Korea Institute for Advanced Study (KIAS)
Researchers developed "Direct Unlearning Optimization (DUO)", an image-based unlearning framework for Text-to-Image models. DUO directly removes unsafe visual concepts like nudity and violence, demonstrating superior robustness against red teaming attacks while preserving the model's general generative quality, and successfully generalized to Stable Diffusion 3.
We apply an extended Alcock-Paczyński (AP) test to the Sloan Digital Sky Survey data to constrain the dark energy models with the Chevallier-Polarski-Linder (CPL) parametrization of the dark energy equation of state. The extended AP test method uses the full shape of redshift-space two-point correlation funcion(CF) as the standard shape in order to measure the expansion history of the universe. We calibrate the standard shape by using the cosmology-dependent nonlinear evolution of the CF shape in the Multiverse simulations. Further validation of the method and calibration of possible systematics are performed based on mock samples from the Horizon Run 4 simulation. Using the AP test alone, we constrain the flat CDM plus CPL-type dark energy model (flat wCPLw^{\rm CPL}CDM) to have Ωm=0.2890.029+0.031\Omega_m=0.289_{-0.029}^{+0.031}, w0=0.7980.102+0.192w_0=-0.798_{-0.102}^{+0.192} and wa=0.1650.945+0.610w_a=-0.165_{-0.945}^{+0.610}. The result does not show evidence for a dynamically evolving dark energy model. When combined with other results from the low-redshift universe, such as the PantheonPlus supernova compilation and DESI BAO data, the constraint on waw_a becomes wa=0.1240.368+0.334w_a=-0.124_{-0.368}^{+0.334}, which is still consistent with zero.
The efficiency of adiabatic quantum evolution is governed by the adiabatic evolution time, TT, which depends on the minimum energy gap, Δ\Delta. For a generic schedule, TT typically scales as Δ2\Delta^{-2}, whereas the rigorous lower bound is O(Δ1)\mathcal{O}(\Delta^{-1}). This indicates the potential for a quadratic speedup through the adiabatic schedule construction. Here, we introduce the constant speed schedule, which traverses the adiabatic path of the eigenstate at a uniform rate. We first show that this approach reduces the scaling of the upper bound of the required evolution time by one order in 1/Δ1/\Delta. We then provide a segmented constant speed schedule protocol, in which path segment lengths are computed from eigenstate overlaps along the adiabatic evolution. By relying on the overlaps on the fly, our method eliminates the need for prior spectral knowledge. We test our algorithm numerically on the adiabatic unstructured search, the N2_2 molecule, and the [2Fe-2S] cluster. In our numerical experiments, the method achieves the optimal 1/Δ1/\Delta scaling in a small gap region, thereby demonstrating a quadratic speedup over the standard linear schedule.
The Quantum Approximate Optimisation Algorithm (QAOA) is a hybrid quantum-classical algorithm for solving combinatorial optimisation problems. QAOA encodes solutions into the ground state of a Hamiltonian, approximated by a pp-level parameterised quantum circuit composed of problem and mixer Hamiltonians, with parameters optimised classically. While deeper QAOA circuits can offer greater accuracy, practical applications are constrained by complex parameter optimisation and physical limitations such as gate noise, restricted qubit connectivity, and state-preparation-and-measurement errors, limiting implementations to shallow depths. This work focuses on QAOA1_1 (QAOA at p=1p=1) for QUBO problems, represented as Ising models. Despite QAOA1_1 having only two parameters, (γ,β)(\gamma, \beta), we show that their optimisation is challenging due to a highly oscillatory landscape, with oscillation rates increasing with the problem size, density, and weight. This behaviour necessitates high-resolution grid searches to avoid distortion of cost landscapes that may result in inaccurate minima. We propose an efficient optimisation strategy that reduces the two-dimensional (γ,β)(\gamma, \beta) search to a one-dimensional search over γ\gamma, with β\beta^* computed analytically. We establish the maximum permissible sampling period required to accurately map the γ\gamma landscape and provide an algorithm to estimate the optimal parameters in polynomial time. Furthermore, we rigorously prove that for regular graphs on average, the globally optimal γR+\gamma^* \in \mathbb{R}^+ values are concentrated very close to zero and coincide with the first local optimum, enabling gradient descent to replace exhaustive line searches. This approach is validated using Recursive QAOA (RQAOA), where it consistently outperforms both coarsely optimised RQAOA and semidefinite programs across all tested QUBO instances.
The Hadrosymmetric Twin Higgs (HTH) model provides a natural solution to the little hierarchy problem by incorporating all three generations of quarks in a twin sector. Unlike other Twin Higgs scenarios, such as the Mirror Twin Higgs (MTH), the HTH framework avoids introducing additional light states or radiation and thus remains consistent with stringent bounds on the effective number of relativistic species, ΔNeff\Delta N_{\rm eff}. Its particle content and interactions also make it difficult to probe at colliders, highlighting the importance of cosmological tests. In this work, we study the cosmological implications of the HTH model, focusing on the persistent tensions in the Hubble constant (H0H_0) and the matter clustering amplitude (σ8\sigma_8). Implementing the HTH sector in a Boltzmann code and confronting it with cosmic microwave background (CMB) data and local H0H_0 measurements, we find that the scenario reduces the Hubble tension from more than 4σ4\sigma to about 2.5σ2.5\sigma, while also alleviating the σ8\sigma_8 discrepancy. These results demonstrate that the HTH framework not only addresses naturalness in particle physics but also offers a viable route to mitigating current cosmological tensions, thereby strengthening the link between fundamental theory and precision cosmology.
We present a new scheme to couple existing numerical methods for elastic self-interacting dark matter (SIDM) to the hydrodynamic equations via a continuous function of the local Knudsen number. The method, an SIDM-hydro hybrid (SHH), allows more efficient simulation of the evolution of inhomogeneous halos deep into the regime of gravothermal collapse. With the improved efficiency gained by moving to a hydrodynamical description in high-density regions, the SHH method allows central densities of two orders of magnitude higher to be reached in considerably less simulation time than traditional methods. Our implementation should be considered as the first step toward a robust SHH method, as we interpolate the first and second moments of the Boltzmann equation in the ideal-fluid limit only. The simulation results are qualitatively similar to those found with other methods, although there are differences in the implementation of the primary physics driving the dynamics, and in the details of the resulting halo profiles. However, our results indicate that the SHH technique shows promise to investigate gravothermal collapse in diverse, dynamical environments. The method can be extended to incorporate non-ideal fluid terms and dissipation, as needed for dark-matter scenarios where interactions beyond the elastic regime may be important in the dense interiors of some halos.
Conventional deep learning-based image reconstruction methods require a large amount of training data which can be hard to obtain in practice. Untrained deep learning methods overcome this limitation by training a network to invert a physical model of the image formation process. Here we present a novel untrained Res-U2Net model for phase retrieval. We use the extracted phase information to determine changes in an object's surface and generate a mesh representation of its 3D structure. We compare the performance of Res-U2Net phase retrieval against UNet and U2Net using images from the GDXRAY dataset.
Cosmic filaments are the channel through which galaxy groups assemble their mass. Cosmic connectivity, namely the number of filaments connected to a given group, is therefore expected to be an important ingredient in shaping group properties. The local connectivity is measured in COSMOS around X-Ray detected groups between redshift 0.5 and 1.2. To this end, large-scale filaments are extracted using the accurate photometric redshifts of the COSMOS2015 catalogue in two-dimensional slices of thickness 120 comoving Mpc centred on the group's redshift. The link between connectivity, group mass and the properties of the brightest group galaxy (BGG) is investigated. The same measurement is carried out on mocks extracted from the lightcone of the hydrodynamical simulation Horizon-AGN in order to control systematics. More massive groups are on average more connected. At fixed group mass in low-mass groups, BGG mass is slightly enhanced at high connectivity, while in high mass groups BGG mass is lower at higher connectivity. Groups with a star-forming BGG have on average a lower connectivity at given mass. From the analysis of the Horizon-AGN simulation, we postulate that different connectivities trace different paths of group mass assembly: at high group mass, groups with higher connectivity are more likely to have grown through a recent major merger, which might be in turn the reason for the quenching of the BGG. Future large-field photometric surveys, such as Euclid and LSST, will be able to confirm and extend these results by probing a wider mass range and a larger variety of environment.
We present an update on the calculation of BˉDνˉ\bar{B}\to D^\ast \ell \bar{\nu} semileptonic form factor at zero recoil using the Oktay-Kronfeld bottom and charm quarks on Nf=2+1+1N_f=2+1+1 flavor HISQ ensembles generated by the MILC collaboration. Preliminary results are given for two ensembles with a0.12a\approx 0.12 and 0.090.09 fm and Mπ310M_\pi\approx 310 MeV. Calculations have been done with a number of valence quark masses, and the dependence of the form factor on them is investigated on the a0.12a\approx 0.12 fm ensemble. The excited state is controlled by using multistate fits to the three-point correlators measured at 4--6 source-sink separations.
We provide a detailed study of gravitational reheating in quintessential inflation generalizing previous analyses only available for the standard case when inflation is followed by an era dominated by the energy density of radiation. Quintessential inflation assumes a common origin for inflation and the dark energy of the Universe. In this scenario reheating can occur through gravitational particle production during the inflation-kination transition. We calculate numerically the amount of the radiation energy density, and determine the temperature TT_* at which radiation starts dominating over kination. The value of TT_* is controlled by the Hubble parameter H0H_0 during inflation and the transition time Δt\Delta t, scaling as H02[ln(1/H0Δt)]3/4H_0^2 [\ln(1/H_0\Delta t)]^{3/4} for H0Δt1H_0 \Delta t \ll1 and H02(H0Δt)cH_0^2 (H_0 \Delta t)^{-c} for $H_0\Delta t \gg 1.Themodeldependentparameter. The model-dependent parameter c$ is found to be around 0.5 in two different parametrizations for the transition between inflation and kination.
We show that the 5D Nekrasov partition functions enjoy the enhanced global symmetry of the UV fixed point. The fiber-base duality is responsible for the global symmetry enhancement. For SU(2)SU(2) with Nf7N_f\leq 7 flavors the fiber-base symmetry together with the manifest flavor SO(2Nf)SO(2N_f) symmetry generate the ENf+1E_{N_f+1} global symmetry, while in the higher rank case the manifest global symmetry of the two dual theories related by the fiber-base duality map generate the symmetry enhancement. The symmetry enhancement at the level of the partition function is manifest once we chose an appropriate reparametrization for the Coulomb moduli.
We present an update on the calculation of BˉDνˉ\bar{B}\to D^\ast \ell \bar{\nu} semileptonic form factor at zero recoil using the Oktay-Kronfeld bottom and charm quarks on Nf=2+1+1N_f=2+1+1 flavor HISQ ensembles generated by the MILC collaboration. Preliminary results are given for two ensembles with a0.12a\approx 0.12 and 0.090.09 fm and Mπ310M_\pi\approx 310 MeV. Calculations have been done with a number of valence quark masses, and the dependence of the form factor on them is investigated on the a0.12a\approx 0.12 fm ensemble. The excited state is controlled by using multistate fits to the three-point correlators measured at 4--6 source-sink separations.
We examine how the mass assembly of central galaxies depends on their location in the cosmic web. The HORIZON-AGN simulation is analysed at z~2 using the DISPERSE code to extract multi-scale cosmic filaments. We find that the dependency of galaxy properties on large-scale environment is mostly inherited from the (large-scale) environmental dependency of their host halo mass. When adopting a residual analysis that removes the host halo mass effect, we detect a direct and non-negligible influence of cosmic filaments. Proximity to filaments enhances the build-up of stellar mass, a result in agreement with previous studies. However, our multi-scale analysis also reveals that, at the edge of filaments, star formation is suppressed. In addition, we find clues for compaction of the stellar distribution at close proximity to filaments. We suggest that gas transfer from the outside to the inside of the haloes (where galaxies reside) becomes less efficient closer to filaments, due to high angular momentum supply at the vorticity-rich edge of filaments. This quenching mechanism may partly explain the larger fraction of passive galaxies in filaments, as inferred from observations at lower redshifts.
In the standard Lambda-CDM paradigm, dwarf galaxies are expected to be dark-matter-rich, as baryonic feedback is thought to quickly drive gas out of their shallow potential wells and quench star formation at early epochs. Recent observations of local dwarfs with extremely low dark matter content appear to contradict this picture, potentially bringing the validity of the standard model into question. We use NewHorizon, a high-resolution cosmological simulation, to demonstrate that sustained stripping of dark matter, in tidal interactions between a massive galaxy and a dwarf satellite, naturally produces dwarfs that are dark-matter-deficient, even though their initial dark matter fractions are normal. The process of dark matter stripping is responsible for the large scatter in the halo-to-stellar mass relation in the dwarf regime. The degree of stripping is driven by the closeness of the orbit of the dwarf around its massive companion and, in extreme cases, produces dwarfs with halo-to-stellar mass ratios as low as unity, consistent with the findings of recent observational studies. ~30 per cent of dwarfs show some deviation from normal dark matter fractions due to dark matter stripping, with 10 per cent showing high levels of dark matter deficiency (Mhalo/M*<10). Given their close orbits, a significant fraction of dark-matter-deficient dwarfs merge with their massive companions (e.g. ~70 per cent merge over timescales of ~3.5 Gyrs), with the dark-matter-deficient population being constantly replenished by new interactions between dwarfs and massive companions. The creation of these galaxies is, therefore, a natural by-product of galaxy evolution and their existence is not in tension with the standard paradigm.
Recently the thermal friction on an expanding bubble from the cosmic first-order phase transition has been calculated to all orders of the interactions between the bubble wall and thermal plasma, leading to a γ2\gamma^2-scaling instead of the previously estimated γ1\gamma^1-scaling for the thermal friction exerted on a fast-moving bubble wall with a Lorentz factor γ\gamma. We propose for the first time the effective equation of motion (EOM) for an expanding bubble wall in the presence of an arbitrary γ\gamma-scaling friction to compute the efficiency factor from bubble collisions, which, in the case of γ2\gamma^2-scaling friction, is found to be larger than the recently updated estimation when the bubble walls collide after starting to approach a constant terminal velocity, leading to a slightly larger signal of the gravitational waves background from bubble collisions due to its quadratic dependence on the bubble collision efficiency factor, although the γ2\gamma^2-scaling friction itself has already suppressed the contribution from bubble collisions compared to that with γ1\gamma^1-scaling friction. We also suggest a phenomenological parameterization for the out-of-equilibrium term in the Boltzmann equation that could reproduce the recently found (γ21)(\gamma^2-1)-scaling of the friction term in the effective EOM of an expanding bubble wall, which merits further study in future numerical simulations of bubble expansion and collisions.
We investigate the electromagnetic transition form factors of the baryon decuplet to the baryon octet, based on the self-consistent SU(3) chiral quark-soliton model, taking into account the effects of explicit breaking of flavor SU(3) symmetry. We emphasize the Q2Q^2 dependence of the electromagnetic NΔN\to \Delta transition form factors and the ratios of E2/M1E2/M1 and C2/M1C2/M1 in comparison with the experimental and empirical data. In order to compare the present results of the electromagnetic transition form factors of the $N\to \Delta$ with those from lattice QCD, we evaluate the form factors with the pion mass deviated from its physical value. The results of the E2/M1E2/M1 and C2/M1C2/M1 ratios are in good agreement with the lattice data. We also present the results of the electromagnetic transition form factors for the decuplet to the octet transitions.
We investigate the mass spectra of the lowest-lying singly heavy baryons, based on the self-consistent chiral quark-soliton model. We take into account the rotational 1/Nc1/N_c and strange current quark mass (msm_{\mathrm{s}}) corrections. Regarding msm_{\mathrm{s}} as a small perturbation, we expand the effective chiral action to the second order with respect to msm_{s}. The mass spectra of heavy baryons are computed and compared with the experimental data. Fitting the classical masses of the heavy baryon to the center mass of each representation, we determine the masses of all the lowest-lying singly heavy baryons. We predict the mass of the Ωb\Omega_b^* baryon to be 6081.9 MeV, when the second-order msm_{\mathrm{s}} corrections are included.
The recent detection of a stochastic gravitational wave background (SGWB) at nanohertz frequencies by pulsar timing arrays (PTAs) has sparked a flurry of interest. Beyond the standard interpretation that the progenitor is a network of supermassive black hole binaries, many exotic models have also been proposed, some of which can potentially offer a better fit to the data. We explore how the various connections between gravitational waves and CMB spectral distortions can be leveraged to help determine whether a SGWB was generated primordially or astrophysically. To this end, we present updated kk-space window functions which can be used for distortion parameter estimation on enhancements to the primordial scalar power spectrum. These same enhancements can also source gravitational waves (GWs) directly at second order in perturbation theory, so-called scalar-induced GWs (SIGWs), and indirectly through the formation of primordial black holes (PBHs). We perform a mapping of scalar power spectrum constraints into limits on the GW parameter space of SIGWs for δ\delta-function features. We highlight that broader features in the scalar spectrum can explain the PTA results while simultaneously producing a spectral distortion (SD) within reach of future experiments. We additionally update PBH constraints from μ\mu- and yy-type spectral distortions. Refined treatments of the distortion window functions widen existing SD constraints, and we find that a future CMB spectrometer could play a pivotal role in unraveling the origin of GWs imprinted at or below CMB anisotropy scales.
A pion mean-field approach allows one to investigate light and singly heavy baryons on an equal footing. In the large NcN_c limit, the light and singly heavy baryons are viewed respectively as NcN_c and Nc1N_c-1 valence quarks bound by the pion mean fields created self-consistently, since a heavy quark can be regarded as a static color source in the limit of the infinitely heavy quark mass. The transition magnetic moments of the baryon sextet are determined entirely by using the parameters fixed in the light-baryon sector without any additional parameters introduced. Assuming that the transition E2E2 moments are small, we are able to compute the radiative decay rates of the baryon sextet. The numerical results are discussed, being compared with those from other approaches.
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