a left-right symmetric model which can translate into giving a stronger constraint on the model parameters together with the criteria derived from vacuum stability and perturbativity. In this light, we demonstrate the bounds on the masses of the physical scalars present in the model and find the scenario where multiple scalar modes are in the reach of the Large Hadron Collider. We also analyze the additional conditions that can come from charge breaking minima in this context.

We present the calculation of the hyperon forward spin polarizability ${\gamma }_0$ using manifestly Lorentz-covariant baryon chiral perturbation theory including the intermediate contribution of the spin-$3/2$ states. As at the considered order the extraction of ${\gamma }_0$ is a pure prediction of chiral perturbation theory, the obtained values are a good test for this theory. After including explicitly the decuplet states, our SU(2) results have a very good agreement with the experimental data and we extend our framework to SU(3) to give predictions for the hyperons’ ${\gamma }_0$ values. Prominent are the ${\mathrm{\Sigma }}^{-}$ and ${\mathrm{\Xi }}^{-}$ baryons as their photon transition to the decuplet is forbidden in SU(3) symmetry and therefore they are not sensitive to the explicit inclusion of the decuplet in the theory.

Experiments aiming to detect coherent neutrino-nucleus scattering present opportunities to probe new light weakly coupled states, such as sub-GeV mass dark matter, in several extensions of the Standard Model. These states can be produced along with neutrinos in the collisions of protons with the target, and their production rate can be enhanced if there exists a light mediator produced on shell. We analyze the sensitivity reach of several proposed experiments to light dark matter interacting with the Standard Model via a light vector mediator coupled to the electromagnetic current. We also determine the corresponding sensitivity to massless singlet neutrino-type states with interactions mediated by the baryon number current. In both cases we observe that proposed coherent neutrino-nucleus scattering experiments, such as COHERENT at the spallation neutrino source (SNS) and CENNS at Fermilab, will have sensitivity well beyond the existing limits.

We perform global fits to the most recent data (after summer 2014) on Higgs boson signal strengths in the framework of the minimal supersymmetric standard model. We further impose the existing limits on the masses of charginos, staus, stops, and sbottoms together with the current Higgs mass constraint $|M_{H_1}-125.5\mathrm{GeV}|<6\mathrm{GeV}$. The heavy supersymmetric (SUSY) particles such as squarks enter into the loop factors of the $Hgg$ and $H\gamma \gamma$ vertices, while other SUSY particles such as sleptons and charginos also enter into that of the $H\gamma \gamma$ vertex. We also take into account the possibility of other light particles, such as other Higgs bosons and neutralinos, into which the 125.5 GeV Higgs boson can decay. We use the data from the ATLAS, CMS, and the Tevatron, with existing limits on SUSY particles, to constrain on the relevant SUSY parameters. We obtain allowed regions in the SUSY parameter space of squark, slepton and chargino masses, and the $\mu$ parameter. We find that $|\mathrm{\Delta }{S}^{\gamma }/S_{\mathrm{SM}}^{\gamma }|\lesssim 0.1$ at 68% confidence level when $M_{{\tilde{\chi }}_1^{\pm }}>300\mathrm{GeV}$ and $M_{{\tilde{\tau }}_1}>300\mathrm{GeV}$, irrespective of the squarks masses. Furthermore, $|\mathrm{\Delta }{S}^{\gamma }/S_{\mathrm{SM}}^{\gamma }|\lesssim 0.03$ when $M_{{\tilde{\chi }}_1^{\pm },{\tilde{\tau }}_1}>500\mathrm{GeV}$ and $M_{{\tilde{t}}_1,{\tilde{b}}_1}\gtrsim 600\mathrm{GeV}$.

We study the cold and dense regime in the phase diagram of two-color QCD with heavy quarks within a three-dimensional effective theory for Polyakov loops. This theory is derived from two-color QCD in a combined strong-coupling and hopping expansion. In particular, we study the onset of diquark density as the finite-density transition of the bosonic baryons in the two-color world. In contrast to previous studies of heavy dense QCD, our zero-temperature extrapolations are consistent with a continuous transition without binding energy. They thus provide evidence that the effective theory for heavy quarks is capable of describing the characteristic differences between diquark condensation in two-color QCD and the liquid-gas transition of nuclear matter in QCD.

Through the scattering of light-pseudoscalar mesons $(\pi ,K,\eta ,{\eta }^{\prime })$ off charmed mesons $(D,D_s)$, we study the $D_{s0}^{*}(2317)$ state and other relevant charm scalar mesons in a unitarized chiral effective field theory approach. We investigate the charm scalar meson poles with different strangeness ($S$) and isospin ($I$) quantum numbers as well as their corresponding residues, which provide the coupling strengths of the charm scalar mesons. Both the light-quark mass and $N_C$ dependences of the pole positions of the $D_{s0}^{*}(2317)$ and the poles with $(S,I)=(0,1/2)$ are analyzed in detail in this work. Interestingly we observe quite similar pion mass trajectories for the resonance pole at around 2.1 GeV with $(S,I)=(0,1/2)$ to those of the $f_0(500)$ given in the literature. When increasing the values of $N_C$ we find that a bound state and a virtual state in the $(S,I)=(1,0)$ channel asymmetrically approach the $DK$ threshold for $N_C<6$, and they meet at this threshold at $N_C=6$. When $N_C>6$, the bound and virtual states move into the complex plane on the second Riemann sheet and become a symmetric pair of resonance poles. For large enough values of $N_C$, neither the $D_{s0}^{*}(2317)$ pole nor the poles with $(S,I)=(0,1/2)$ tend to fall down to the real axis, indicating that they do not behave like a standard quark-antiquark meson at large $N_C$.

We study transverse momentum resummation for the azimuthal angular correlation in dijet production in hadron collisions based on the Collins-Soper-Sterman formalism. The complete one-loop calculations are carried out in the collinear framework for the differential cross sections at low imbalance transverse momentum between the two jets. Important cross-checks are performed to demonstrate that the soft divergences are canceled out between different diagrams and, in particular, for those associated with the final state jets. The leading and subleading logarithms are identified. All order resummation is derived following the transverse momentum dependent factorization at this order. Its phenomenological applications are also presented.

We show that the dominant channel proposed for the determination of the Higgs boson trilinear coupling, $pp\to HH+X$ via gluon fusion, exhibits an interference structure that is independent of the collider energy for collider energies in the range $8\mathrm{TeV}\le \sqrt{s}\le 100\mathrm{TeV}$ and is almost maximally destructive. This insensitivity to the collider energy remains approximately true for a variety of other two Higgs production mechanisms although the magnitude of the interference varies widely.

The search strategy or the discovery of new effects for heavy neutrinos often rely on their different decay channels to detectable particles. In particular, in this work we study the decay of a Majorana neutrino with interactions obtained from an effective general theory modeling new physics at the scale $\mathrm{\Lambda }$. The results obtained are general because they are based in an effective theory and not in specific models. We are interested in relatively light-heavy Majorana neutrinos, with masses lower than the $W$ mass ($m_N<m_W$). This mass range simplifies the study by reducing the possible decay modes. Moreover, we found that for $\mathrm{\Lambda }\sim 1\mathrm{TeV}$, the neutrino plus photon channel could account for different observations: we analyze the potentiality of the studied interactions to explain some neutrino-related problems like the MiniBooNE and SHALON anomalies. We show in different figures the dominant branching ratios and the decay length of the Majorana neutrino in this approach. These kinds of heavy neutral leptons could be searched for in the LHC with the use of displaced vertices techniques.

We present for the first time a detailed and comprehensive analysis of the experimental results that set the current world sensitivity limit on the magnitude of the electric dipole moment (EDM) of the neutron. We have extended and enhanced our earlier analysis to include recent developments in the understanding of the effects of gravity in depolarizing ultracold neutrons; an improved calculation of the spectrum of the neutrons; and conservative estimates of other possible systematic errors, which are also shown to be consistent with more recent measurements undertaken with the apparatus. We obtain a net result of $d_{\mathrm{n}}=-0.21\pm 1.82\times 10^{-26}e\mathrm{cm}$, which may be interpreted as a slightly revised upper limit on the magnitude of the EDM of $3.0\times 10^{-26}e\mathrm{cm}$ (90% C.L.) or $3.6\times 10^{-26}e\mathrm{cm}$ (95% C.L.).

We consider the relation between three physical problems: 2D directed lattice random walks, ensembles of $T_{n,n+1}$ torus knots, and instanton ensembles in 5D Super QED with one compact dimension in $\mathrm{\Omega }$-background and with 5D Chern-Simons term at the level one. All these ensembles exhibit the critical behavior typical for the “$\text{area}+\text{length}+\text{corners}$” statistics of grand ensembles of 2D directed paths. Using the combinatorial description, we obtain an explicit expression of the generating function for $q$-Narayana numbers which amounts to the new critical behavior in the ensemble of $T_{n,n+1}$ torus knots and in the ensemble of instantons in 5D SQED. Depending on the number of the nontrivial fugacities, we get either the critical point, or cascade of critical lines and critical surfaces. In the 5D gauge theory the phase transition is of the third order, while in the ensemble of paths and ensemble of knots it is typically of the first order. We also discuss the relation with the integrable models.

We study thermalization of strongly coupled gauge theory plasma in the presence of a magnetic field using the $\mathrm{AdS}/\mathrm{CFT}$ correspondence. We utilize the falling energy-shell model as a holographic description of gauge theory plasma undergoing thermalization, and find the effect of the magnetic field on thermalization time in various space-time dimensions. Our results demonstrate that the magnetic field universally hastens thermalization of strongly coupled gauge theory plasma.

We show that the forward limit of tree-level scattering equations with two massive particles yields the $\mathrm{SL}(2,\mathbb{C})$-covariant form of the one-loop scattering equations recently proposed by Geyer et al. We clarify several properties about these equations and the formulas at one loop. We then argue that in the bi-adjoint scalar theory, such a forward limit yields the correct one-loop massless amplitudes, which leads to a new formula for the latter.

Thermofield dynamics is presented in terms of a path integral using coherent states, equivalently, using a coadjoint orbit action. A field theoretic formulation in terms of fields on a manifold $\mathcal{M}\times \tilde{\mathcal{M}}$ where the two components have opposite orientation is also presented. We propose formulating gravitational dynamics for noncommutative geometry using thermofield dynamics, doubling the Hilbert space modeling the noncommutative space. We consider $2+1$ dimensions in some detail and since $\mathcal{M}$ and $\tilde{\mathcal{M}}$ have opposite orientation, the commutative limit leads to the Einstein-Hilbert action as the difference of two Chern-Simons actions.