Modern Physics Letters A

Quantum Private Information Retrieval (QPIR) allows a user (Alice) to retrieve a database item from the database owned by the database holder (Bob) in such a way that Alice can query only the database item she wants, but cannot get other items, and Bob does not know which item Alice queries. However, the real quantum channel between Alice and Bob is noisy, and the noise may result in not only the chance that Alice obtains a false item, but also that both parties may cheat by camouflaging themselves with noise. In this paper, we use the decoherence-free subspace (DFS) for QPIR, which we call DFS-QPIR. The DFS-QPIR protocol removes the effect of the channel noise on the errors in the retrieved item so that two parties cannot cheat by replacing the noisy channel with a noiseless one. It can work over a collective noisy channel while retaining high reliability, database security and user privacy simultaneously. While only the collective unitary noise is taken into account, the proposed DFS-QPIR protocol can be straightforwardly extended to more general collective noise channel.

In this paper, we revisit the classical mechanism to produce $d$-dimensional spacetimes via Kaluza–Klein compactification. We made the assumption that the $(d+1)$-dimensional bulk geometry ${ℳ}$ admits a Homothetic Vector Field (HVF) $H$ relaxing the existence of a zero i.e. $H\ne 0$ holds on ${ℳ}$ and the homothetic bivector $F_{ab}(H)=0$. Under these circumstances, we identify the origin of a positive cosmological constant in the $d$-dimensional spacetime as the homothetic factor representing a geometrical artifact of late time state of the $(d+1)$-dimensional bulk spacetime.

In this work, after introducing the main algebraic and representative properties of the quantum mechanics with Dunkl derivative, two-particle system with exchange symmetry is studied. In this framework, a new deformed derivative involving the exchange operator is proposed. With the help of such an operator, the new deformed quantum theory for systems with two quantum particles in one dimension is developed. As physical applications of the present construction, systems with two quantum particles interacting via the harmonic potential and the delta-function potential well are considered in detail. The wave functions and the energy spectra for these potentials are derived. Finally, possible implications of our results on other application areas of research such as in interacting theories of either bosons or fermions are concisely discussed.

The effect of the nucleon coupling constants on the mass radius ratio (further, the surface gravitational redshift) of proto neutron star (PNS) PSR J0737-3039A is examined with relativistic mean field theory in consideration of a baryon octet. Here, five sets of nucleon coupling constants DD-MEI, GL85, GL97, GM1 and NL2 are used. The PNS’s temperature is assumed to be $T=20$ MeV and the mass the PNS PSR J0737-3039A is chosen as $M=1.338M_{\odot }$. The radius and the mass radius ratio of the PNS PSR J0737-3039A calculated by the five groups of nucleon coupling constants above are $R=15.693\text{–}18.846$ km and $M/R=0.071\text{–}0.085M_{\odot }$/km, respectively. The surface gravitational redshift $z$ of the PNS PSR J0737-3039A calculated from the above five groups of nucleon coupling constants is $z=0.125\text{–}0.156$.

In this paper, we introduce the formalism to examine the impact of the dark scalar sector to the conformal and the electroweak symmetries breaking in the sense of formation of the scalar boson star (BS). The BS is presented by the local scalar field containing the Higgs boson field and the scalar dilaton field in the conformal field theory. We study in detail the modification of the Higgs quartic coupling away from its Standard Model (SM) value within the influence of the dark sector. We show that the repulsive self-interactions and the flatness degree in the dark scalar sector can prevent an instability and the destruction of the BS. We have estimated the rate of the deviation from the SM with production of leptonic pairs due to decays of dilatons and dark photons emerged because of the BS instability. The lifetime, the maximal mass and the density of the BS, the average minimal distance between the stars are estimated. The effects of new physics should be visible at the HL-LHC, FCC-hh accompanied by the current LHC and the cosmological data.

We study the $B\to K^{(\ast )}\nu \bar{\nu }$ decays within the Standard Model (SM) by using the relevant transition form factors obtained from the covariant confined quark model (CCQM) developed by us. The $B\to K$ and $B\to K^{\ast }$ transition form factors are calculated in the full kinematic $q^2$ range. The branching fractions are then calculated. It is shown that our results are in an agreement with those obtained in other theoretical approaches. Currently, the BaBar and Belle collaborations provide us by the upper limits at 90% confidence limit. The obtained bounds are roughly an order of magnitude larger than the SM predictions. This should stimulate experimental collaborations to set up experiments that allow one to obtain more accurate branching values, which is quite achievable on the updated LHCb and Belle machines. If the discrepancies between theory and experiment are confirmed, this will open up opportunities for constructing models with new particles and interactions leading to an extension of the SM.

Considering the visible and the PeV photons from SN1054 to be emitted at similar times at the source, one estimates the value of a fundamental time constant $\tau$ arising in the noncommutative spacetime formulation.