Right-handed States Research Articles

The new \u03bdMSM (\u03bd\u03bdMSM): radiative neutrino masses, keV-scale dark matter and viable leptogenesis with sub-TeV new physics

We study the scenario in which the Standard model is augmented by three generations of right-handed neutrinos and a scalar doublet. The newly introduced fields share an odd charge under a ℤ2 parity symmetry. This model, commonly known as “Scotogenic”, was designed to provide a mechanism for active neutrino mass generation as well as a viable dark matter candidate. In this paper we consider a scenario in which the dark matter particle is at the keV-scale. Such particle is free from X-ray limits due to the unbroken parity symmetry that forbids the mixing between active and right-handed neutrinos. The active neutrino masses are radiatively generated from the new scalars and the two heavier right-handed states with ∼ mathcal{O} (100) GeV masses. These heavy fermions can produce the observed baryon asymmetry of the Universe through the combination of Akhmedov-Rubakov-Smirnov mechanism and recently proposed scalar decays. To the best of our knowledge, this is the first time that these two mechanisms are shown to be successful in any radiative model. We identify the parameter space where the successful leptogenesis is compatible with the observed abundance of dark matter as well as the measurements from the neutrino oscillation experiments. Interestingly, combining dark matter production and successful leptogenesis gives rise to strict limits from big bang nucleosynthesis which do not allow the mass of dark matter to lie above ∼ 10 keV, providing a phenomenological hint for considered low-scale dark matter. By featuring the keV-scale dark matter free from stringent X-ray limits, successful baryon asymmetry generation and non-zero active neutrino masses, the model is a direct analogue to the νMSM model proposed by Asaka, Blanchet and Shaposhnikov. Therefore we dub the presented framework as “The new νMSM” abbreviated as ννMSM.

A spin-1 representation for dual-funnel energy landscapes.

The interconversion between the left- and right-handed helical folds of a polypeptide defines a dual-funneled free energy landscape. In this context, the funnel minima are connected through a continuum of unfolded conformations, evocative of the classical helix-coil transition. Physical intuition and recent conjectures suggest that this landscape can be mapped by assigning a left- or right-handed helical state to each residue. We explore this possibility using all-atom replica exchange molecular dynamics and an Ising-like model, demonstrating that the energy landscape architecture is at odds with a two-state picture. A three-state model-left, right, and unstructured-can account for most key intermediates during chiral interconversion. Competing folds and excited conformational states still impose limitations on the scope of this approach. However, the improvement is stark: Moving from a two-state to a three-state model decreases the fit error from 1.6 kBT to 0.3 kBT along the left-to-right interconversion pathway.

Low-coherence interferometry for phase-sensitive measurement of optical rotation.

We present phase-sensitive measurement of optical rotation using spectral-domain and time-domain low-coherence interferometry. The method utilizes two decorrelated polarization states and simultaneous dual-channel detection provided by polarization-maintaining fiber-based implementation. The sample is placed between polarization optics to control and switch left- and right-handed circular states that experience the sample in forward and backward directions. Phase difference between two interferometric signals yields the optical rotation. Results from glucose and fructose samples are presented for validation.

Topological semimetal in honeycomb lattice LnSI

Recognized as elementary particles in the standard model, Weyl fermions in condensed matter have received growing attention. However, most of the previously reported Weyl semimetals exhibit rather complicated electronic structures that, in turn, may have raised questions regarding the underlying physics. Here, we report promising topological phases that can be realized in specific honeycomb lattices, including ideal Weyl semimetal structures, 3D strong topological insulators, and nodal-line semimetal configurations. In particular, we highlight a semimetal featuring both Weyl nodes and nodal lines. Guided by this model, we showed that GdSI, the long-perceived ideal Weyl semimetal, has two pairs of Weyl nodes residing at the Fermi level and that LuSI (YSI) is a 3D strong topological insulator with the right-handed helical surface states. Our work provides a mechanism to study topological semimetals and proposes a platform for exploring the physics of Weyl semimetals as well as related device designs.

Measurement of the W boson polarisation in tbar{t} events from pp collisions at sqrt{s} = 8 TeV in the lepton\xa0+\xa0jets channel with ATLAS

This paper presents a measurement of the polarisation of W bosons from tbar{t} decays, reconstructed in events with one high-p_{text{ T }} lepton and at least four jets. Data from pp collisions at the LHC were collected at sqrt{s} = 8 TeV and correspond to an integrated luminosity of 20.2 fb^{-1}. The angle theta ^{*} between the b-quark from the top quark decay and a direct W boson decay product in the W boson rest frame is sensitive to the W boson polarisation. Two different W decay products are used as polarisation analysers: the charged lepton and the down-type quark for the leptonically and hadronically decaying W boson, respectively. The most precise measurement of the W boson polarisation via the distribution of cos {theta ^{*}} is obtained using the leptonic analyser and events in which at least two of the jets are tagged as b-quark jets. The fitted fractions of longitudinal, left- and right-handed polarisation states are F_{mathrm {0}}=~0.709~pm ~{0.019}, F_{mathrm {L}}=~0.299~pm ~{0.015} and F_{mathrm {R}}=~-0.008~pm ~{0.014}, and are the most precisely measured W boson polarisation fractions to date. Limits on anomalous couplings of the Wtb vertex are set.

T-Shaped Probe Waveguide Antenna: A Wideband Reconfigurable Circular-Polarized Single-Port Antenna

We propose a wideband reconfigurable circular-polarized single-port antenna to realize high-density linear integration for use in ground penetrating radars. We switch PIN diodes at a T-shaped probe to change its polarization. The forward- and reverse-biased probes work in cooperation to generate circular polarization. Experiments demonstrate the working bandwidths of 20.0% and 18.6% in the left- and right-hand polarization states, respectively, with 7.2 GHz center frequency. They are wider than those of conventional reconfigurable single-port circular-polarized antennas.

Chiral optical response of planar and symmetric nanotrimers enabled by heteromaterial selection.

Chirality is an intriguing property of certain molecules, materials or artificial nanostructures, which allows them to interact with the spin angular momentum of the impinging light field. Due to their chiral geometry, they can distinguish between left- and right-hand circular polarization states or convert them into each other. Here we introduce an approach towards optical chirality, which is observed in individual two-dimensional and geometrically mirror-symmetric nanostructures. In this scheme, the chiral optical response is induced by the chosen heterogeneous material composition of a particle assembly and the corresponding resonance behaviour of the constituents it is built from, which breaks the symmetry of the system. As a proof of principle, we investigate such a structure composed of individual silicon and gold nanoparticles both experimentally, as well as numerically. Our proposed concept constitutes an approach for designing two-dimensional chiral media tailored at the nanoscale, allowing for high tunability of their optical response.

Axion inflation with an SU(2) gauge field: detectable chiral gravity waves

We study a single field axion inflation model in the presence of an SU(2) gauge field with a small vev. In order to make the analysis as model-independent as possible, we consider an arbitrary potential for the axion that is able to support the slow-roll inflation. The gauge field is coupled to the axion with a Chern-Simons interaction $$ \frac{\lambda }{f}{F}_{\mu \nu}^a{\tilde{F}}_a^{\mu \nu } $$ where $$ \frac{\lambda }{f}\sim \frac{\mathcal{O}(10)}{M_{\mathrm{pl}}} $$ . It has a negligible effect on the background evolution, $$ \frac{\rho \mathrm{Y}\mathrm{M}}{M_{\mathrm{pl}}^2{H}^2}\lesssim {\upepsilon}^2 $$ . However, its quantum fluctuations make a significant contribution to the cosmic perturbation. In particular, the gauge field has a spin-2 fluctuation which explicitly breaks the parity between the left- and right-handed polarization states. The chiral tensor modes are linearly coupled to the gravitational waves and lead to a circularly polarized tensor power spectrum comparable to the unpolarized vacuum power spectrum. Moreover, the scalar sector is modified by the linear scalar fluctuations of the gauge field. Since the spin-0 and spin-2 fluctuations of the SU(2) gauge field are independent, the gauge field can, at the same time, generate a detectable chiral gravitational wave signal and have a negligible contribution to the scalar fluctuations, in agreement with the current CMB observations.

Investigating the Handedness Dynamics of Tetrasomes

Nucleosomes formed by DNA wrapping around histone octamers are the basic compaction unit of eukaryotic chromatin. Besides packaging DNA, they also play an essential role in genome regulation by controlling DNA accessibility. Their assembly follows a precise pathway in which first tetramers of H3 and H4 histones bind to DNA, forming tetrasomes, and then two dimers of H2A and H2B histones complete the formation of full nucleosomes. Here, we present our single-molecule studies on the assembly of tetrasomes by directly measuring the length, twist, and torque of single DNA molecules using Freely Orbiting Magnetic Tweezers (FOMT) and electro-Magnetic Torque Tweezers (eMTT). By this means, we have investigated both the replication-coupled histone H3.1 and its replication-independent variant histone H3.3. Our results indicate that tetrasomes exhibit a spontaneous flipping between a preferentially occupied left-handed state (ΔLk = −0.73) and a less populated right-handed state (ΔLk = +1.0), while weak torques convert them from one state into the other. In addition, the stepwise assembly of full nucleosomes suggests that tetrasomes undergoing changes in handedness remain viable intermediates. We further show how studies performed on tetrasomes that are artificially modified at their H3-H3 interface provide more insight into their handedness dynamics. Our findings reveal dynamical rearrangements of the nucleosomal structure that illustrate how chromatin could regulate DNA-supercoiling.

Collective model of chiral and wobbling modes in nuclei

Recent progress of collective Hamiltonian for the chiral and wobbling modes in nuclei is reviewed. A brief introduction about the experimental and theoretical research statuses of the chirality and wobbling is given first. Procedures of constructing collective Hamiltonian, based on the tilted axis cranking approach, are shown in details. The newly developed collective Hamiltonian is used to investigate the chiral and wobbling modes. For the chiral modes, we study the microscopic mechanism of the energy difference between the chiral doublets with respect to the rotational frequency. It is demonstrated that the gradually increased potential barrier suppresses the tunneling probabilities between the left- and right-handed states and thus causes the decreasing of the energy difference. For the wobbling modes, the variation trends of wobbling frequencies for simple, longitudinal, and transverse wobblers are studied and found to be related to the stiffness of the collective potential.

Higgs-like mechanism for spontaneous spacetime symmetry breaking

The study of spontaneous breakdown of spacetime symmetries leads to the discovery of another type of Higgs mechanism operating in a chiral SU(2) model. Some of the Nambu-Goldstone vector mesons emergent from simultaneous violations of gauge and Lorentz symmetries are, in this case, absorbed by a left-handed doublet and endow one of the fermions with a right-handed state, while another part becomes emergent as photons. Accordingly, this mechanism allows a chiral fermion to acquire a mass, and it may enable the emergent theory to reproduce the electromagnetism equivalent to the QED sector in the standard theory. It is also mentioned that the "fermion-boson puzzle" known in the presence of a 't Hooft--Polyakov monopole does not exist in our theory.

Chiral symmetry in rotating systems

The triaxial rotating system at critical angular momentum I≥Iband exhibits two enatiomeric (the left- and right-handed) forms. These enatiomers are related to each other through dynamical chiral symmetry. The chiral symmetry in rotating system is defined by an operator χˆ=Rˆy(π)Tˆ, which involves the product of two distinct symmetries, namely, continuous and discrete. Therefore, new guidelines are required for testing its commutation with the system Hamiltonian. One of the primary objectives of this study is to lay down these guidelines. Further, the possible impact of chiral symmetry on the geometrical arrangement of angular momentum vectors and investigation of observables unique to nuclear chiral-twins is carried out. In our model, the angular momentum components (J1, J2, J3) occupy three mutually perpendicular axes of triaxial shape and represent a non-planar configuration. At certain threshold energy, the equation of motion in angular momentum develops a second order phase transition and as a result two distinct frames (i.e., the left- and right-handed) are formed. These left- and right-handed states correspond to a double well system and are related to each other through chiral operator. At this critical angular momentum, the centrifugal and Coriolis interactions lower the barrier in the double well system. The tunneling through the double well starts, which subsequently lifts the degeneracy among the rotational states. A detailed analysis of the behavior of rotational energies, spin-staggering, and the electromagnetic transition probabilities of the resulting twin-rotational bands is presented. The ensuing model results exhibit similarities with many observed features of the chiral-twins. An advantage of our formalism is that it is quite simple and it allows us to pinpoint the understanding of physical phenomenon which lead to chiral-twins in rotating systems.

Nucleosome Assembly Dynamics Involve Spontaneous Fluctuations in the Handedness of Tetrasomes

DNA wrapping around histone octamers generates nucleosomes, the basic compaction unit of eukaryotic chromatin. Nucleosome stability is carefully tuned to maintain DNA accessibility in transcription, replication, and repair. Using freely orbiting magnetic tweezers, which measure the twist and length of single DNA molecules, we monitor the real-time loading of tetramers or complete histone octamers onto DNA by Nucleosome Assembly Protein-1 (NAP1). Remarkably, we find that tetrasomes exhibit spontaneous flipping between a preferentially occupied left-handed state (ΔLk = -0.73) and a right-handed state (ΔLk = +1.0), separated by a free energy difference of 2.3 kBT (1.5 kcal/mol). This flipping occurs without concomitant changes in DNA end-to-end length. The application of weak positive torque converts left-handed tetrasomes into right-handed tetrasomes, whereas nucleosomes display more gradual conformational changes. Our findings reveal unexpected dynamical rearrangements of the nucleosomal structure, suggesting that chromatin can serve as a "twist reservoir," offering a mechanistic explanation for the regulation of DNA supercoiling in chromatin.

Nucleosome Assembly Dynamics Involve Spontaneous Fluctuations in the Handedness of Tetrasomes

Nucleosomes play crucial roles in eukaryotic cells as they form the basic compaction unit of DNA, and impact the accessibility of the DNA for transcription and replication. How the assembly, stability, and disassembly of nucleosomes affect the interplay between compaction and accessibility forms a question of key interest. Here we use freely-orbiting magnetic tweezers (FOMT), which can measure in real time the changes in length and twist of individually tethered DNA molecules. We monitor how Nucleosome Assembly Protein-1 (NAP1) loads either histone tetramers (an important intermediate in dis/assembly or remodeling) or complete histone octamers onto DNA, thus forming nucleosomes. Remarkably, tetrasomes are observed to exhibit a spontaneous flipping between DNA states with linking number ΔLk=-0.73 and ΔLk=+1.0, without concomitant changes in DNA end-to-end length. Such behavior is absent in the case of nucleosomes. The statistics of tetrasome flipping shows that the preferentially occupied left-handed state has a probability p=0.9. The difference in free energy between these two states is thus 2.3kBT. We also demonstrate how controlled application of positive torque can drive tetrasome occupancy from left-handed to right-handed states. To exclude effects of the assembly protein NAP1, we repeated these experiments with tetrasomes assembled in the conventional way using salt dialysis. These results show that the spontaneous fluctuations in the handedness of tetrasomes are not NAP1 induced. Since we expect the H3-H3 interface to play an important role in the handedness fluctuations, we also studied tetrasomes in which the replication-coupled canonical histone H3 was replaced by the replication-independent variant H3.3, which show very similar behavior. Our findings thus reveal unexpected dynamical rearrangements of the nucleosomal structure that suggest that chromatin can serve as a ‘twist reservoir’, offering a mechanistic explanation for the regulation of DNA supercoiling in chromatin.

On traveling waves in viscous-capillary Euler equations with thermal conductivity

This work establishes the stability of the equilibrium states corresponding to traveling waves in viscous-capillary Euler equations when a standard thermal conductivity coefficient is present. Due to the presence of the heat conduction, the associated system of ordinary differential equations is much more involved and complicated. Given a shock wave, we can obtain exactly the sign of the real part of each eigenvalue of the Jacobian matrix of the corresponding system of ODEs at the two equilibria associated with the left-hand and right-hand states of the shock. It turns out that one equilibrium point is asymptotically stable, why the other point is unstable and admits eigenvalues whose real parts have opposite signs. Suitable approximate connections between the unstable and stable equilibria are obtained by numerical tests for various ranges of thermal conductivity: low, medium, and high values. Moreover, numerical tests also suggest that a trajectory could leave the unstable equilibrium point and enters the attraction domain of the asymptotically stable equilibrium point. This work therefore may motivate for further study on the existence of the traveling waves of the viscous-capillary gas dynamics equations with the presence of heat conduction.

Nucleosome Dynamics Involve Spontaneous Fluctuations in the Handedness of Tetrasomes

It is becoming increasingly clear that the dynamics of nucleosome assembly, stability and disassembly are of key importance for DNA compaction as well as for the control of the accessibility of the DNA for transcription and replication. Here we report a single-molecule study of the assembly of nucleosomes which reveals unexpected dynamic chiral fluctuations of tetrasomes. We use freely-orbiting magnetic tweezer (FOMT), which simultaneously report on the changes in twist and length of individually tethered DNA molecules, to monitor the loading of either (H3-H4)2 tetramers or complete histone octamers onto DNA by Nucleosome Assembly Protein-1 (NAP1). We find that the DNA undergoes a change in linking number ΔLk of −0.73 ± 0.05 per assembled tetramer, and a change in linking number of −1.2 ± 0.3 turns per assembled nucleosome. Remarkably, in the absence of applied torque tetrasomes, but not nucleosomes, undergo spontaneous flipping between a preferentially occupied left-handed state (ΔLk = −0.73) and a right-handed state (ΔLk = +1.0), separated by a free energy difference of −2.3 kBT. This spontaneous flipping occurs without concomitant changes in DNA end-to-end length. Controlled application of positive torque can convert tetrasomes that occupy left-handed states into tetrasomes that occupy right-handed states, while nucleosomes subjected to torques up to 11 pN·nm do not change chirality. These dynamics suggest that the removal of the outer histones H2A and H2B, e.g. by remodelers like NAP1, lay bare a dynamic tetrasome. This tetrasome can readily accommodate the build-up of positive torque, e.g. ahead of elongating RNA polymerases, through conformational changes. Thus, our findings reveal a new dynamical rearrangement of nucleosomes that offers a mechanistic explanation for the control of DNA supercoiling upon processing of chromatin in the cell.

From Generalized Dirac Equations to a Candidate for Dark Energy

We consider extensions of the Dirac equation with mass terms m1+iγ5m2 and im1+γ5m2. The corresponding Hamiltonians are Hermitian and pseudo-Hermitian (γ5 Hermitian), respectively. The fundamental spinor solutions for all generalized Dirac equations are found in the helicity basis and brought into concise analytic form. We postulate that the time-ordered product of field operators should yield the Feynman propagator (iϵ prescription), and we also postulate that the tardyonic as well as tachyonic Dirac equations should have a smooth massless limit. These postulates lead to sum rules that connect the form of the fundamental field anticommutators with the tensor sums of the fundamental plane-wave eigenspinors and the projectors over positive-energy and negative-energy states. In the massless case, the sum rules are fulfilled by two egregiously simple, distinguished functional forms. The first sum rule remains valid in the case of a tardyonic theory and leads to the canonical massive Dirac field. The second sum rule is valid for a tachyonic mass term and leads to a natural suppression of the right-handed helicity states for tachyonic particles and left-handed helicity states for tachyonic spin-1/2 antiparticles. When applied to neutrinos, the theory contains a free tachyonic mass parameter. Tachyons are known to be repulsed by gravity. We discuss a possible role of a tachyonic neutrino as a contribution to the accelerated expansion of the Universe “dark energy.”

Consistent histories for tunneling molecules subject to collisional decoherence

The decoherence of a two-state tunneling molecule, such as a chiral molecule or ammonia, due to collisions with a buffer gas is analyzed in terms of a succession of quantum states of the molecule satisfying the conditions for a consistent family of histories. With $\hbar \omega$ the separation in energy of the levels in the isolated molecule and $\gamma$ a decoherence rate proportional to the rate of collisions, we find for $\gamma \gg \omega$ (strong decoherence) a consistent family in which the molecule flips randomly back and forth between the left- and right-handed chiral states in a stationary Markov process. For $\gamma < \omega$ there is a family in which the molecule oscillates continuously between the different chiral states, but with occasional random changes of phase, at a frequency that goes to zero at a phase transition $\gamma = \omega$. This transition is similar to the behavior of the inversion frequency of ammonia with increasing pressure, but will be difficult to observe in chiral molecules such as D$_2$S$_2$. There are additional consistent families both for $\gamma > \omega$ and for $\gamma < \omega$. In addition we relate the speed with which chiral information is transferred to the environment to the rate of decrease of complementary types of information (e.g., parity information) remaining in the molecule itself.

MEMS-tunable composite right/left-handed (CRLH) transmission line and its application to a phase shifter

This paper reports a novel compact tunable composite right/left-handed transmission line (CRLH TL) with multi-state phase tunability using integrated microelectromechanical system (MEMS) switches and its application to a phase shifter. It is possible to select multiple states with different positive/negative phase responses. The phase states can be determined by controlling the admittance of capacitors and impedance of inductors through MEMS switch operations. The designed devices are analyzed using electromagnetic and circuit simulations. The propagation characteristics and phase lead/lag properties of the devices are investigated. The designed device can be operated as a 90°/−90° phase tunable CRLH TL at 8 GHz and a four-state phase shifter at 9.5 GHz by switch configuration. At 8 GHz, the phase responses of the device were 87° of the phase lead and −80° of the phase lag for the left-handed (LH) and right-handed (RH) states, respectively. At 9.5 GHz, the phase of each state varies among 26.7°, 14.6°, −6.7°, and −11.5°, where the first two states are in the LH region and the others are in the RH region. At 9–15 GHz, insertion losses are measured to be <2.6 dB, and return losses are >10 dB.

Wash-out in N2-dominated leptogenesis

We study the wash-out of a cosmological baryon asymmetry produced via leptogenesis by subsequent interactions. Therefore we focus on a scenario in which a lepton asymmetry is established in the out-of-equilibrium decays of the next-to-lightest right-handed neutrino. We apply the full classical Boltzmann equations without the assumption of kinetic equilibrium and including all quantum statistical factors to calculate the wash-out of the lepton asymmetry by interactions of the lightest right-handed state. We include scattering processes with top quarks in our analysis. This is of particular interest since the wash-out is enhanced by scatterings and the use of mode equations with quantum statistical distribution functions. In this way we provide a restriction on the parameter space for this scenario.