Search

I propose a unified model of particle physic and cosmology based on both a new extension of the standard particle model and the fundamental principle of the standard cosmology. Beyond the standard model, I introduce several species of dark fields with the dark symmetry of Z 2 ⊗ Z 2 ′ , the inflation field, cold dark matter (CDM) and dark energy (DE) are of course included among them. The model can coherently and completely describe the origin and evolution of the universe from the primordial inflation to the reheating, to the baryogenesis, to the current CDM and DE, and also the neutrino mass generation mechanism. For the energy evolution of each phase, I give its dynamical system of equations, and solve them by some special techniques. The numerical results can clearly show how each evolution is successfully implemented, furthermore, the model demonstrates that the DE genesis is purely from the CDM condensation, which is essentially a reverse process of the primordial slow-roll inflation, there is not the so-called "cosmological constant energy". By use of fewer input parameters, the model not only exactly reproduces the measured inflationary data and the current energy density budget, but also finely predicts such important values as the tensor-to-scalar ratio r 0. 0 5 ≈ 1. 6 8 × 1 0 − 6 , the inflaton mass M Φ ≈ 5. 0 5 × 1 0 1 0 GeV, the reheating temperature T r e ≈ 8. 2 9 × 1 0 1 0 GeV, the CDM mass M S ≈ 2 5 6 GeV, η B ≈ 6. 1 4 × 1 0 − 1 0 and h ≈ 0. 7 3 , in particular, the model smoothly clarifies and eliminates the "Hubble tension". In short, the unified model newly establishes the deeper and closer relations between particle physics and cosmology, therefore we expect the ongoing and future experiments to test the model. [ABSTRACT FROM AUTHOR]

We analyze the Axion Electrodynamics in a two-dimensional slab of finite width L containing a homogeneous and isotropic dielectric medium with constant permittivity and permeability. We start from the known decomposition of modes in the nonaxion case and then solve perturbatively the governing equations for the electromagnetic fields to which the axions are also coupled. This is a natural approach, since the finiteness of L destroys the spatial invariance of the theory in the z-direction normal to the plates. In this way, we derive the value of the axion-generated rotation angle of the electric and magnetic fields after their passage through the slab, and use the obtained results to calculate the Casimir force between the two conducting plates. Our calculations make use of the same method as previously outlined by [J. S. Høye and I. Brevik, Eur. Phys. J. Plus 135, 271 (2020)] for the case of Casimir calculations in chiral media and extend former results on the Casimir force in Axion Electrodynamics. [ABSTRACT FROM AUTHOR]

Axion Dark Matter (DM) is studied on the formation of SuperMassive Black Holes (SMBH) at high red shift z. It is shown that the attractive self-interaction of this DM may resolve the tension between the large mass with high angular momentum of SMBH and its early time formation. We consider the ultra-light axion DM around O (1 0 − 2 1) eV as its origin, which may also cause nano-Hz stochastic gravitational wave background recently observed. [ABSTRACT FROM AUTHOR]

The QCD (Quantum ChromoDynamics) axion emerged as one of the best-motivated dark matter candidates. In 2018, the Axion Dark Matter eXperiment (ADMX), one of the U.S. Department of Energy's "Gen 2" flagship dark-matter projects, demonstrated first sensitivity to the highly plausible "DFSZ" dark matter axion couplings over a small frequency range. We anticipate this development marks the first step in constructing yet more powerful experiments that can explore large swaths of the axion parameter space at high sensitivity and result in a discovery. But, realizing this requires advances in both our understanding of the theory and experiment design. Between 25 January and 27 January 2021, the "Axions Beyond Gen 2 Workshop" was held, where selected members of the community discussed our broad understanding of the QCD axion and charted a course for future experiments having sensitivity and mass reach well beyond the current "Gen 2" experiments. These proceedings are summaries of the topics presented and discussed. [ABSTRACT FROM AUTHOR]

The dynamics of spin in external electromagnetic, gravitational, and axion fields is analyzed in the framework of the gravitoelectromagnetism approach in Einstein's general relativity theory. We consistently extend the recent studies from the flat Minkowski geometry to the curved spacetime manifolds, contributing to the discussion of the possible new role of a precessing spin as an "axion antenna" that can be used to detect the hypothetical axion-like dark matter. The formalism developed helps to clarify the subtle influence of the gravitational/inertial and axion fields in the ultra-sensitive high-energy spin experiments with charged particles and neutrons at accelerators and storage rings devoted to testing fundamental physical symmetries, including attempts to establish the nature of dark matter in the Universe. [ABSTRACT FROM AUTHOR]

We study inflation in a model with constant second slow-roll parameter η. In this case, the Hubble expansion rate equation has analytical solutions describing four possible, nontrivial inflation scenarios. The evolution of the inflaton governed by a tachyon field is studied in the framework of the standard and Randall–Sundrum II cosmology. The attractor behavior of the solution is briefly demonstrated. Finally, the calculated values of the parameters n s and r are compared with observational data. [ABSTRACT FROM AUTHOR]

In this work, we examined chromo-natural inflation in the context of warm inflation with constant and variable dissipation coefficients. We studied the cosmological perturbation theory in this model and obtained the scalar and tensor power spectra in each case. The sources of density fluctuations in this model are mainly the thermal fluctuations of the inflaton field like a general warm inflationary model. Finally, cosmological observables, namely, the spectral index and tensor-to-scalar ratio are calculated. It is found that the cosmological observables are consistent with observational Planck 2018 and BICEP bounds for sub-Planckian values of axion decay constant f in case of temperature–inflaton-dependent dissipation coefficient. In case of the constant and temperature-dependent dissipation coefficient, the values of axion decay constant f can be lowered below the GUT scale. [ABSTRACT FROM AUTHOR]

We readdress the issue of strong CP violation both in the Standard Model (SM) and in the Minimal Left–Right (LR) Symmetric Model and try to clear the confusion that seems to still pervade the field. We argue that the smallness of strong CP violation, while harmless and basically decoupled from the rest of the physics in the SM, in the context of LR symmetry provides a blessing by helping to narrow down the parameter space of the theory and connecting apparently the uncorrelated physical quantities. In particular, in the context of left–right symmetry being parity, it either points to the suppression of leptonic CP violation noticed before, or leads to relatively light right-handed neutrinos, potentially accessible at the next hadron collider. The latter, more natural in view of complex quark Yukawa couplings, goes hand in hand with the smallness of lepton flavor violation and enhances the possibility of observing neutrinoless double-beta decay. [ABSTRACT FROM AUTHOR]

Axion electrodynamics is based upon the Lagrangian of the electromagnetic (EM) field plus its interaction with the axions, and is accordingly a physically open system. It means that the four-divergence of the EM energy–momentum tensor is different from zero, implying in turn that the total EM energy and momentum (when integrated over all space) do not constitute a four-vector. The EM force is in principle accessible to experimental detection, just analogous to what is the case in ordinary electrodynamics. In the first half of this paper the energy–momentum aspects of axion electrodynamics are worked out in general, when the surroundings are allowed to be a medium with constant permittivity and permeability. In the second half, two examples are discussed. The first is a static situation, where a block of uniform material containing axions is exposed to external strong electric and magnetic fields. Assuming the axion amplitude a (x) (i.e. its density) to increase linearly in one direction, we calculate the axion-generated forces. As a second example, we consider axions varying not with position but instead harmonically with time; this is the constellation usually assumed in astrophysics. Assuming a Gaussian profile for the EM wave emitted from the Earth towards an axion cloud in outer space, we make a calculation of the 'axion echo', the return signal. [ABSTRACT FROM AUTHOR]

Axion like particles (ALPs) and right-handed neutrinos (RHNs) are two well-motivated dark matter (DM) candidates. However, these two particles have a completely different origin. Axion was proposed to solve the strong CP problem, whereas RHNs were introduced to explain light neutrino masses through seesaw mechanisms. We study the case of ALP portal RHN DM (Majorana DM) taking into account existing constraints on ALPs. We consider the leading effective operators mediating interactions between the ALP and Standard Model (SM) particles and three RHNs to generate light neutrino masses through type-I seesaw. Further, ALP-RHN neutrino coupling is introduced to generalize the model which is restricted by the relic density and indirect detection constraint. [ABSTRACT FROM AUTHOR]

In this work, we carry out a study of the conserved quantities and dynamical structure of the four-dimensional modified axion electrodynamics theory described by the axion-photon coupling. In the first part of the analysis, we employ the covariant phase space method to construct the conserved currents and to derive the Noether charges associated with the gauge symmetry of the theory. We further derive the improved energy–momentum tensor using the Belinfante–Rosenfeld procedure, which leads us to the expressions for the energy, momentum, and energy flux densities. Thereafter, with the help of Faddeev–Jackiw's Hamiltonian reduction formalism, we obtain the relevant fundamental brackets structure for the dynamic variables and the functional measure for determining the quantum transition amplitude. We also confirm that modified axion electrodynamics has three physical degrees of freedom per space point. Moreover, using this symplectic framework, we yield the gauge transformations and the structure of the constraints directly from the zero-modes of the corresponding pre-symplectic matrix. [ABSTRACT FROM AUTHOR]

A bonus of the framed Standard Model (FSM), constructed initially to explain the mass and mixing patterns of quarks and leptons, is a solution (without axions) of the strong CP problem by cancelling the theta-angle term I Tr (H μ ν H μ ν ∗) in colour by a chiral transformation on a quark zero mode which is inherent in FSM, and produces thereby a CP-violating phase in the CKM matrix similar in size to what is observed.1 Extending here to flavour, one finds that there are two terms proportional to Tr (G μ ν G μ ν ∗) : (a) in the action from flavour instantons with unknown coefficient, say I ′ , (b) induced by the above FSM solution to the strong CP-problem with therefore known coefficient C ′ . Both terms can be cancelled in the FSM by a chiral transformation on the lepton zero mode to give a Jarlskog invariant J ′ in the PMNS matrix for leptons of order 1 0 − 2 , as is hinted by the experiment. But if, as suggested in Ref. 2, the term I ′ is to be cancelled by a chiral transformation in the predicted hidden sector to solve the strong CP problem therein, leaving only the term C ′ to be cancelled by the chiral transformation on leptons, then the following prediction results: J ′ ∼ − 0. 0 1 2 (δ CP ′ ∼ (1. 1 1) π) which is (i) of the right order, (ii) of the right sign and (iii) in the range favoured by the present experiment. Together with the earlier result for quarks, this offers an attractive unified treatment of all known CP physics. a We use F μ ν , G μ ν and H μ ν here to denote, respectively the u (1) , flavour s u (2) and colour s u (3) gauge fields. [ABSTRACT FROM AUTHOR]

A limiting algebraic resonance seems to recuperate the pseudo-scalar Higgs from the simultaneous breaking process. On an energy kernel consideration, an imposed nonharmonic boundary exclusion provides a basis for the scaling (proved derived from the conformal classes) of its extending as radiative correction diagrams, plus whose anomalies eliminate upon reaching geometrically a type of steep power as linked to, completely from the curvature. A CP violating form, then shows after the appearance of both a parity, plus a polarization defiance, together with the Higgs decoupled to the favor of the equivalence class for a scalar coupling, leading to the types of allowed UV fixed points, with the possible fading of some of its parametric resonances (tachyon) by quantum corrections, into then the estimation of consecutive QCD and fuzzy axion masses by taking into account that their interaction (dimensional) operators such which have the completeness, both of metric and/or gauge types, being so then, first with KSVZ (showing as being resonant along with sterile neutrinos) and DFS types or second with creation of an axion soliton. The fit into the phenomenological constraints is also checked. [ABSTRACT FROM AUTHOR]

QCD axions are at the crossroads of QCD topology and Dark Matter searches. We present here the current status of topological studies on the lattice, and their implication on axion physics. We outline the specific challenges posed by lattice topology, the different proposals for handling them, the observable effects of topology on the QCD spectrum and its interrelation with chiral and axial symmetries. We review the transition to the quark–gluon plasma, the fate of topology at the transition, and the approach to the high temperature limit. We discuss the extrapolations needed to reach the regime of cosmological relevance, and the resulting constraints on the QCD axion. [ABSTRACT FROM AUTHOR]

We propose the pure natural quintessential inflation model which is motivated by Witten's conjecture, where the axion couples to pure Yang–Mills S U (N) gauge field at large N limit. This modifies the standard cosine potential which is presented in the natural inflation, making it compatible with current CMB data. Our model gives a successful inflation as well as acceleration at the late times by quintessence inflaton field (ϕ). Here the inflaton field is responsible for inflation, after that the field enters into peculiar type of reheating and then they act as dynamical dark energy field which follows the same inflation potential and same model parameters. The dynamical field slowly rolls until the Hubble drops to mass of the quintessence field and it reaches the current dark energy field value. Here the dark energy scale is field dependent. Our quintessence model follows thawing frozen approach, therefore the frozen quintessence field evolves with respect to cosmic time from initial field value (ϕ i) to present nonzero minimum field value (ϕ 0). The obtained field value turned into ultralight and it satisfies the present dark energy density which is V (ϕ 0) ≈ Λ DE 4 = (2. 3 × 1 0 − 3 eV) 4 . [ABSTRACT FROM AUTHOR]

In connection with the problem of dark matter, we discuss recent results on constraining the parameters of axion-to-nucleon interaction following from the experiment on measuring the difference of Casimir forces. It is shown that this experiment not only leads to competitive constraints, but provides stronger support to other constraints obtained in Casimir physics so far. The description of dark energy by means of cosmological constant originated from the quantum vacuum is considered in terms of the renormalization procedures in quantum field theory. It is argued that only the renormalized value of cosmological constant directly connected with the observed density of dark energy is of physical significance, so that some statements in the literature concerning the vacuum catastrophe may be considered as an exaggeration. [ABSTRACT FROM AUTHOR]

We study the production of gravitational waves from primordial scalar perturbations in a string axion inflationary model with subleading nonperturbative corrections. In such a model, the subleading nonperturbative effects can superimpose steep cliffs and gentle plateaus onto the leading axion potential. Such an inflationary potential both matches the Planck observations at CMB scales and gives rise to an enhancement in the scalar power spectrum at small scales. We calculate the second-order gravitational wave signatures induced by the scalar density perturbations, and find that the signal can be detected by the space-based laser interferometers in the future. [ABSTRACT FROM AUTHOR]

We study the interplay among extrema of axion potentials, Kahler moduli stabilization and the swampland criteria. We argue that moving away from the minima of nonperturbatively generated axion potentials can lead to a runaway behavior of moduli that govern the couplings in the effective field theory. The proper inclusion of these degrees of freedom resolves the conflict between periodic axion potentials and the gradient de Sitter criterion, without the need to invoke the refined de Sitter criterion. We investigate the possibility of including this runaway direction as a model of quintessence that satisfies the swampland criteria. Using a single nonperturbative effect, the maximum along the axion direction provides such a runaway direction, which is unstable in the axion directions, sensitive to initial conditions and too steep to allow for a Hubble time of expansion without violating the field excursion criterion. Adding a second nonperturbative effect generates a saddle point in the potential satisfying the refined de Sitter criterion, which solves the steepness problem and improves the initial conditions problem although some fine-tuning remains required. [ABSTRACT FROM AUTHOR]

We study a spontaneously broken Einstein–Yang–Mills–Higgs model coupled via a Higgs portal to an uncharged scalar χ. We present a phase diagram of self-gravitating solutions showing that depending on the choice of parameters of the χ scalar potential and the Higgs portal coupling constant γ , one can identify different regions: If γ is sufficiently small, a χ halo is created around the monopole core which in turn surrounds a black hole. For larger values of γ , no halo exists and the solution is just a black hole monopole one. When the horizon radius grows and becomes larger than the monopole radius, solely a black hole solution exists. Because of the presence of the χ scalar, a bound for the Higgs potential coupling constant exists and when it is not satisfied, the vacuum is unstable and no nontrivial solution exists. We briefly comment on possible connections of our results with those found in recent dark matter axion models. [ABSTRACT FROM AUTHOR]

Inspired by recent studies of high-scale decay constant or flavorful QCD axions, we review and clarify their existence in effective string models with anomalous U(1) gauge groups. We find that such models, when coupled to charged scalars getting vacuum expectation values, always have one light axion, whose mass can only come from nonperturbative effects. If the main nonperturbative effect is from QCD, then it becomes a Peccei–Quinn axion candidate for solving the strong CP problem. We then study simple models with universal Green–Schwarz mechanism and only one charged scalar field: in the minimal gaugino condensation case the axion mass is tied to the supersymmetry breaking scale and cannot be light enough, but slightly refined models maintain a massless axion all the way down to the QCD scale. Both kinds of models can be extended to yield intermediate scale axion decay constants. Finally, we gauge flavorful axion models under an anomalous U(1) and discuss the axion couplings which arise. [ABSTRACT FROM AUTHOR]

The axions and axion-like particles can be detected via a resonant atomic or molecular transition induced by axion absorption. The signal obtained in this process is second order in the axion-electron interaction constant and hence small. In this chapter, it is demonstrated that this signal may become first order in the axion-electron interaction constant if we allow the interference between the axion-induced transition amplitude and the transition amplitude induced by the electromagnetic radiation. Additionally, we show that the conventional scheme of producing axions from photons in a magnetic field may be improved if the field is replaced by an atomic medium in which photons scattering off the atoms in the forward direction are transformed into axions. [ABSTRACT FROM AUTHOR]

It is discussed how the ideas of entropy and the second law of thermodynamics, conceived long ago during the nineteenth century, underly why cosmological dark matter exists and originated in the first three years of the universe in the form of primordial black holes, a very large number of which have many solar masses including up to the supermassive black holes at the centres of galaxies. Certain upper bounds on dark astrophysical objects with many solar masses based on analysis of the CMB spectrum and published in the literature are criticised. For completeness we discuss WIMPs and axions which are leading particle theory candidates for the constituents of dark matter. The PIMBHs (Primordial Intermediate Mass Black Holes) with many solar masses should be readily detectable in microlensing experiments which search the Magallenic Clouds and measure light curves with durations of from one year up to several years. [ABSTRACT FROM AUTHOR]

I study a class of Randall–Sundrum (RS) models with Spontaneous Breaking of Scale Invariance (SBSI). This class of models implements the Contino–Pomarol–Rattazzi (CPR) mechanism to achieve SBSI through the small running of an external close-to-marginal scale-breaking operator that leads to a light dilaton/radion with couplings to matter suppressed by the small running. I show that for radion masses ≲ 1  KeV, it can serve as a dark matter (DM) candidate, with a lifetime longer than the age of the universe, and show that the experimental bounds from LHC, non-Newtonian gravity and Axion-Like Particle (ALP) searches allow for the existence of such a radion. In spite of the small relic abundance of the light radion produced in this model, we show that it could be possible to obtain the required abundance through additional assumptions, an issue we postpone to the future. [ABSTRACT FROM AUTHOR]

In recent years, a new field emerged in dark matter community and immediately attracted a multitude of theorists and experimentalists, that of light dark matter direct detection in electronic systems. The phenomenon is similar to nuclear recoil in elastic scattering between dark matter and nucleus but with different kinematics. Due to the small energy gap, the electronic system can probe sub-GeV dark matter rather than nucleus target. In particular, the absorption into materials can even detect ultralight dark matter within mass around meV. In terms of the equivalence between optical conductivity and absorption cross-section, axion detection can be computed in Bismuth-based topological insulators. It is found that topological insulator has strong sensitivity on axion and provides a complementary direct detection to superconductor and semiconductors. The novelty of topological insulator is that the thin film could even obtain the same sensitivity as a superconductor. [ABSTRACT FROM AUTHOR]

Pseudoscalars appearing in particle physics are reviewed systematically. From the fundamental point of view at an ultraviolet completed theory, they can be light if they are realized as pseudo-Goldstone bosons of some spontaneously broken global symmetries. The spontaneous breaking scale is parametrized by the decay constant . The global symmetry is defined by the lowest order terms allowed in the effective theory consistent with the gauge symmetry in question. Since any global symmetry is known to be broken at least by quantum gravitational effects, all pseudoscalars should be massive. The mass scale is determined by and the explicit breaking terms in the effective potential and also anomaly terms for some non-Abelian gauge groups . The well-known example by non-Abelian gauge group breaking is the potential for the 'invisible' QCD axion, via the Peccei-Quinn symmetry, which constitutes a major part of this review. Even if there is no breaking terms from gauge anomalies, there can be explicit breaking terms in the potential in which case the leading term suppressed by determines the pseudoscalar mass scale. If the breaking term is extremely small and the decay constant is trans-Planckian, the corresponding pseudoscalar can be a candidate for a 'quintessential axion.' In general, is considered to be smaller than , and hence the pseudo-Goldstone boson mass scales are considered to be smaller than the decay constants. In such a case, the potential of the pseudo-Goldstone boson at the grand unification scale is sufficiently flat near the top of the potential that it can be a good candidate for an inflationary model, which is known as 'natural inflation.' We review all these ideas in the bosonic collective motion framework. [ABSTRACT FROM AUTHOR]

We explore the generation of large-scale magnetic fields in the so-called moduli inflation. The hypercharge electromagnetic fields couple to not only a scalar field but also a pseudoscalar one, so that the conformal invariance of the hypercharge electromagnetic fields can be broken. We explicitly analyze the strength of the magnetic fields on the Hubble horizon scale at the present time, the local non-Gaussianity of the curvature perturbations originating from the massive gauge fields, and the tensor-to-scalar ratio of the density perturbations. As a consequence, we find that the local non-Gaussianity and the tensor-to-scalar ratio are compatible with the recent Planck results. [ABSTRACT FROM AUTHOR]

If axion-like particles (ALPs) constitute a major part of dark matter (DM), due to their bosonic nature and a relatively small mass, they could behave differently from the pointlike dark matter particles on the formation of the cosmic structures. When studying the structure formation, it is often useful to consider DM as a special fluid with a given density and a given velocity. ALP fluid obeys the same continuity equation compared to the pointlike collisionless DM, but has a different first-order velocity equation. In the linear regime of structure formation, the resulted observational differences are negligible for the QCD axions but can be interesting for very light ALPs. [ABSTRACT FROM AUTHOR]

Development of low radioactive technique allows to investigate many other rare nuclear and subnuclear processes: double decay, rare and decays, and to search for hypothetical particles and processes like axions, charge nonconserving decays, the nucleon, di-nucleon and tri-nucleon decays into invisible channels, to test the Pauli principle. Here, we present results of the rare processes searches and development of instrumentation for low counting experiments. [ABSTRACT FROM AUTHOR]

We consider recent progress in constraining the axion-nucleon coupling constants and the Yukawa-type corrections to Newtonian gravity from experiments on measuring the Casimir interaction. After a brief review of previously obtained constraints, we concentrate on the new Casimir-less experiment, which allows to strengthen the known results up to factors of 60 and 1000 for the axion-like particles and Yukawa-type corrections, respectively. We also discuss possibilities allowing to further strengthen the constraints on axion-nucleon coupling constants, and propose a new experiment aiming to achieve this goal. [ABSTRACT FROM AUTHOR]

We discuss the astronomical methods of searching for light Goldstone bosons (axions and arions). The basic idea is to use processes of coupling between axions and photons: a) the axion decay into two photons; b) the transformation process of photons into axions (arions) in the magnetic fields of stars and also of interstellar and intergalactic media; c) the inverse process of transformations of axions (arions) which are generated into cores of stars into X-ray photons. The decaying axions affect upon the diffuse extragalactic background radiation, the brightness of the night sky and especially on the intergalactic light of clusters of galaxies due to generation of the axion radiative decay emission line. The processes (b) and (c) are strongly dependent on polarization state of photon and may produce a noticeable amount of linear polarization. [ABSTRACT FROM AUTHOR]

In this work, we analyze the propagation of photons in an environment where a strong magnetic field (perpendicular to the photon momenta) coexists with an oscillating cold axion background with the characteristics expected from dark matter in the galactic halo. Qualitatively, the main effect of the combined background is to produce a three-way mixing among the two photon polarizations and the axion. It is interesting to note that in spite of the extremely weak interaction of photons with the cold axion background, its effects compete with those coming from the magnetic field in some regions of the parameter space. We determine (with one plausible simplification) the proper frequencies and eigenvectors as well as the corresponding photon ellipticity and induced rotation of the polarization plane that depend both on the magnetic field and the local density of axions. We also comment on the possibility that some of the predicted effects could be measured in optical table-top experiments. [ABSTRACT FROM AUTHOR]

The axion is a light pseudoscalar particle which suppresses CP-violating effects in strong interactions and also happens to be an excellent dark matter candidate. Axions constituting the dark matter halo of our galaxy may be detected by their resonant conversion to photons in a microwave cavity permeated by a magnetic field. The current generation of the microwave cavity experiment has demonstrated sensitivity to plausible axion models, and upgrades in progress should achieve the sensitivity required for a definitive search, at least for low mass axions. However, a comprehensive strategy for scanning the entire mass range, from 1-1000 μeV, will require significant technological advances to maintain the needed sensitivity at higher frequencies. Such advances could include sub-quantum-limited amplifiers based on squeezed vacuum states, bolometers, and/or superconducting microwave cavities. The Axion Dark Matter eXperiment at High Frequencies (ADMX-HF) represents both a pathfinder for first data in the 20-100 μeV range (~5-25 GHz), and an innovation test-bed for these concepts. [ABSTRACT FROM AUTHOR]

It is shown that an alternative to the standard scalar quantum electrodynamics (QED) is possible. In this new version, there is only global gauge invariance as far as the charged scalar fields are concerned, although local gauge invariance is kept for the electromagnetic field. The electromagnetic coupling has the form jμ(Aμ +∂μB) where B is an auxiliary field and the current jμ is Aμ independent, so that no "sea gull terms" are introduced. As a consequence of the absence of sea gulls, it is seen that no Klein paradox appears in the presence of a strong square well potential. In a model of this kind, spontaneous breaking of symmetry does not lead to photon mass generation, instead the Goldstone boson becomes a massless source for the electromagnetic field. When spontaneous symmetry breaking takes place infrared questions concerning the theory and generalizations to global vector QED are discussed. In this framework, Q-Balls and other nontopological solitons that owe their existence to a global U(1) symmetry can be coupled to electromagnetism and could represent multiply charged particles now in search in the large hadron collider (LHC). Furthermore, we give an example where an "Emergent" Global Scalar QED can appear from an axion-photon system in an external magnetic field. Finally, formulations of Global Scalar QED that allow perturbative expansions without sea gulls are developed. [ABSTRACT FROM AUTHOR]

In 2001, a supersymmetric model was proposed to relate the axion scale to that of neutrino mass seesaw. Whereas this scenario is realistic, the particles associated with this mechanism are either too heavy or too weakly coupled for them to be observed (other than the axion itself or perhaps the axino). A variation of that model is here proposed which allows significant mixing of the Higgs boson with a new singlet related to the saxion (the scalar partner of the pseudoscalar axion), rendering it possible to be observed at the large hadron collider (LHC). With the addition of exotic color superfields, this also becomes a specific realization of how the production of such a Higgs hybrid may be suppressed or enhanced at the LHC, which is very relevant to ongoing experimental efforts to find the Higgs boson. [ABSTRACT FROM AUTHOR]

For a Podolsky-axionic electrodynamics, we compute the interaction potential within the structure of the gauge-invariant but path-dependent variables formalism. The result is equivalent to that of axionic electrodynamics from a new noncommutative approach, up to first-order in θ. [ABSTRACT FROM AUTHOR]

We study the 2D scattering of axions from an accelerator like quadrupole magnet using the eikonal approximation in order to learn whether or not such a setup could serve as a new possible method for detecting axions on terrestrial experiments. The eikonal approximation in 2D is introduced and explained. We also apply the eikonal approximation to two known cases in order to compare it with previous results, obtained using Born's approximation, and discuss its correctness. [ABSTRACT FROM AUTHOR]

We study the connection or equivalence between two well-known extensions of the Standard Model, that is, for the coupling between the familiar massless electromagnetism U(1)QED and a hidden-sector U(1)h, and axionic electrodynamics. Our discussion is carried out using the gauge-invariant but path-dependent variables formalism, which is an alternative to the Wilson loop approach. When we compute in this way the static quantum potential for the coupling between the familiar massless electromagnetism U(1)QED and a hidden-sector U(1)h, the result of this calculation is a Yukawa correction to the usual static Coulomb potential. Previously,14, we have shown that axionic electrodynamics has a different structure which is reflected in a confining piece. Therefore, both extensions of the Standard Model are not equivalent. Interestingly, when the above calculation is done inside a superconducting box, the Coulombic piece disappears leading to a screening phase. [ABSTRACT FROM AUTHOR]

The hypothesis of an 'invisible' axion was made by Misha Shifman and others, approximately thirty years ago. It has turned out to be an unusually fruitful idea, crossing boundaries between particle physics, astrophysics and cosmology. An axion with mass of order 10-5 eV (with large uncertainties) is one of the leading candidates for the dark matter of the universe. It was found recently that dark matter axions thermalize and form a Bose-Einstein condensate (BEC). Because they form a BEC, axions differ from ordinary cold dark matter (CDM) in the non-linear regime of structure formation and upon entering the horizon. Axion BEC provides a mechanism for the production of net overall rotation in dark matter halos, and for the alignment of cosmic microwave anisotropy multipoles. Because there is evidence for these phenomena, unexplained with ordinary CDM, an argument can be made that the dark matter is axions. [ABSTRACT FROM AUTHOR]

I consider models of light super-weakly interacting cold dark matter, with ${\cal O}(10)\,\,{\rm{keV}}$ mass, focusing on bosonic candidates such as pseudoscalars and vectors. I analyze the cosmological abundance, the γ-background created by particle decays, the impact on stellar processes due to cooling, and the direct detection capabilities in order to identify classes of models that pass all the constraints. In certain models, variants of photoelectric (or axioelectric) absorption of dark matter in direct-detection experiments can provide a sensitivity to the superweak couplings to the Standard Model which is superior to all existing indirect constraints. In all models studied, the annual modulation of the direct-detection signal is at the currently unobservable level of O(10-5). [ABSTRACT FROM AUTHOR]

The interaction of a fermion with the dense axion medium is investigated for the purpose of finding an axion medium effect on the fermion dispersion. It is shown that axion medium influence on the fermion dispersion under astrophysical conditions is negligible small if the correct Lagrangian of the axion–fermion interaction is used. [ABSTRACT FROM AUTHOR]

D-brane realizations of the Standard Model predict extra abelian gauge fields which are superficially anomalous. The anomalies are cancelled via appropriate couplings to axions and Chern-Simons-like couplings. The presence of such couplings has dramatic experimental consequences: a) they provide masses to the anomalous abelian gauge fields (which masses can be of order of a few TeV), b) they provide new contributions to couplings like Z'-¿gammaZ, that may be considerable at LHC. This proceeding is mainely based on hep-th/0605225. [ABSTRACT FROM AUTHOR]

Inflationary models with a superheavy scale F-term hybrid inflation followed by an intermediate scale modular inflation are considered. The restrictions on the power spectrum $P_{\mathcal R}$ of curvature perturbation and the spectral index ns from the recent data within the power-law cosmological model with cold dark matter and a cosmological constant can be met provided that the number of e-foldings NHI* suffered by the pivot scale k* = 0.002/Mpc during hybrid inflation is suitably restricted. The additional e-foldings needed for solving the horizon and flatness problems are generated by modular inflation with a string axion as inflaton. For central values of $P_{\mathcal R}$ and ns, the grand unification scale comes out, in the case of standard hybrid inflation, close to its supersymmetric value MGUT ≃ 2.86 × 1016GeV, the relevant coupling constant is relatively large (≈ 0.005 – 0.14), and 10 ≲ NHI* ≲ 21.7. In the shifted [smooth] hybrid inflation case, the grand unification scale can be identified with MGUT for NHI* ≃ 21 [NHI* ≃ 18]. [ABSTRACT FROM AUTHOR]

The modular invariance of the one-loop partition function of the closed bosonic string in four dimensions in the presence of certain homogeneous exact pp-wave backgrounds is studied. In the absence of an axion field, the partition function is found to be modular invariant and equal to the free field partition function. The partition function remains unchanged also in the presence of a fixed axion field. However, in this case, the covariant form of the action suggests summation over all possible twists generated by the axion field. This is shown to modify the partition function. In the light-cone gauge, the axion field generates twists only in the worldsheet σ-direction, so the resulting partition function is not modular invariant, hence wrong. To obtain the correct partition function one needs to sum over twists in the t-direction as well, as suggested by the covariant form of the action away from the light-cone gauge. [ABSTRACT FROM AUTHOR]

The cosmological (upper) limit on the Peccei-Quinn constant, related to the primordial oscillations of the axion field, can be relaxed for a mirror axion model. The simple reason is that the mirror world is colder and so the behavior of the axion temperature-dependent mass is dominated by the contribution from the mirror sector. So the coherent oscillations start earlier and correspondingly the axion mass density Ωah2 is reduced. [ABSTRACT FROM AUTHOR]

The axion–dilaton string effective action is expressed in Einstein frame metric in a manifestly S-duality invariant form. It is shown that the moduli can be redefined to describe surface of a (2+1)-dimensional pseudosphere. The classical cosmological solutions of axion–dilaton are revisited. The Wheeler–DeWitt equation for the system is exactly solved and complete set of eigenfunctions are presented. The wave function factorizes and the one depending on the moduli is obtained by appealing to the underlying S-duality symmetry. Axion and dilaton parametrize $\frac{{\rm SU}(1,1)}{{\rm U}(1)}$, the S-duality group, and the Hamiltonian is expressed as a sum of the Ricci scalar and the Casimir of SU(1, 1). Therefore, the complete set of wave functions, depending on the moduli, is obtained from group theory technique. The evidence for the existence of a W-infinity algebra in axion–dilaton cosmology is presented and the origin of the algebra is primarily due to high degree of degeneracies in the wave functions. It is qualitatively argued that axion–dilaton quantum cosmology exhibits chaotic behavior in the semiclassical limit. [ABSTRACT FROM AUTHOR]

A deeper understanding of the vacuum structure in QCD invites one to rethink certain aspects of axion physics. The recent advances are mostly due to developments in supersymmetric gauge theories and the brane theory, in which QCD can be embedded. They include, but are not limited to, the studies of metastable vacua in multicolor gluodynamics, and the domain walls. We briefly review basics of axion physics and then present a modern perspective on a rich interplay between the QCD vacuum structure and axion physics. [ABSTRACT FROM AUTHOR]

The theoretical existence of oscillating boson stars consisting of a real scalar field, stable to radial perturbations, has been proven by Seidel and Suen. For the QCD axion of the heterotic superstring theory, this implies a mini-star of mass M ≈ 10[sup -2] (1 +λ²)[sup ¾]g³[sub s] M⊙, where λ ≡ f[sub a']/f[sub a] is the ratio of the decay constants of the second and model-independent axions, which, for a suitable value in the range 1 ... λ ... 10, can explain the astronomical microlensing observations towards the Galactic centre and the Large and Small Magellanic Clouds. Here, we apply the non-linear relaxation theory developed by Tkachev to show that the condition τ[sub f] < τ[sub r] < τ[sub 0] for the formation of such an object, where τ[sub f], τ[sub r] and &tai;[sub 0] are the free-fall and relaxation times and the age of the Universe, respectively, leads to the condition 5 × 10[sup -2]C[sup -1/3](1 + λ²)[sup 5/12]g[sup 5/3, sub s] ... M/M⊙ ... 10[sup 4] C[sup -1/4](1 + λ²)[sup ½g&sup2, sub s], where g²[sub s] ≈ 1.4 is the strong-interaction coupling parameter and C is a dimensionless constant defined below. From this, we argue, considering the approximations involved, that the star does condense. [ABSTRACT FROM AUTHOR]

Photon-axion conversions in static magnetic fields and in a periodic field with frequency equal to the axion mass are considered in detail by the Feynman diagram methods. The differential cross-sections are presented and numerical evaluations are given. It is shown that there is a resonant conversion for the considered process. Some estimates for experimental conditions are given from our results. [ABSTRACT FROM AUTHOR]