It has been recently pointed out that by removing the axial symmetry in the “multi-angle effects” associated with the neutrino-neutrino interactions for supernova (SN) neutrinos a new multi-azimuthal-angle (MAA) instability would arise. In particular, for a flux ordering $F_{{\nu }_e}>F_{{\overline{\nu }}_e}>F_{{\nu }_x}$, as expected during the SN accretion phase, this instability occurs in the normal neutrino mass hierarchy. However, during this phase, the ordinary matter density can be larger than the neutrino one, suppressing the self-induced conversions. In this regard, we investigate the matter suppression of the MAA effects, performing a linearized stability analysis of the neutrino equations of motion, in the presence of realistic SN density profiles. We compare these results with the numerical solution of the SN neutrino nonlinear evolution equations. Assuming axially symmetric distributions of neutrino momenta, we find that the large matter term strongly inhibits the MAA effects. In particular, the hindrance becomes stronger including realistic forward-peaked neutrino angular distributions. As a result, in our model for a $10.8M_{\odot }$ iron-core SNe, MAA instability does not trigger any flavor conversion during the accretion phase. Instead, for a $8.8M_{\odot }$ O-Ne-Mg core SN model, with lower matter density profile and less forward-peaked angular distributions, flavor conversions are possible also at early times.

The T2K experiment has reported the first observation of the appearance of electron neutrinos in a muon neutrino beam. The main and irreducible background to the appearance signal comes from the presence in the neutrino beam of a small intrinsic component of electron neutrinos originating from muon and kaon decays. In T2K, this component is expected to represent 1.2% of the total neutrino flux. A measurement of this component using the near detector (ND280), located 280 m from the target, is presented. The charged current interactions of electron neutrinos are selected by combining the particle identification capabilities of both the time projection chambers and electromagnetic calorimeters of ND280. The measured ratio between the observed electron neutrino beam component and the prediction is $1.01\pm 0.10$ providing a direct confirmation of the neutrino fluxes and neutrino cross section modeling used for T2K neutrino oscillation analyses. Electron neutrinos coming from muons and kaons decay are also separately measured, resulting in a ratio with respect to the prediction of $0.68\pm 0.30$ and $1.10\pm 0.14$, respectively.

We report on a study of the dijet invariant-mass distribution in events with one identified lepton, a significant imbalance in the total event transverse momentum, and two jets. This distribution is sensitive to the possible production of a new particle in association with a $W$ boson, where the boson decays leptonically. We use the full data set of proton-antiproton collisions at 1.96 TeV center-of-mass energy collected by the Collider Detector at the Fermilab Tevatron, corresponding to an integrated luminosity of $8.9{\mathrm{fb}}^{-1}$. The data are found to be consistent with standard model expectations, and a 95% confidence level upper limit is set on the production cross section of a $W$ boson in association with a new particle decaying into two jets.

Recently it has been speculated that the Ward identities associated with the string dualities and the gauge symmetries can be used as guiding principles to find all components of the scattering amplitude of $n$ supergravitons from a given component of the S matrix. In this paper, we apply the Ward identities associated with the T duality and the gauge symmetries on the disk-level S-matrix element of one Ramond-Ramond (RR) $(p-3)$ form, one Neveu-Schwarz-Neveu-Schwarz (NSNS), and one Neveu-Schwarz (NS) state to find the corresponding S-matrix elements of the RR $(p-1)$ form, $(p+1)$ form, or the RR $(p+3)$ form on the world volume of a ${\mathrm{D}}_p$-brane. Moreover, we apply these Ward identities on the S-matrix element of one RR $(p-3)$ form and two NSNS states to find the corresponding S-matrix elements of the RR $(p-1)$ form, $(p+1)$ form, $(p+3)$ form, or the RR $(p+5)$ form.

We consider D7-branes probing several classes of Type IIB supergravity backgrounds, and study the classical problem of finding equilibrium configurations for the embedding functions. This is a method employed to model chiral symmetry breaking in the gravity dual of a strongly coupled, confining gauge theory. We unveil and discuss a new type of phase transition appearing in the gravity systems, which is similar in nature and meaning to bulk phase transitions on the lattice. The existence of this genre of phase transition puts a new, intrinsic limit on the region of parameter space which can be used to study the physics of the dual field theory. We complete the analysis of D7 embeddings in wrapped-D5 supergravity backgrounds, and explain in what cases chiral-symmetry breaking is sensibly modeled by the gravity construction.

Direct observations of neutron stars could tell us an imprint of modified gravity. However, it is generally difficult to resolve the degeneracy due to the uncertainties in the equation of state of neutron star matter and in gravitational theories. In this paper, we have successfully found the observational possibility to distinguish Eddington-inspired Born-Infeld gravity (EiBI) from general relativity. We show that the radii of neutron stars with $0.5M_{\odot }$ are strongly correlated with the neutron skin thickness of ${}^{208}\mathrm{Pb}$ independently of the equation of state, while this correlation depends on the coupling constant in EiBI. As a result, via the direct observations of the radius of the neutron star with $0.5M_{\odot }$ and the measurements of a neutron skin thickness of ${}^{208}\mathrm{Pb}$ by the terrestrial experiments, one could not only discriminate EiBI from general relativity but also estimate the coupling constant in EiBI.

A nice paper by Morrison [arXiv:1302.1860] demonstrates the recent convergence of opinion that has taken place concerning the graviton propagator on de Sitter background. We here discuss the few points which remain under dispute. First, the inevitable decay of tachyonic scalars really does result in their 2-point functions breaking de Sitter invariance. This is obscured by analytic continuation techniques which produce formal solutions to the propagator equation that are not propagators. Second, Morrison’s de Sitter invariant solution for the spin two sector of the graviton propagator involves derivatives of the scalar propagator at $M^2=0$, where it is not meromorphic unless de Sitter breaking is permitted. Third, de Sitter breaking does not require zero modes. Fourth, the ambiguity Morrison claims in the equation for the spin two structure function is fixed by requiring it to derive from a mode sum. Fifth, Morrison’s spin two sector is not “physically equivalent” to ours because their coincidence limits differ. Finally, it is only the noninvariant propagator that gets the time independence and scale invariance of the tensor power spectrum correctly.

We present a method to analyze black hole hair in the spherical symmetric sector of the Lovelock theory in arbitrary dimensions that is an alternative to solving the equations of motion in their complete form. We explicitly show that the method matches with the known black hole solutions for the vacuum and electro-vacuum spacetimes in Lovelock gravity theories. We further apply the method to the case of minimally coupled non-self-interacting massless scalar field and prove that there is no (non-self-interacting) massless scalar hair for the spherically symmetric Lovelock black holes.

We study the Schwinger pair production in confining theories. The production rate in an external electric field $E$ is numerically evaluated by using the holographic description. There exist two kinds of critical values of the electric field: (i) $E=E_{\mathrm{c}}$, above which there is no potential barrier and particles are freely generated, and (ii) $E=E_{\mathrm{s}}$, below which the confining string tension dominates the electric field and the pair production does not occur. We argue the universal exponents associated with the critical behaviors.

It has been suggested previously that an ultrasoft fermionic excitation develops, albeit with a small spectral weight, in a system of massless fermions and scalar bosons with Yukawa interaction at high temperature $T$. In this paper we study how this excitation is modified at finite chemical potential $\mu$. We relate the existence of the ultrasoft mode to symmetries, in particular charge conjugation, and a supersymmetry of the free system which is spontaneously broken by finite temperature and finite density effects, as argued earlier by Lebedev and Smilga. A nonvanishing chemical potential breaks both symmetries explicitly and maximally at zero temperature where the mode ceases to exist. A detailed calculation indicates that the ultrasoft excitation persists as long as $T\ge 0.71\mu$.

We study a simple extension of the Standard Model supplemented by an electroweak triplet scalar field to accommodate small neutrino masses by the type-II seesaw mechanism, while an additional singlet scalar field can play the role of cold dark matter (DM) in our Universe. This DM candidate is leptophilic for a wide range of model parameter space, and the lepton flux due to its annihilation carries information about the neutrino mass hierarchy. Using the recently released high-precision data on positron fraction and flux from the AMS-02 experiment, we examine the DM interpretation of the observed positron excess in our model for two kinematically distinct scenarios with the DM and triplet scalar masses (a) nondegenerate ($m_{\text{DM}}\gg m_{\mathrm{\Delta }}$) and (b) quasidegenerate ($m_{\text{DM}}\simeq m_{\mathrm{\Delta }}$). We find that a good fit to the AMS-02 data can be obtained in both cases (a) and (b) with a normal hierarchy of neutrino masses, while the inverted hierarchy case is somewhat disfavored. Although we require a larger boost factor for the normal hierarchy case, this is still consistent with the current upper limits derived from Fermi-LAT and IceCube data for case (a). Moreover, the absence of an excess antiproton flux as suggested by PAMELA data sets an indirect upper limit on the DM-nucleon spin-independent elastic scattering cross section, which is stronger than the existing DM direct detection bound from LUX in the AMS-02 preferred DM mass range.

Holographic AdS/QCD models of the Pomeron unite a string-based description of hadronic reactions of the pre-QCD era with the perturbative BFKL approach. The specific version we will use due to Stoffers and Zahed [1–5], is based on a semiclassical quantization of a “tube" (closed string exchange or open string virtual pair production) in its Euclidean formulation using the scalar Polyakov action. This model has a number of phenomenologically successful results. The periodicity of a coordinate around the tube allows the introduction of a Matsubara time and therefore an effective temperature $T_{\text{eff}}$ on the string. We observe that at the LHC energies and for sufficiently small impact parameter, $T_{\text{eff}}$ approaches and even exceeds the Hagedorn temperature of the QCD strings. Based on studies of the stringy thermodynamics of pure gauge theories we suggest that there should exist two new regimes of the Pomeron: the “near-critical” and the “postcritical” ones. In the former one, string excitations create a high-entropy “string ball,” with high energy and entropy but small pressure and free energy. If heavy enough, this ball becomes a (dual) black hole. As the intrinsic temperature of the string exceeds the Hagedorn temperature, the ball becomes a postcritical explosive “QGP ball.” The hydrodynamical explosion resulting from this scenario was predicted [6] to have radial flow exceeding any ever seen, even in heavy ion collisions, which was recently confirmed by CMS and ALICE at LHC. We also discuss the elastic scattering profile, finding some hints for new phases in it, as well as two-particle correlations.

We consider quantum chromodynamics (QCD) with $N_{\mathrm{c}}$ colors and $N_{\mathrm{f}}$ quark flavors at finite quark chemical potential ${\mu }_{\mathrm{q}}$ or isospin chemical potential ${\mu }_{\mathrm{I}}$. We specifically address the nature of the “silver blaze” behavior in the framework of $1/N_{\mathrm{c}}$ expansions. Starting with the QCD partition function, we implement Veneziano’s $N_{\mathrm{f}}/N_{\mathrm{c}}$ expansion to identify the density onset. We find the baryon mass $M_{\mathrm{B}}$ and the pion mass $m_{\pi }$ appearing from different orders of Veneziano’s expansion. We argue that the confining properties are responsible for the silver blaze behavior in the region of $m_{\pi }/2<{\mu }_{\mathrm{q}}<M_{\mathrm{B}}/N_{\mathrm{c}}$. We point out, however, that Veneziano’s expansion brings about a subtlety along the same line as the baryon problem in finite-density quenched lattice simulations. We emphasize that the large-$N_{\mathrm{c}}$ limit can allow for the physical ordering of $M_{\mathrm{B}}$ and $m_{\pi }$ thanks to the similarity between the large-$N_{\mathrm{c}}$ limit and the quenched approximation, while unphysical ghost quarks contaminate the baryon sector if $N_{\mathrm{c}}$ is finite. We also discuss the “orientifold” large-$N_{\mathrm{c}}$ limit that does not quench quark loops.

We examine the response of an Unruh-DeWitt particle detector coupled to a massless scalar field on the ($3+1$)-dimensional Schwarzschild spacetime, in the Boulware, Hartle-Hawking and Unruh states, for static detectors and detectors on circular geodesics, by primarily numerical methods. For the static detector, the response in the Hartle-Hawking state exhibits the known thermality at the local Hawking temperature, and the response in the Unruh state is thermal at the local Hawking temperature in the limit of a large detector energy gap. For the circular-geodesic detector, we find evidence of thermality in the limit of a large energy gap for the Hartle-Hawking and Unruh states, at a temperature that exceeds the Doppler-shifted local Hawing temperature. Detailed quantitative comparisons between the three states are given. The response in the Hartle-Hawking state is compared with the response in the Minkowski vacuum and in the Minkowski thermal state for the corresponding Rindler, drifted Rindler, and circularly accelerated trajectories. The analysis takes place within first-order perturbation theory and relies in an essential way on stationarity.

Kilohertz quasi periodic oscillations (QPOs) can be used as a probe of the inner regions of accretion disks in compact stars and hence also of the properties of the central object. Most models of kHz QPOs involve epicyclic frequencies to explain their origin. We compute the epicyclic frequencies of nearly circular orbits around rotating strange quark stars. The MIT bag model is used to model the equation of state of quark matter, and the uniformly rotating stellar configurations are computed in full general relativity. The vertical epicyclic frequency and the related nodal precession rate of inclined orbits are very sensitive to the oblateness of the rotating star. For rotating stellar models of moderate and high-mass strange stars, the sense of the nodal precession changes at a certain rotation rate. At lower stellar rotation rates, the orbital nodal precession is prograde, as it is in the Kerr metric, while at higher rotation rates, the precession is retrograde, as it is for Maclaurin spheroids. Thus, qualitatively, the orbits around rapidly rotating strange quark stars are affected more strongly by the effects of stellar oblateness than by the effects of general relativity. We show that epicyclic and orbital frequencies calculated numerically for small mass strange stars are in very good agreement with analytical formulas for Maclaurin spheroids.

The steady-state propagation of a phase-transition front is classified, according to hydrodynamics, as a deflagration or a detonation, depending on its velocity with respect to the fluid. These propagation modes are further divided into three types, namely, weak, Jouguet, and strong solutions, according to their disturbance of the fluid. However, some of these hydrodynamic modes will not be realized in a phase transition. One particular cause is the presence of instabilities. In this work we study the linear stability of weak detonations, which are generally believed to be stable. After discussing in detail the weak detonation solution, we consider small perturbations of the interface and the fluid configuration. When the balance between the driving and friction forces is taken into account, it turns out that there are actually two different kinds of weak detonations, which behave very differently as functions of the parameters. We show that the branch of stronger weak detonations are unstable, except very close to the Jouguet point, where our approach breaks down.

The most stringent bounds on the absolute neutrino mass scale come from cosmological data. These bounds are made possible because massive relic neutrinos affect the expansion history of the universe and lead to a suppression of matter clustering on scales smaller than the associated free streaming length. However, the resulting effect on cosmological perturbations is relative to the primordial power spectrum of density perturbations from inflation, so freedom in the primordial power spectrum affects neutrino mass constraints. Using measurements of the cosmic microwave background (CMB), the galaxy power spectrum and the Hubble constant, we constrain neutrino mass and number of species for a model-independent primordial power spectrum. Describing the primordial power spectrum by a 20-node spline, we find that the neutrino mass upper limit is a factor 3 weaker than when a power law form is imposed, if only CMB data are used. The primordial power spectrum itself is constrained to better than 10% in the wave vector range $k\approx 0.01-0.25{\mathrm{Mpc}}^{-1}$. Galaxy clustering data and a determination of the Hubble constant play a key role in reining in the effects of inflationary freedom on neutrino constraints. The inclusion of both eliminates the inflationary freedom degradation of the neutrino mass bound, giving for the sum of neutrino masses $\mathrm{\Sigma }{m}_{\nu }<0.18\mathrm{eV}$ (at 95% confidence level, $\text{Planck}+\text{BOSS}+H_0$), approximately independent of the assumed primordial power spectrum model. When allowing for a free effective number of species, $N_{\text{eff}}$, the joint constraints on $\mathrm{\Sigma }{m}_{\nu }$ and $N_{\text{eff}}$ are loosened by a factor 1.7 when the power law form of the primordial power spectrum is abandoned in favor of the spline parametrization.

We investigate the consistency of a scenario in which the baryon asymmetry, dark matter, and the cosmic density perturbation are generated simultaneously through the evaporation of primordial black holes (PBHs). This scenario can explain the coincidence of the dark matter and baryon densities of the Universe, and is free from the isocurvature perturbation problem. We show that this scenario predicts the masses of PBHs, right-handed neutrinos and dark matter, the Hubble scale during inflation and the non-Gaussianity. We also discuss the testability of the scenario by detecting high-frequency gravitational waves from PBHs.

In this paper we show that the Universe is already strongly magnetized at very early epochs during cosmic evolution. Our calculations are based on the efficient amplification of weak magnetic seed fields, which are unavoidably present in the early Universe, by the turbulent small-scale dynamo. We identify two mechanisms for the generation of turbulence in the radiation dominated epoch where velocity fluctuations are produced by the primordial density perturbation and by possible first-order phase transitions at the electroweak or QCD scales. We show that all the necessities for the small-scale dynamo to work are fulfilled. Hence, this mechanism, operating due to primordial density perturbations, guarantees fields with comoving field strength $B_0\sim {10}^{-6}{ϵ}^{1/2}\mathrm{nG}$ on scales up to ${\lambda }_c\sim 0.1\mathrm{pc}$, where $ϵ$ is the saturation efficiency. The amplification of magnetic seed fields could be even larger if there are first-order phase transitions in the early Universe. Where, on scales up to ${\lambda }_c\sim 100\mathrm{pc}$, the comoving field strength due to this mechanism will be $B_0\sim {10}^{-3}{ϵ}^{1/2}\mathrm{nG}$ at the present time. Such fields, albeit on small scales, can play an important role in structure formation and could provide an explanation to the apparently observed magnetic fields in the voids of the large-scale structure.

We report on the search for neutrino-induced particle showers, so-called cascades, in the IceCube-40 detector. The data for this search were collected between April 2008 and May 2009 when the first 40 IceCube strings were deployed and operational. Three complementary searches were performed, each optimized for different energy regimes. The analysis with the lowest energy threshold (2 TeV) targeted atmospheric neutrinos. A total of 67 events were found, consistent with the expectation of 41 atmospheric muons and 30 atmospheric neutrino events. The two other analyses targeted a harder, astrophysical neutrino flux. The analysis with an intermediate threshold of 25 TeV leads to the observation of 14 cascadelike events, again consistent with the prediction of 3.0 atmospheric neutrino and 7.7 atmospheric muon events. We hence set an upper limit of ${\mathrm{E}}^2{\mathrm{\Phi }}_{\lim }\le 7.46\times {10}^{-8}\mathrm{GeV}{\mathrm{sr}}^{-1}{\mathrm{s}}^{-1}{\mathrm{cm}}^{-2}$ (90% C.L.) on the diffuse flux from astrophysical neutrinos of all neutrino flavors, applicable to the energy range 25 TeV to 5 PeV, assuming an $E_{\nu }^{-2}$ spectrum and a neutrino flavor ratio of $1:1:1$ at the Earth. The third analysis utilized a larger and optimized sample of atmospheric muon background simulation, leading to a higher energy threshold of 100 TeV. Three events were found over a background prediction of 0.04 atmospheric muon events and 0.21 events from the flux of conventional and prompt atmospheric neutrinos. Including systematic errors this corresponds to a $2.7\sigma$ excess with respect to the background-only hypothesis. Our observation of neutrino event candidates above 100 TeV complements IceCube’s recently observed evidence for high-energy astrophysical neutrinos.