We consider the effects of a perpendicular magnetic field on the d-density wave order and conclude that if the pseudogap phase in the cuprates is due to this order, then it is highly insensitive to the magnetic field in the underdoped regime, while its sensitivity increases as the gap vanishes in the overdoped regime. This appears to be consistent with the available experiments and can be tested further in neutron scattering experiments. We also investigate the nature of the de Haas-van Alphen effect in the ordered state and discuss the possibility of observing it. PACS numbers:Recently it was argued 1,2 that the observed pseudogap in the cuprate superconductors is due to the development of a second type of order, the d-density wave order (DDW), which is a particle-hole condensate with an internal "angular momentum" 2. The notion of this broken symmetry has allowed us to understand an array of experiments, although a priori there is no sense in which such a state is close to, or adiabatically continuable to, a superconductor, or a Fermi liquid, which are the two most prominent states of matter.From considerations of the simplest Hartree-Fock Hamiltonian that captures the broken symmetry of the DDW and the electromagnetic gauge invariance, we study the dependence of the DDW order parameter as a function of the applied magnetic field perpendicular to CuO-planes. We find that the effect of the magnetic field on the pseudogap is rather weak, if the DDW order is well-developed. For example, to destroy a DDW gap of magnitude of order 20 meV would require fields of order 1000 T, or larger. Moreover, this gap is highly insensitive to fields of order 25 T. This is, of course, a characteristic of the underdoped regime. In the overdoped regime, where the DDW gap drops rapidly to zero, the dependence on the magnetic field could be substantial.We suggest that the recent neutron scattering experiments, which report a tantalizing evidence of DDW order 3 in the form of a resolution-limited elastic Bragg peak at the in-plane wave vector (π/a, π/a), where a is the lattice spacing, should be carefully examined for its dependence on a perpendicular magnetic field. The prediction is that the Bragg scattering intensity will be hardly affected, if the zero temperature DDW gap is substantial. 4The effect of magnetic field on a superconductor is well known. Since the Cooper pairs involve time reversed mates, the effect of any time reversal breaking perturbation is very important. In contrast, the particle-hole pairs of the same spin orientation form the DDW condensate, and, as a consequence, such a condensate is inherently less affected by a magnetic field.The contrasting response of a d-wave superconductor (DSC) and a DDW to applied magnetic field is further illuminated by examining the nodal quasiparticles of these two systems. The nodal quasiparticles of a DSC do not form Landau levels, 5 while those of a DDW state do. 6This implies that, in principle, it is possible to observe de Haas-van Alphen (dHvA) oscillations in a DDW state, b...

Two dimensional electron systems exhibiting the fractional quantum Hall effects are characterized by a quantized Hall conductance and a dissipationless bulk. The transport in these systems occurs only at the edges of the incompressible quantum Hall regions, where gapless excitations are present. We present a microscopic calculation of the edge states in the fractional quantum Hall systems at various filling factors using the extended Hamiltonian theory of the fractional quantum Hall effect. We find that at ν = 1/3 the quantum Hall edge undergoes a reconstruction as the background potential softens, whereas quantum Hall edges at higher filling factors, such as ν = 2/5, 3/7, are robust against reconstruction. We present the results for the dependence of the edge states on various system parameters such as temperature, functional form and range of electron-electron interactions, and the confining potential. Our results have implications for the tunneling experiments into the edge of a fractional quantum Hall system.

The special Buchdahl-inspired metric obtained in a recent paper [Phys. Rev. D 107, 104008 (2023)] describes asymptotically flat spacetimes in pure $$\mathcal {R}^{2}$$ R 2 gravity. The metric depends on a new (Buchdahl) parameter $$\tilde{k}$$ k ~ of higher-derivative characteristic, and recovers the Schwarzschild metric when $$\tilde{k}=0$$ k ~ = 0 . It is shown that the special Buchdahl-inspired metric supports a two-way traversable Morris–Thorne wormhole for $$\tilde{k}\in (-1,0)$$ k ~ ∈ ( - 1 , 0 ) in which case the Weak Energy Condition is formally violated, a naked singularity for $$\tilde{k}\in (-\infty ,-1)\cup (0,+\infty )$$ k ~ ∈ ( - ∞ , - 1 ) ∪ ( 0 , + ∞ ) , and a non-Schwarzschild structure for $$\tilde{k}=-1$$ k ~ = - 1 .

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Text-To-Speech (TTS) was one of nine shared tasks in the eighth annual international VLSP 2021 workshop. All three previous TTS shared tasks were conducted on reading datasets. However, the synthetic voices were not natural enough for spoken dialog systems where the computer must talk to the human in a conversation. Speech datasets recorded in a spontaneous environment help a TTS system to produce more natural voices in speaking style, speaking rate, intonation... Therefore, in this shared task, participants were asked to build a TTS system from a spontaneous speech dataset. This 7.5-hour dataset was collected from a channel of a famous youtuber "Giang ơi..."and then pre-processed to build utterances and their corresponding texts. Main challenges at this task this year were: (i) inconsistency in speaking rate, intensity, stress and prosody across the dataset, (ii) background noises or mixed with other voices, and (iii) inaccurate transcripts. A total of 43 teams registered to participate in this shared task, and finally, 8 submissions were evaluated online with perceptual tests. Two types of perceptual tests were conducted: (i) MOS test for naturalness and (ii) SUS (Semantically Unpredictable Sentences) test for intelligibility. The best SUS intelligibility TTS system had a syllable error rate of 15%, while the best MOS score on dialog utterances was 3.98 over 4.54 points on a 5-point MOS scale. The prosody and speaking rate of synthetic voices were similar to the natural one. However, there were still some distorted segments and background noises in most of TTS systems, a half of which had a syllable error rate of at least 30%.