arXiv subjects

Daniil Krichevskiy

Publications and source records attributed to Daniil Krichevskiy.

7 recordsLinked to original sources

arXiv2026

QCD-like theories at next-to-next-to-leading order with $N_F=2$ non-degenerate fermions

QCD-like theories with $N_F=2$ fermion flavours in real and pseudoreal representations are studied within Chiral Perturbation Theory. For the pseudoreal symmetry-breaking pattern $SU(4)/Sp(4)$, the reduced NLO Lagrangian is derived. The NLO and NNLO corrections to the pion masses, decay constants, and vacuum condensates are calculated for non-degenerate fermion masses, extending previous results obtained for degenerate masses and for the non-degenerate case at NLO. Using the available spectroscopic and scattering lattice data for the $Sp(N_c=4)$ gauge theory with two fermion flavours, fits of the NLO low-energy constants are performed at NNLO precision. It is found that higher-order corrections are important for reproducing lattice observables and have a significant impact on the phenomenology of strongly interacting pionic dark matter, particularly in the regime of big $M_π/F_π$.

hep-ph↗

arXiv2026

NLO observables for QCD-like theories and application to pion dark matter

QCD-like theories are of interest in various areas of beyond-Standard-Model phenomenology, including composite Higgs models or pionic dark matter. The effective field theories provide a framework for describing the dynamics of such strongly coupled gauge theories at low energies. In this work, we present next-to-leading order (NLO) expressions for masses, condensates, decay constants, and scattering amplitudes in the chiral expansion of QCD-like theories with $N_F=2$ fermions with non-degenerate masses in both real and pseudoreal representations of the gauge group. We further apply the NLO formulas to fit existing lattice spectroscopic and scattering data for $Sp(N_c=4)$ gauge theory with $N_F=2$ fermions in fundamental representation, extracting the NLO low-energy constants of the theory. Using these fits, we refine the NLO formulas describing the $2\to 2$ pion self-interactions and confirm that the NLO contributions play a crucial role in determining the viable parameter space of pion dark matter scenarios like the strongly interacting massive particles (SIMP).

hep-ph↗

arXiv2024

The unitary Fermi gas at large charge and large N

We study the unitary Fermi gas in a harmonic trapping potential starting from a microscopic theory in the limit of large charge and large number of fermion flavors N. In this regime, we present an algorithmic procedure for extracting data from perturbation theory, order-by-order, without the need for other assumptions. We perform a gradient expansion in the interior of the particle cloud, sufficiently far from the cloud edge where the particle density drops rapidly to zero. In this latter region we present the first microscopic computation characterizing the contribution of the edge terms. The microscopic theory reproduces the predictions of the superfluid EFT, including the action, the form of the gap equation, and the energy of the system in a harmonic trap (which maps, via the non-relativistic state-operator correspondence, to the scaling dimension of the lowest operator of charge Q). We additionally give the Wilsonian coefficients at leading order in N up to NNLO in the large-charge expansion.

hep-th↗

arXiv2022

Black holes and the nature of the event horizon

The problem of the event horizon in relativistic gravity is discussed. Singular solutions in general relativity are well known. The Schwarschild metric of a spherical mass is singular at zero ($r = 0$) and at the event horizon ($r = r_g$). Both features reflect the existence of the phenomenon of collapse in general relativity for compact masses exceeding $3M_{\odot }$. A material particle crossing the event horizon falls into a central singularity according to the classical theory of general relativity. In the quantum theory of gravity, there may be no central singularity. The physics of the event horizon is currently being refined. A promising technique is the study of gravitational waves (GW) accompanying the merger of binary black holes at the ringdown stage. GW observations of quasi-normal modes of the newly formed super dense remnant will help clarify the physics of the event horizon.

gr-qc↗

arXiv2022

Search for gravitational-neutrino correlations on ground-based detectors

The problem of joint data processing from ground-based gravitational and neutrino detectors is considered in order to increase the detection efficiency of collapsing objects in the Galaxy. The development of the "neutrino - gravitational correlation" algorithm is carried out within the framework of the theory of optimal filtration as applied to the well-known OGRAN and BUST facilities located at the BNO INR RAS. The experience of analyzing neutrino and gravitational data obtained during the outburst of supernova SN1987A is used. Sequential steps of the algorithm are presented, formulas for estimating the statistical efficiency of a two-channel recorder are obtained.

gr-qc↗

arXiv2021

Gravity models with nonlinear symmetry realization

Three models with nonlinear realizations of conformal symmetry are discussed. The simplest model can only describe a universe expanding with a deceleration and does not include inflation. The other models are equivalent up to a variables reparametrization. All these models contain ghost degrees of freedom which may be excluded with an additional symmetry of the target space.

gr-qc↗

arXiv2021

Optimization of the Euro-Asian network of gravitational detectors for detecting the radiation of collapsing objects

A Euro-Asian network of four gravitational-wave (GW) interferometers is considered, taking into account the plan to create such a detector in Novosibirsk. The efficiency of the network is assessed by typical numerical criteria, which also depend on the characteristics of the received signal. In this work, we calculate the optimal orientation of the Novosibirsk detector for the problem of detecting GW radiation accompanying the collapse of the progenitor star with an initial angular momentum. The specificity of the scenario is the presence of the so-called. bar stage deformation, for which the shape of the emitted GW signal is known.

gr-qc↗