A UA(1) symmetry restoration scenario supported by the generalized Witten–Veneziano relation and its analytic solution

The Witten–Veneziano relation, or, alternatively, its generalization proposed by Shore, facilitates understanding and describing the complex of η and η′ mesons. We present an analytic, closed-form solution to Shore's equations which gives results on the η – η′ complex in full agreement with results previously obtained numerically. Although the Witten–Veneziano relation and Shore's equations are related, the ways they were previously used in the context of dynamical models to calculate η and η′ properties, were rather different. However, with the analytic solution, the calculation can be formulated similarly to the approach through the Witten–Veneziano relation, and with some conceptual improvements. In the process, one strengthens the arguments in favor of a possible relation between the UA(1) and SUA(3) chiral symmetry breaking and restoration. To test this scenario, the experiments such as those at RHIC, NICA and FAIR, which extend the RHIC (and LHC) high-temperature scans also to the finite-density parts of the QCD phase diagram, should pay particular attention to the signatures from the η′ – η complex indicating the symmetry restoration

Majorana dark matter in a classically scale invariant model

We analyze a classically scale invariant extension of the Standard Model with a dark gauge U(1) X broken by a doubly charge scalar Φ leaving a remnant Z 2 symmetry. Dark fermions are introduced as dark matter candidates and for anomaly reasons we introduce two chiral fermions. Due to classical scale invariance, bare mass term that would mix these two states is absent and they end up as stable Majorana fermions N 1 and N 2 . We calculate cross sections for N a N a → ϕϕ, N a N a → X μ ϕ and N 2 N 2 → N 1 N 1 annihilation channels. We put constraints to the model from the Higgs searches at the LHC, dark matter relic abundance and dark matter direct detection limits by LUX. The dark gauge boson plays a crucial role in the Coleman-Weinberg mechanism and has to be heavier than 680 GeV. The viable mass region for dark matter is from 470 GeV up to a few TeV. In the case when the two Majorana fermions have different masses, two dark matter signals at direct detection experiments could provide a distinctive signature of this model

Scotogenic RνMDM at three-loop level

We propose a model in which the radiative neutrino ( Rν ) masses are induced by fermion quintuplet and scalar septuplet fields from the minimal-dark-matter (MDM) setup. In conjunction with the 2HDM fields, on top of which our model is built, these hypercharge zero fields and additional scalar quintuplet lead to an accidental DM-protecting Z2 symmetry and establish the RνMDM model at the three-loop level. We assess the potential for discovery of quintuplet fermions on present and future pp colliders

Radiative neutrino mass with scotogenic scalar triplet

We present a radiative one-loop neutrino mass model with hypercharge zero scalar triplet in conjunction with another charged singlet scalar and an additional vectorlike lepton doublet. We study three variants of this mass model: the first one without additional beyond-SM symmetry, the second with imposed DM-stabilizing discrete <math altimg="si1.gif" xmlns="http://www.w3.org/1998/Math/MathML"><msub><mrow><mi>Z</mi></mrow><mrow><mn>2</mn></mrow></msub></math> symmetry, and the third in which this <math altimg="si1.gif" xmlns="http://www.w3.org/1998/Math/MathML"><msub><mrow><mi>Z</mi></mrow><mrow><mn>2</mn></mrow></msub></math> symmetry is promoted to the gauge symmetry <math altimg="si2.gif" xmlns="http://www.w3.org/1998/Math/MathML"><mi>U</mi><msub><mrow><mo stretchy="false">(</mo><mn>1</mn><mo stretchy="false">)</mo></mrow><mrow><mi>D</mi></mrow></msub></math> . The two latter cases are scotogenic, with a neutral component of the scalar triplet as a dark matter candidate. In first scotogenic model the <math altimg="si1.gif" xmlns="http://www.w3.org/1998/Math/MathML"><msub><mrow><mi>Z</mi></mrow><mrow><mn>2</mn></mrow></msub></math> -odd dark matter candidate is at the multi-TeV mass scale, so that all new degrees of freedom are beyond the direct reach of the LHC. In second scotogenic setup, with broken <math altimg="si2.gif" xmlns="http://www.w3.org/1998/Math/MathML"><mi>U</mi><msub><mrow><mo stretchy="false">(</mo><mn>1</mn><mo stretchy="false">)</mo></mrow><mrow><mi>D</mi></mrow></msub></math> symmetry the model may have LHC signatures or be relevant to astrophysical observations, depending on the scale of <math altimg="si2.gif" xmlns="http://www.w3.org/1998/Math/MathML"><mi>U</mi><msub><mrow><mo stretchy="false">(</mo><mn>1</mn><mo stretchy="false">)</mo></mrow><mrow><mi>D</mi></mrow></msub></math> breaking

Avoiding Boltzmann Brain domination in holographic dark energy models

In a spatially infinite and eternal universe approaching ultimately a de Sitter (or quasi-de Sitter) regime, structure can form by thermal fluctuations as such a space is thermal. The models of Dark Energy invoking holographic principle fit naturally into such a category, and spontaneous formation of isolated brains in otherwise empty space seems the most perplexing, creating the paradox of Boltzmann Brains (BB). It is thus appropriate to ask if such models can be made free from domination by Boltzmann Brains. Here we consider only the simplest model, but adopt both the local and the global viewpoint in the description of the Universe. In the former case, we find that if a dimensionless model parameter c , which modulates the Dark Energy density, lies outside the exponentially narrow strip around the most natural c=1 line, the theory is rendered BB-safe. In the latter case, the bound on c is exponentially stronger, and seemingly at odds with those bounds on c obtained from various observational tests

Electroweak breaking and Dark Matter from the common scale

We propose a classically scale invariant extension of the Standard Model where the electroweak symmetry breaking and the mass of the Dark Matter particle come from the common scale. We introduce <math altimg="si1.gif" xmlns="http://www.w3.org/1998/Math/MathML"><mi>U</mi><msub><mrow><mo stretchy="false">(</mo><mn>1</mn><mo stretchy="false">)</mo></mrow><mrow><mi>X</mi></mrow></msub></math> gauge symmetry and X -charged scalar Φ and Majorana fermion N . Scale invariance is broken via Coleman–Weinberg mechanism providing the vacuum expectation value of the scalar Φ . Stability of the dark matter candidate N is guaranteed by a remnant <math altimg="si2.gif" xmlns="http://www.w3.org/1998/Math/MathML"><msub><mrow><mi>Z</mi></mrow><mrow><mn>2</mn></mrow></msub></math> symmetry. The Higgs boson mass and the mass of the Dark Matter particle have a common origin, the vacuum expectation value of Φ . Dark matter relic abundance is determined by annihilation <math altimg="si3.gif" xmlns="http://www.w3.org/1998/Math/MathML"><mi>N</mi><mi>N</mi><mo stretchy="false">→</mo><mi>Φ</mi><mi>Φ</mi></math> . We scan the parameter space of the model and find the mass of the dark matter particle in the range from 500 GeV to a few TeV

Analog geometry in an expanding fluid from AdS/CFT perspective

The dynamics of an expanding hadron fluid at temperatures below the chiral transition is studied in the framework of AdS/CFT correspondence. We establish a correspondence between the asymptotic AdS geometry in the 4+1 dimensional bulk with the analog spacetime geometry on its 3+1 dimensional boundary with the background fluid undergoing a spherical Bjorken type expansion. The analog metric tensor on the boundary depends locally on the soft pion dispersion relation and the four-velocity of the fluid. The AdS/CFT correspondence provides a relation between the pion velocity and the critical temperature of the chiral phase transition

Violation of unitarity by Hawking radiation does not violate energy-momentum conservation

An argument by Banks, Susskind and Peskin (BSP), according to which violation of unitarity would violate either locality or energy-momentum conservation, is widely believed to be a strong argument against non-unitarity of Hawking radiation. We find that the whole BSP argument rests on the crucial assumption that the Hamiltonian is not highly degenerate, and point out that this assumption is not satisfied for systems with many degrees of freedom. Using Lindblad equation, we show that high degeneracy of the Hamiltonian allows local non-unitary evolution without violating energy-momentum conservation. Moreover, since energy-momentum is the source of gravity, we argue that energy-momentum is necessarily conserved for a large class of non-unitary systems with gravity. Finally, we explicitly calculate the Lindblad operators for non-unitary Hawking radiation and show that they conserve energy-momentum

Toward the classification of differential calculi on κ -Minkowski space and related field theories

Classification of differential forms on κ -Minkowski space, particularly, the classification of all bicovariant differential calculi of classical dimension is presented. By imposing super-Jacobi identities we derive all possible differential algebras compatible with the κ -Minkowski algebra for time-like, space-like and light-like deformations. Embedding into the super-Heisenberg algebra is constructed using non-commutative (NC) coordinates and one-forms. Particularly, a class of differential calculi with an undeformed exterior derivative and one-forms is considered. Corresponding NC differential calculi are elaborated. Related class of new Drinfeld twists is proposed. It contains twist leading to κ -Poincaré Hopf algebra for light-like deformation. Corresponding super-algebra and deformed super-Hopf algebras, as well as the symmetries of differential algebras are presented and elaborated. Using the NC differential calculus, we analyze NC field theory, modified dispersion relations, and discuss further physical applications

Effects of Noncommutativity on the Black Hole Entropy

The BTZ black hole geometry is probed with a noncommutative scalar field which obeys the κ-Minkowski algebra. The entropy of the BTZ black hole is calculated using the brick wall method. The contribution of the noncommutativity to the black hole entropy is explicitly evaluated up to the first order in the deformation parameter. We also argue that such a correction to the black hole entropy can be interpreted as arising from the renormalization of the Newton’s constant due to the effects of the noncommutativity