We study the phase diagram of black D3 geometry with uniformly distributed D-instanton charge using the probe D7 brane. In the presence of uniform D-instanton charges, quarks can be confined, although gluons are not, because baryon vertices are allowed due to the net repulsive force on the on the probe D-branes. Since there is no scale in the geometry itself apart from the horizon size, there is no Hawking-Page transition. As a consequence, the D7 brane embedding can encode the effect of the finite temperature as well as finite baryon density even for low temperature. The probe D-brane embedding, however, undergoes a phase transition which can be interpreted as a chiral transition as we change temperature and density. We studied such phase transitions and calculated the constituent quark mass, chiral condensation, and the binding energy of baryons as function of the density. The baryon vertex melting is identified as the quark deconfinement. We draw the phase diagram according to these transitions.

We propose a new method for investigating the global properties of the retarded Green’s function $G_R(x^{\prime },x)$ for fields propagating on an arbitrary globally hyperbolic spacetime. Our method combines the Hadamard form for $G_R$ (this form is only valid within a normal neighborhood of $x$) together with Kirchhoff’s integral representation for the field in order to calculate $G_R$ outside the maximal normal neighborhood of $x$. As an example, we apply this method to the case of a scalar field on a black hole toy-model spacetime, the Plebański-Hacyan spacetime, ${\mathbb{M}}_2\times {\mathbb{S}}^2$. The method allows us to determine in an exact manner that the singularity structure of the “direct” term in the Hadamard form for $G_R(x^{\prime },x)$ changes from a form $\delta (\sigma )$ to “$1/\pi \sigma$” after the null geodesic joining $x$ and $x^{\prime }$ has crossed a caustic point, where $\sigma$ is the world function. Furthermore, there is a change of form from a Heaviside step function $H(-\sigma )$ to a “$-\ln |\sigma |/\pi$” in the “tail” term, which has not been explicitly noted before in the literature. We complement the results from the Kirchhoff integral method with an analysis for large-$\ell$ of the Green’s function modes. This analysis allows us to determine the singularity structure after null geodesics have crossed an arbitrary number of caustics, although it raises a causality issue which the Kirchhoff integral method resolves. Because of the similarity in the caustic structure of the spacetimes, we expect our main results for wave propagation to be valid also on Schwarzschild spacetime.

The no-hair conjecture statement is enhanced to include static regular and singular black-hole solutions, based on the class of nonlinear electrodynamics proposed by Plebański coupled to Einstein theory. In particular, we focus, as example, on regular black-hole solutions, i.e., black holes where the space-time metric everywhere is nonsingular, in the framework of General Relativity theory. Time-reversal invariance implies the existence of two separate non-overlapping cases: a purely gravito-electric case, and a purely gravito-magnetic one. We prove the enhanced no-hair conjecture for both cases. Moreover, the generalization of the conjecture including also the couplings to non-Abelian matter is also discussed.

We study the effect of a very strong homogeneous magnetic field $B$ on the thermal deconfinement transition within the simplest phenomenological approach: the MIT bag pressure for the quark-gluon plasma and a gas of pions for the hadronic sector. Even though the model is known to be crude in numerical precision and misses the correct nature of the (crossover) transition, it provides a simple setup for the discussion of some subtleties of vacuum and thermal contributions in each phase, and should provide a reasonable qualitative description of the critical temperature in the presence of $B$. We find that the critical temperature decreases, saturating for very large fields.

The LHC inverse problem refers to the difficulties in determining the parameters of an underlying theory from data (to be) taken by the LHC experiments: if they find signals of new physics, and an underlying theory is assumed, could its parameters be determined uniquely, or do different parameter choices give indistinguishable experimental signatures? This inverse problem was studied before for a supersymmetric standard model with 15 free parameters. This earlier study found 283 indistinguishable pairs of parameter choices, called degenerate pairs, even if backgrounds are ignored. We can resolve all but 23 of those pairs by constructing a true ${\chi }^2$ distribution using mostly counting observables. The elimination of systematic errors would even allow separating the residual degeneracies. Taking the standard model background into account we still can resolve 237 of the 283 “degenerate” pairs. This indicates that (some of) our observables should also be useful for the purpose of determining the values of supersymmetric parameters.

The relation between the baryon number in QCD at nonzero chemical potential and the spectral density of the baryon number Dirac operator, ${\gamma }_0(D+m)$, is examined. We show that extreme oscillations of the spectral density, caused by the QCD sign problem, are essential for the formation of the average baryon number when $\mu >m_{\pi }/2$. We compute the oscillating region of the spectral density using chiral perturbation theory. The extreme oscillations have a microscopic period and are resolved using random matrix theory.

We study hadron correlators upon artificial restoration of the spontaneously broken chiral symmetry. In a dynamical lattice simulation we remove the lowest lying eigenmodes of the Dirac operator from the valence quark propagators and study the evolution of the hadron masses obtained. All mesons and baryons in our study, except for a pion, survive the unbreaking of the chiral symmetry and their exponential decay signals become essentially better. From the analysis of the observed spectroscopic patterns we conclude that confinement still persists while the chiral symmetry is restored. All hadrons fall into different chiral multiplets. The broken $U(1{)}_A$ symmetry does not get restored upon unbreaking the chiral symmetry. We also observe signals of some higher symmetry that includes chiral symmetry as a subgroup. Finally, from comparison of the $\Delta -N$ splitting before and after the unbreaking of the chiral symmetry, we conclude that both the color-magnetic and the flavor-spin quark-quark interactions are of equal importance.

We show that the tracking system in a collider detector can be used to efficiently identify boosted massive particles from their QCD backgrounds. We examine variables defined with tracking information which are sensitive to jet radiation patterns, including charged particle multiplicity and $N$-subjettiness. These variables are barely correlated with variables sensitive to the hard splitting scale in the jet, such as the filtered jet mass. Therefore these two kinds of variables should be combined to optimize the discriminating power. We illustrate the method with $W$ jet tagging. It is shown that for jet $p_T=500\mathrm{GeV}$, one can gain a factor of 1.6 in statistical significance by combining filtered jet mass and charged particle multiplicity, over filtered mass alone. Adding $N$-subjettiness increases the factor to 1.8.

In effective field theories it is common to identify the onset of new physics with the violation of tree-level unitarity. However, we show that this is parametrically incorrect in the case of chiral perturbation theory, and is probably theoretically incorrect in general. In the chiral theory, we explore perturbative unitarity violation as a function of the number of colors and the number of flavors, holding the scale of the “new physics” (i.e. QCD) fixed. This demonstrates that the onset of new physics is parametrically uncorrelated with tree-unitarity violation. When the latter scale is lower than that of new physics, the effective theory must heal its unitarity violation itself, which is expected because the field theory satisfies the requirements of unitarity. In the chiral theory, the self-healing results in a resonant structure with scalar quantum numbers. In the electroweak variant of this argument, the structure must have the properties of the Higgs and must couple proportional to the mass in both gauge boson and fermion scattering. A similar example can be seen in the case of general relativity coupled to multiple matter fields, where iteration of the vacuum polarization diagram restores unitarity. We present arguments that suggest the correct identification should be connected to the onset of inelasticity rather than unitarity violation. We describe how the onset of inelasticity can occur in the effective theory, although it does not appear possible to predict the onset reliably.

We study nonstandard top quark couplings in the effective field theory approach. All nine dimension-six operators that generate anomalous couplings between the electroweak gauge bosons and the third-generation quarks are included. We calculate their contributions at tree level and one loop to all major precision electroweak observables. The calculations are compared with data to obtain constraints on eight of these operators.

The recent results of the ATLAS and CMS experiments indicate $116\mathrm{GeV}\lesssim M_H\lesssim 131\mathrm{GeV}$ and $115\mathrm{GeV}\lesssim M_H\lesssim 127\mathrm{GeV}$, respectively, for the mass of the Higgs boson in the standard model (SM) at the 95% confidence level. In particular, both experiments point to a preferred narrow mass range $M_H\simeq (124\cdots 126)\mathrm{GeV}$. We examine the impact of this preliminary result of $M_H$ on the SM vacuum stability by using the two-loop renormalization-group equations, and arrive at the cutoff scale ${\Lambda }_{\mathrm{VS}}\sim 4\times {10}^{12}\mathrm{GeV}$ (for $M_H=125\mathrm{GeV}$, $M_t=172.9\mathrm{GeV}$, and ${\alpha }_s(M_Z)=0.1184$), where the absolute stability of the SM vacuum is lost and some kind of new physics might take effect. We update the values of running lepton and quark masses at some typical energy scales, including the ones characterized by $M_H$, 1 TeV and ${\Lambda }_{\mathrm{VS}}$, with the help of the two-loop renormalization-group equations. The branching ratios of some important two-body Higgs decay modes, such as $H\to b\overline{b}$, $H\to {\tau }^{+}{\tau }^{-}$, $H\to \gamma \gamma$, $H\to W^{+}{W}^{-}$, and $H\to ZZ$, are also recalculated by inputting the values of relevant particle masses at $M_H$.

We consider static cosmological solutions along with their stability properties in the framework of a recently proposed theory of massive gravity. We show that the modification introduced in the cosmological equations leads to several new solutions, only sourced by a perfect fluid, generalizing the Einstein static universe found in general relativity. Using dynamical system techniques and numerical analysis, we show that the found solutions can be either neutrally stable or unstable against spatially homogeneous and isotropic perturbations.

Inclusive jet and dijet cross sections have been measured in proton-proton collisions at a center-of-mass energy of 7 TeV using the ATLAS detector at the Large Hadron Collider. The cross sections were measured using jets clustered with the anti-$k_t$ algorithm with parameters $R=0.4$ and $R=0.6$. These measurements are based on the 2010 data sample, consisting of a total integrated luminosity of $37{\mathrm{pb}}^{-1}$. Inclusive jet double-differential cross sections are presented as a function of jet transverse momentum, in bins of jet rapidity. Dijet double-differential cross sections are studied as a function of the dijet invariant mass, in bins of half the rapidity separation of the two leading jets. The measurements are performed in the jet rapidity range $|y|<4.4$, covering jet transverse momenta from 20 GeV to 1.5 TeV and dijet invariant masses from 70 GeV to 5 TeV. The data are compared to expectations based on next-to-leading-order QCD calculations corrected for nonperturbative effects, as well as to next-to-leading-order Monte Carlo predictions. In addition to a test of the theory in a new kinematic regime, the data also provide sensitivity to parton distribution functions in a region where they are currently not well-constrained.

Soft and collinear factorizations can be used to construct expressions for amplitudes in theories of gravity. We generalise the “half-soft” functions used previously to “soft-lifting” functions and use these to generate tree and one-loop amplitudes. In particular we construct expressions for maximally helicity-violating tree amplitudes and the rational terms in one-loop amplitudes in the specific context of $\mathcal{N}=4$ supergravity. To completely determine the rational terms collinear factorization must also be used. The rational terms for $\mathcal{N}=4$ have a remarkable diagrammatic interpretation as arising from algebraic link diagrams.

Inspired by the model of Jarvinen and Kiritsis, we present a simple holographic model for the onset of chiral symmetry breaking at the edge of the conformal window in QCD in the Veneziano limit. Our most naive model enforces the QCD two-loop running coupling on a D3/D7 holographic brane system. The mass of the holographic field, describing the chiral condensate in the model, is driven below the Breitenlohner-Freedman bound when the running is sufficiently strong, triggering chiral symmetry breaking for $N_f/N_c<2.9$. This model though contains too great a remnant of supersymmetry and does not correctly encode the perturbative anomalous dimensions of QCD. In a second model we impose the QCD anomalous dimension result and find chiral symmetry breaking sets in for $N_f/N_c=4$ at a Berezinsky-Kosterlitz-Thouless–type phase transition. In this case the transition is triggered when the anomalous dimension of the mass operator ${\gamma }_m=1$.

Building on our previous work [Phys. Rev. D 82, 085016 (2010)], we show in this paper how a Brownian motion on a short scale can originate a relativistic motion on scales that are larger than particle’s Compton wavelength. This can be described in terms of polycrystalline vacuum. Viewed in this way, special relativity is not a primitive concept, but rather it statistically emerges when a coarse-graining average over distances of order, or longer than the Compton wavelength is taken. By analyzing the robustness of such a special relativity under small variations in the polycrystalline grain-size distribution we naturally arrive at the notion of doubly-special relativistic dynamics. In this way, a previously unsuspected, common statistical origin of the two frameworks is brought to light. Salient issues such as the rôle of gauge fixing in emergent relativity, generalized commutation relations, Hausdorff dimensions of representative path-integral trajectories and a connection with Feynman chessboard model are also discussed.

The convexity of a scalar effective potential is a well-known property, and, in the situation of spontaneous symmetry breaking, leads to the so-called Maxwell construction, characterized by a flat effective potential between the minima of the bare potential. Simple derivations are given here, which show how linear effective potentials arise from nontrivial saddles points which dominate the partition function, for a self-interacting scalar field and for a Yukawa model.

We study the mass spectrum of the quark sector in a special type-I-like model with gauge symmetry $SU(3{)}_c\otimes SU(3{)}_L\otimes U(1{)}_X$. By considering couplings with scalar triplets at large ($\sim \mathrm{TeV}$) and small ($\sim \mathrm{GeV}$) scales, we obtain specific zero-texture mass matrices for the quarks which predict three massless quarks ($u$, $d$, $s$) and three massive quarks ($c$, $b$, $t$) at the electroweak scale ($\sim \mathrm{GeV}$). Taking into account mixing couplings with three heavy quarks at large scales predicted by the model, the three massless quarks obtain masses at small order that depend on the inverse of the large scale. Thus, masses of the form $m_u\lesssim m_d<m_s\sim \mathrm{MeV}$ and $m_{c,b,t}\sim \mathrm{GeV}$ can be obtained naturally from the gauge structure of the model.

We analyze the entanglement tradeoff between particle and antiparticle modes of a charged bosonic field between inertial and uniformly accelerated observers. In contrast with previous results for fermionic fields, we find that the entanglement redistribution between particle and antiparticle modes does not prevent the entanglement from vanishing in the infinite acceleration limit.

We study the sigma model with $SU(N)\times SU(N)$ symmetry in $1+1$ dimensions. The two- and four-particle form factors of the Noether current operators are found, by combining the integrable-bootstrap method with the large-$N$ expansion.