We study baryonic matter in holographic QCD with $\mathrm{D}4/\mathrm{D}8/\overline{\mathrm{D}8}$ multi-D brane system in type IIA superstring theory. The baryon is described as the “brane-induced Skyrmion,” which is a topologically nontrivial chiral soliton in the four-dimensional meson effective action induced by holographic QCD. We employ the “truncated-resonance model” approach for the baryon analysis, including pion and $\rho$ meson fields below the ultraviolet cutoff scale $M_{\mathrm{KK}}\sim 1\mathrm{GeV}$, to keep the holographic duality with QCD. We describe the baryonic matter in large $N_c$ as single brane-induced Skyrmion on the three-dimensional closed manifold $S^3$ with finite radius $R$. The interactions between baryons are simulated by the curvature of the closed manifold $S^3$, and the decrease of the size of $S^3$ represents the increase of the total baryon-number density in the medium in this modeling. We investigate the energy density, the field configuration, the mass and the root-mean-square radius of single baryon on $S^3$ as the function of its radius $R$. We find a new picture of “pion dominance” near the critical density in the baryonic matter, where all the (axial) vector meson fields disappear and only the pion fields survive. We also find the swelling phenomena of the baryons as the precursor of the deconfinement, and propose the mechanism of the swelling in the general context of QCD. The properties of the deconfinement and the chiral symmetry restoration in the baryonic matter are examined by taking the proper order parameters. We also compare our truncated-resonance model with another instanton description of the baryon in holographic QCD, considering the role of cutoff scale $M_{\mathrm{KK}}$.

The recent introduction of a deformed nonminimal version of the noncommutative standard model in the enveloping-algebra approach, having a one-loop renormalizable gauge sector involving a higher order gauge term, motivates us to consider the possibility of extending the fermion sector with additional deformations, i.e. higher order fermionic terms. Since the renormalizability properties of the fermion sector of the model are not yet fully known, we work with an effective fermion Lagrangian, which includes noncommutative higher order terms involving a contraction with the noncommutative $\theta$ tensor aside from the star products, so that these terms annihilate in the commutative limit. Some of these terms violate CPT in the weak sector, and some violate $CP$ in the strong and hypercharge sectors. We apply this framework to the re-evaluation of the decay rates of quarkonia ($\overline{q}{q}_1=J/\psi$, ${\rm Y}$) into two photons. These decays, which are forbidden in the ordinary standard model, had been previously studied as possible signals for noncommutativity, but not in the framework of the better behaved deformed nonminimal version of the noncommutative standard model. Weak CPT or strong-hypercharge $CP$ violating interactions do not contribute to the result. If the parameters of the model take natural values, for the vast majority of configurations the resulting branching ratios are enhanced with respect to their values in the minimal version of the noncommutative standard model. Also for more than half of the parameter space, the rates are larger than the maximal rates that were calculated in the undeformed version of the nonminimal noncommutative standard model. Tuning the dimensionless parameters the predicted branching ratios can fall within the current experimental bounds.

This paper explores the properties of the Pauli-Lubanski spin vector for the general motion of spin-$1/2$ particles in curved space-time. Building upon previously determined results in flat space-time, it is shown that the associated Casimir scalar for spin possesses both gravitational contributions and frame-dependent contributions due to noninertial motion, where the latter represents a possible quantum violation of Lorentz invariance that becomes significant at the Compton wavelength scale. When applied to muon decay near the event horizon of a microscopic Kerr black hole, it is shown that its differential cross section is strongly affected by curvature, with particular sensitivity to changes in the black hole’s spin angular momentum. In the absence of curvature, the noninertial contributions to the decay spectrum are also identified and explored in detail, where its potential for observation is highest for large electron opening angles. It is further shown how possible contributions to noncommutative geometry can emerge from within this formalism at some undetermined length scale. Surprisingly, while the potential exists to identify noncommutative effects in muon decay, the relevant terms make no contribution to the decay spectrum, for reasons which remain unknown.

We consider a multidimensional cosmological model with nonlinear quadratic $R^2$ and quartic $R^4$ actions. As a matter source, we include a monopole form field, a D-dimensional bare cosmological constant and the tensions of branes located at fixed points. In the spirit of the universal extra dimension model, the standard model fields are not localized on branes, but rather they can move in the bulk. We define conditions that ensure stable compactification of the internal space in zero minima of the effective potentials. Such effective potentials may have a rather complicated form with a number of local minima, maxima, and saddle points. We investigate inflation in such models. It is shown that the $R^2$- and $R^4$ models can produce up to 10 and 22 e-foldings, respectively. These values are not sufficient to solve the homogeneity and isotropy problem, but they are large enough to explain recent cosmic microwave background data. Additionally, the $R^4$ model can provide conditions for eternal topological inflation. The main drawback of the obtained inflationary models consists in a spectral index $n_s$ that is less than the presently observed $n_s\approx 1$. For the $R^4$ model we find, e.g., $n_s\approx 0.61$.

We propose a comprehensive theory of dark matter that explains the recent proliferation of unexpected observations in high-energy astrophysics. Cosmic ray spectra from ATIC and PAMELA require a WIMP (weakly interacting massive particle). with mass $M_{\chi }\sim 500–800\mathrm{GeV}$ that annihilates into leptons at a level well above that expected from a thermal relic. Signals from WMAP and EGRET reinforce this interpretation. Limits on $\overline{p}$ and ${\pi }^0\mathrm{\text{−}}\gamma$’s constrain the hadronic channels allowed for dark matter. Taken together, we argue these facts imply the presence of a new force in the dark sector, with a Compton wavelength $m_{\varphi }^{-1}\gtrsim 1{\mathrm{GeV}}^{-1}$. The long range allows a Sommerfeld enhancement to boost the annihilation cross section as required, without altering the weak-scale annihilation cross section during dark matter freeze-out in the early universe. If the dark matter annihilates into the new force carrier $\varphi$, its low mass can make hadronic modes kinematically inaccessible, forcing decays dominantly into leptons. If the force carrier is a non-Abelian gauge boson, the dark matter is part of a multiplet of states, and splittings between these states are naturally generated with size $\alpha m_{\varphi }\sim \mathrm{MeV}$, leading to the eXciting dark matter (XDM) scenario previously proposed to explain the positron annihilation in the galactic center observed by the INTEGRAL satellite; the light boson invoked by XDM to mediate a large inelastic scattering cross section is identified with the $\varphi$ here. Somewhat smaller splittings would also be expected, providing a natural source for the parameters of the inelastic dark matter (iDM) explanation for the DAMA annual modulation signal. Since the Sommerfeld enhancement is most significant at low velocities, early dark matter halos at redshift $\sim 10$ potentially produce observable effects on the ionization history of the universe. Because of the enhanced cross section, detection of substructure is more probable than with a conventional WIMP. Moreover, the low velocity dispersion of dwarf galaxies and Milky Way subhalos can increase the substructure annihilation signal by an additional order of magnitude or more.

A search for the lepton flavor violating decays ${\tau }^{-}\to l^{-}{K}_S^0$ ($l=e$ or $\mu$) has been performed using a data sample corresponding to an integrated luminosity of $469{\mathrm{fb}}^{-1}$, collected with the BABAR detector at the SLAC PEP-II $e^{+}{e}^{-}$ asymmetric energy collider. No statistically significant signal has been observed in either channel and the estimated upper limits on branching fractions are $\mathcal{B}({\tau }^{-}\to e^{-}{K}_S^0)<3.3\times {10}^{-8}$ and $\mathcal{B}({\tau }^{-}\to {\mu }^{-}{K}_S^0)<4.0\times {10}^{-8}$ at 90% confidence level.

We present an alternative geometric inspired derivation of the quantum cosmology arising from a brane universe in the context of geodetic gravity. We set up the Regge-Teitelboim model to describe our universe, and we recover its original dynamics by thinking of such field theory as a second-order derivative theory. We refer to an Ostrogradski Hamiltonian formalism to prepare the system to its quantization. Our analysis highlights the second-order derivative nature of the RT model and the inherited geometrical aspect of the theory. A canonical transformation brings us to the internal physical geometry of the theory and induces its quantization straightforwardly. By using the Dirac canonical quantization method our approach comprises the management of both first- and second-class constraints where the counting of degrees of freedom follows accordingly. At the quantum level our Wheeler-De Witt equation agrees with previous results recently found. On these lines, we also comment upon the compatibility of our approach with the Hamiltonian approach proposed by Davidson and coworkers.

Weak lensing (WL) distortions of distant galaxy images are sensitive to neutrino masses by probing the suppression effect on clustering strengths of total matter in large-scale structure. We use the latest measurements of WL correlations, the Canada-France-Hawaii Telescope Legacy Survey data, to explore constraints on neutrino masses. We find that, while the WL data alone cannot place a stringent limit on neutrino masses due to parameter degeneracies, the constraint can be significantly improved when combined with other cosmological probes, such as the WMAP 5-year data (WMAP5) and the distance measurements of type-Ia supernovae (SNe) and baryon acoustic oscillations (BAO). The upper bounds on the sum of neutrino masses are $\sum _{}^{}{m}_{\nu }=1.1$, 0.76, and 0.54 eV (95% CL) for $\mathrm{WL}+\mathrm{WMAP}5$, $\mathrm{WMAP}5+\mathrm{SNe}+\mathrm{BAO}$, and $\mathrm{WL}+\mathrm{WMAP}5+\mathrm{SNe}+\mathrm{BAO}$, respectively, assuming a flat $\Lambda \mathrm{CDM}$ model with finite-mass neutrinos. In deriving these constraints, our analysis includes the non-Gaussian covariances of the WL correlation functions to properly take into account significant correlations between different angles.

Consistency relations between growth of structure and expansion history observables exist for any physical explanation of cosmic acceleration, be it a cosmological constant, scalar field quintessence, or a general component of dark energy that is smooth relative to dark matter on small scales. The high-quality supernova sample anticipated from an experiment like the SuperNova/Acceleration Probe and cosmic microwave background data expected from Planck thus make strong predictions for growth and expansion observables that additional observations can test and potentially falsify. We perform a Markov chain Monte Carlo likelihood exploration of the strength of these consistency relations based on a complete parametrization of dark energy behavior by principal components. For $\Lambda \mathrm{CDM}$, future supernova and cosmic microwave background data make percent level predictions for growth and expansion observables. For quintessence, many of the predictions are still at a level of a few percent with most of the additional freedom coming from curvature and early dark energy. While such freedom is limited for quintessence where phantom equations of state are forbidden, it is larger in the smooth dark energy class. Nevertheless, even in this general class predictions relating growth measurements at different redshifts remain robust, although predictions for the instantaneous growth rate do not. Finally, if observations falsify the whole smooth dark energy class, new paradigms for cosmic acceleration such as modified gravity or interacting dark matter and dark energy would be required.

Recently it was noticed that among many scenarios of new physics leptoquarks might compensate for the disagreement between the lattice and experimental results for the charmed strange meson decay constant. The leptoquarks might modify also the flavor changing neutral current charm decays. In this study we investigate the impact of the scalar leptoquark with electric charge $-1/3$ on the dilepton invariant mass distribution in the $D^{+}\to {\pi }^{+}{\mu }^{+}{\mu }^{-}$ decay and on the branching ratios of the $D^0\to {\mu }^{+}{\mu }^{-}$ using the existing experimental results.

We discuss the vacuum structure of QCD with two flavors of Wilson fermions. We derive two possible scenarios: (i) If the spectral density ${\rho }_U(\lambda ,\kappa )$ of the overlap Hamiltonian in a fixed background gauge field is not symmetric in $\lambda$, Hermiticity is violated and Hermiticity violation effects could influence numerical determinations of the $\eta$ meson mass if we are not near enough to the continuum limit, where Hermiticity should be recovered; (ii) otherwise we argue that, under certain assumptions, new phases appear beside the Aoki phase, which can be characterized by a nonvanishing vacuum expectation value of $i{\overline{\psi }}_u{\gamma }_5{\psi }_u+i{\overline{\psi }}_d{\gamma }_5{\psi }_d$, and with vacuum states that cannot be connected with the Aoki vacua by parity-flavor symmetry transformations. Quenched numerical simulations suggest that the second scenario is more likely realized.

$CP$ violation is a major challenge of contemporary particle physics. It has been discovered in kaon decays and appears also in $B$ decays, where the $B^0\to J/\psi K_{\mathrm{S},\mathrm{L}}$ channels are considered to be clean probes of this phenomenon. Recent $B$-factory data challenge the description of $CP$ violation in the standard model of particle physics, showing some “tension” with theoretical predictions. We take a detailed look at certain standard-model contributions, which are usually neglected, and point out that they can be included unambiguously through measurements of the $B^0\to J/\psi {\pi }^0$ observables. Using the most recent data, we show that the tension with the standard model is softened, and we constrain a possible new-physics phase in $B^0-{\overline{B}}^0$ mixing. Our strategy is crucial to fully exploit the accuracy of the search for this kind of new physics at the LHC and future super-flavor factories.

Torsion models constitute a well-known class of extended quantum gravity models. In this paper we study some phenomenological consequences of a torsion field interacting with fermions at LHC. A torsion field could appear as a new heavy state characterized by its mass and couplings to fermions. These new states will form a resonance decaying into difermions, as occurs in many extensions of the standard model, such as models predicting the existence of additional neutral gauge bosons, usually named $Z^{\prime }$. Using the dielectron channel we evaluate the integrated luminosity needed for a $5\sigma$ discovery as a function of the torsion mass, for different coupling values. We also calculate the luminosity needed to discriminate, with 95% C.L., the two possible different torsion natures. Finally, we show that the observed signal coming from the torsion field could be distinguished from a signal coming from a new neutral gauge boson, provided there is enough luminosity.

We report on a two-loop supersymmetric contribution to the magnetic moment $(g-2{)}_{\mu }$ of the muon which is enhanced by two powers of $\tan \beta$. This contribution arises from a shift in the relation between the muon mass and Yukawa coupling and can increase the supersymmetric contribution to $(g-2{)}_{\mu }$ sizably. As a result, if the currently observed $3\sigma$ deviation between the experimental and SM theory value of $(g-2{)}_{\mu }$ is analyzed within the minimal supersymmetric standard model (MSSM), the derived constraints on the parameter space are modified significantly: If $(g-2{)}_{\mu }$ is used to determine $\tan \beta$ as a function of the other MSSM parameters, our corrections decrease $\tan \beta$ by roughly 10% for $\tan \beta =50$.

We address the problem of the apparently very small magnitude of $CP$ violation in the standard model, measured by the Jarlskog invariant $J$. In order to make statements about probabilities for certain values of $J$, we seek to find a natural measure on the space of Kobayashi-Maskawa matrices, the double quotient $U(1{)}^2\setminus SU(3)/U(1{)}^2$. We review several possible, geometrically motivated choices of the measure, and compute expectation values for powers of $J$ for these measures. We find that different choices of the measure generically make the observed magnitude of $CP$ violation appear finely tuned. Since the quark masses and the mixing angles are determined by the same set of Yukawa couplings, we then do a second calculation in which we take the known quark mass hierarchy into account. We construct the simplest measure on the space of $3\times 3$ Hermitian matrices which reproduces this known hierarchy. Calculating expectation values for powers of $J$ in this second approach, we find that values of $J$ close to the observed value are now rather likely, and there does not seem to be any fine-tuning. Our results suggest that the choice of Kobayashi-Maskawa angles is closely linked to the observed mass hierarchy. We close by discussing the corresponding case of neutrinos.

The properties of the Gribov region in $SU(2)$ Euclidean Yang-Mills theories in the maximal Abelian gauge are investigated. This region turns out to be bounded in all off-diagonal directions, while it is unbounded along the diagonal one. The soft breaking of the Becchi-Rouet-Stora-Tyutin invariance due to the restriction of the domain of integration in the path integral to the Gribov region is scrutinized. Owing to the unboundedness in the diagonal direction, the invariance with respect to Abelian transformations is preserved, a property which is at the origin of the local $U(1)$ Ward identity of the maximal Abelian gauge.

In this paper the structure of the next-to-leading order static gluon self-energy for an anisotropic plasma is investigated in the limit of a small momentum space anisotropy. Using the Ward identities for the static hard-loop (HL) gluon polarization tensor and the (nontrivial) static HL vertices, we derive a comparatively compact form for the complete next-to-leading order correction to the structure function containing the spacelike pole associated with magnetic instabilities. On the basis of a calculation without HL vertices, it has been conjectured that the imaginary part of this structure function is nonzero, rendering the spacelike poles integrable. We show that there are both positive and negative contributions when HL vertices are included, highlighting the necessity of a complete numerical evaluation, for which the present work provides the basis.

We study the standard-model extensions that have the following features: they violate Lorentz invariance explicitly at high energies; they are unitary, local, polynomial and renormalizable by weighted power counting; they contain the vertex $(LH{)}^2$, which gives Majorana masses to the neutrinos after symmetry breaking, and possibly four fermion interactions; they do not contain right-handed neutrinos, nor other extra fields. We study the simplest $CPT$ invariant standard-model extension of this type in detail and prove the cancellation of gauge anomalies. We investigate the low-energy recovery of Lorentz invariance and comment on other types of extensions.

We present a numerical investigation of the dynamics of symmetry breaking in both Abelian and non-Abelian $[SU(2)]$ Higgs models in three spatial dimensions. We find a class of time-dependent, long-lived nonperturbative field configurations within the range of parameters corresponding to type-1 superconductors, that is, with vector masses ($m_v$) larger than scalar masses ($m_s$). We argue that these emergent nontopological configurations are related to oscillons found previously in other contexts. For the Abelian-Higgs model, our lattice implementation allows us to map the range of parameter space—the values of $\beta =(m_s/m_v{)}^2$—where such configurations exist and to follow them for times $t\sim \mathcal{O}({10}^5)m^{-1}$. An investigation of their properties for $\widehat{z}$-symmetric models reveals an enormously rich structure of resonances and mode-mode oscillations reminiscent of excited atomic states. For the $SU(2)$ case, we present preliminary results indicating the presence of similar oscillonic configurations.